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CHAPTER

4

4.1 METHOD ADOPTED

4.1.1 TOOLS & TECHNIQUES EMPLOYED FOR THE STUDY

I

I

4.1.3 EXPERIMENTAL DESIGN & PROCEDURE 4.1.4 STATISTICAL TECHNIQUES APPLIED

i 1,

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/L.*

~. ..

L.,

..

,,

Methodology' . . ' .

.

.

METHODOLOGY

The details regarding the tools and techniques employed. method or procedure adopted for collecting data and the statistical techniques employed for the analysis of data are given below:

4.1

METHOD ADOPTED

The Investigator adopted Experimental cum Survey Method

for the present investigation. The details regarding the method / procedure adopted for collecting the data are given below under appropriate heads. 4.1.1

TOOLS AND TECHNIQUES EMPLOYED FOR THE

STUDY

The following tools were employed for collecting

necessary data.

(1) A Two-tier Diagnostic test in Chemistry for Educationally

Backward Students studying in standard IX (2) Remedial Teaching Materials in Chemistry for Educationally Backward Students on the following topics:

(i)

Periodic Table

Methodolow

(ii)

Atomic Structure

( i ~ i ) Oxidation & Reduction

(3)

Ach~evement test in Chemistry for students studying in Standard IX (used as pre and post tests)

(4)

Rating Scale for experts and Secondary School Chemistry Teachers

(5)

Questionnaire for Experts and Secondary School Chemistry teachers

(6)

General Data Sheet All the above mentioned tools were prepared by the

Investigator for the present study. The details regarding the tools used for the present study are given below:

1.

FI'\VO-TIEK DIAGNOSTIC ':ducationally Standard IX)

TEST

IN

CHEMISTRY

(for

Backward Students in Chemistry studying in

To construct a Diagnostic test, the Chemistry text books prescribed for Standards VIII. IX and X were thoroughly analysed and 6 3 learning points under different topics were listed. The list of learning points was given to experienced teachers and experts in Chemistry to get their opinion. According to their suggestions

Methodolow

some of the learning points were deleted, some were added and some were modified. Thus 50 learning points from seven different topics (Acids and Bases, Atomic Structure, Chemical Bonding, Language o f Chemistry, Oxidation & Reduction, Periodic Table, and Physical and Chemical Changes) were selected for the preparation of Diagnostic Test. (/ T*ble,.S.

+-~>:--.

I

').

On the basis of the teaching points (n = 50), Investigator prepared a Diagnostic Test having 50 multiple choice items, to collect details regarding the errors committed by the Educationally Backward students in Chemistry studying in Standard IX. The

items for the Diagnostic Test were based on the Two-tier multiple choice format described by ~ a m i r ' (1971). Tobin and capie2

(1981) and ~ r i ~ u (1986-1987). Each item has two tiers. The s t ~

first tler of each item consists of a content question having 4 choices. The student has to choose the most suitable answer

from the given 4 choices and make a tick mark in the answer sheet. The second tier of each item contains 4 possible reasons for the answer given in the first tier of the item. The student has to choose the most suitable reason for their answers for the first tier and make a tick mark in the answer sheet provided. The

answer to an item was considered correct if the student selected

.

Methodology

both the correct content choice and the correct reason. correct answer was given a score of one. Chppendix -1) The Investigator administered the

Each

Diagnostic Test

in

Chemistry to a sample of 620 Educationally Backward students studying in Standard IX. Out of 620, the scores of 370 students were taken for item analysis. Difficulty indices for the items

ranged from 0.09 to 0.7 showing a wide range of difficulty in the items. Discriminating powers ranged from 0.32 to 0.65 and all of (1971). them were considered acceptable according to ~ i e n ~ According to ~ i l b e r t ' (1977), work using multiple choice items with four or five choices, student understanding of the conceptual area was considered satisfactory if more than 75% of the students correctly answered the item. The items for which more than 75% of the students answered incorrectly were chosen as difficult items and the corresponding learning points were used for the

preparation of the Remedial Teaching Materials in Chemistry. The details regarding the learning points (included in the Remedial Teaching Materials in Chemistry) are given below:

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--

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-

Methodology

~

,.

. .. .

~

4

I

N~rcleusthe centrul part Electric charges of Electrons, Protons and Neutrons Cot~tributions towards the d i s c o v e r ~ f atomic ~ a r t i c l e s o

F -i'-JK~presettiaiion 11

1

o f a n aton, 111 I Oxidation And Reduction of Oxidation . . . . .. .. .. . - ' o f Reduction .. 3 Oxtdatlon based on Oxidation. ~ y .r .. .b.. - ...- . - .. - . n er . . . -I ' K ~ v l u ~ ~ ~ n xov~ to t ~ br d Oxrdnrior~ Nurtlber concept of Oxidation concept of Reduction

--

1

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Methodology

11.

KEME1)IAI. TEACHING MATERIALS IN CHEMISTRY

The lnvestigator prepared Remedial Teaching Materials for

the follow~ng topics in Chemistry for Educationally Backward students studying in Standard IX

(i) (ii) (iii)

Periodic Table .4tontic Structure Oxidatior~ Reductior~ &

For the preparation of Remedial Teaching Materials, the Investigator made a detailed analysis of the content and literature related to the selected areas and identified learning points (LP)

-

Periotlic

Table

(LP=16),

Atomic

Structure

(LP=ll)

and

0.uidutiorr & Reduction (LP=9).

Each Learning point is explained with suitable learning situat~ons, Charts, Pictures, Models. Experiments, Discussion. Projects, Concrete situations, Problems and Outdoor activities.

Provision for developing scientific skills and social skills were given due importance while preparing the Remedial Teaching Mater~als.

The

Remedial

Teaching

Materials

(prepared

by

the

Investigator) on the topics Periodic Table and Atomic Structure are given below: [Note: The Investigator prepared 3 Remedial Teaching Materials on the topics, Periodic Table, Atomic Structure and Oxidation & Reduction. But Remedial Teaching Materials on two topics viz.,

Periodic Table and Atomic Structure

108-3,441

, are given below.(pp

SCHOOL OF PEDAGOGICAL SCIENCES MAHATMA GANDHI UNIVERSITY

KOTTAYAM

REMEDIAL TEACUING M A TERIALS

ON

PERIODIC TABLE

(STANDARD IX)

Prepared by

RAJESWARI. K

Supervised by

:

Dr. EXEMMAL. J

(Supervisirrg Teaclier) Reader Deparfmerrt of Educafiorr Urriversity of Kerala

CFENE(DI,U

C 7 5 N mRIAU HN; 3

Remedial Teaching Materials on the topic PERIODIC

TABLE is subdivided Into 16 Units. Details are given in

pages 108-254. In each Unit, students are provided chances

Tor observation, classification, identification, discussion,

analysis and concept formation.

Suitable charts, models, examples, illustrations, life situations are also used for developing new conceptslteaching points. Practice session is given at the end of each unit to

test

tile level of attainment of the students. and

Reference Section

Extended

Activities

are

given.

Achievement Test on Periodic Table is given at the end of

thc ~nater~al.

--

-~. ~~.

1.

CONTENTS

UNIT 1

HISTORY OF CLASSIFICATION OF ELEMENTS

UNIT 2 UNIT 3 UNIT 4

MENDELEEV'S PERIODIC TABLE MENDELEEV'S PERIODIC LAW MERITSANDDEMERITSOF MENDELEEV'S PERIODIC TABLE

UNIT 5 UNIT 6 UNIT 7 UNIT 8 UNIT 9 UNIT 10 UNIT 11 UNIT 12 UNIT 13

MODERN PERIODIC TABLE THE MODERN PERIODIC LAW PERIODIC TABLE CHEMIST'S MAP GROUPS - VERTICAL COLUMNS PERIODS - HORIZONTAL ROWS THE ALKALI METALS HALOGENS TRANSITION ELEMENTS GROUP NUMBER AND VALENCE ELECTRONS

-

UNIT 14

PERIOD NUMBER AND NUMBER OF SHELLS

UNIT 15 UNIT 16

ATOMIC SIZE DOWN A GROUP ATOMIC SIZE ACROSS A PERIOD

Methodology

(l

INTRODUCTION

\

1

i

fhe Periodic Table is a product of the

contr~butions chemists from many countries. It of has taken centuries of work to arrive at this

I

at rangement of elements.

(

Drnitri Mendeleev

1834- 1007) was a Russian chemist who drew up

table. He did this by clrarting the t i ~ s tP e r ~ o d ~ c

I

tire known cl~emical elements

I

order of

irlcreasirrg atornic weight, altlrough we krrow that

l

I

it is tlre order of atomic number tltat is

!

1

\igrrijicant. Tlrr Modern Periodic Table is an

1I errcyclopedia of all the krrowrt elernerrts. It also

I 1

provirfes space to accommodate elemerzts yet to be rlisrovered. Tlre periodic table is useful

1

because tlrere is regularity in tlre clzemical properties of tlre elements.

I

1

/

\

'I'he arrangement of elements in the periodic table is useful as it is possible to predict the properties of an individual element from its position. -l'he Modern Periodic table is a table of all the chemical elements, in order of their atomic numbers so that elements with similar properties

arc close to each other. The Modern Periodic

Table was desigtted by Hertry Moseley.

Merhodolow

1I

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)

~

]

~

~

....~

S. 1 I

No : Learning ~I o n iI Antome ~,avosie<-Dobereiner, Newland and Dmitri

1

!

-

I

(

lvanovich Mendeleev and Henry Moseley made several

1 attempts to classify elements

A

-

I

1

/-2

I

Mendeleev arrangd elements in the periodic table in the

Increasing

1 I

4

I

order of atomic masses

Mendeleev's periodic law states that physical and

I

I

chenl~cal properties of elements are periodic functions of thelr atomlc we~ght

--

1 1

1

,

I.

Mendeleev first time in the history. Mendeleev1 s periodic table does not precisely follow the order of atomic mass and some dissimilar elements were arranged in the same group

---

i

1

I

.t

I,.

(

I

5 , 7'he Modern penodic law states that the properties of

-

- - - -

1

/

0

cle~ncnts perlodic functions of their atomic number are

,

~

. ~..~

~

I

']'he Modem Periodic Table was designed by Henry Ihc eiements are arranged in the increasing order of their atomic number

I/ 1

I

11

I

~

11.

-

7

I

'

I I

i ~ i . 7'here are 1 8 groups and 7 periods

~

.-

Periodic table

miy

be defined

i

varlous elements according to their properties, in a tabular

T--7

~~

The vertical columns in the Periodic Table are called groups

II

There are 18 groups in the Modern Periodic Table

~

1

- . -

I

9

I

The horizontal rows in the Periodic Table are called periods There are 7 perlods The Group 1 elements in the periodic table are called alkall metals

I

II

- .

tI

1

I

(

10 I

+

I

I I

11

The Group I elements are Sodium, Potassium, Kubidlum, Caesium and Francium

. . .. .- - .

/

,

I

-

, I

The Group 17 elements in the periodic table are called halogens The Group 17 elements are Fluorine, Chlorine, Brom~ne, Iodine and Astatine

~.~~

I

I

I

-

11

+

!

he elements in groups 3-12 in the periodic table are called trans~tion elements..

1

1 3

4

1 Period Number represents the number of shells in an atom

~~~

I

t

I

In Group I and 2, the number of valence electrons is

I

1I

1

/

IS

16

equal to group number ~i I'rorn the group 13 to 18, number of valence electrons

IS

I

I

I

I I Atomlc s u e decreises from left to right in a period due to /

---

I ; Atomic size increases from top to bottom in a group due ( , to Increase in number of shells I

equal to group number minus 10

-~

1

I

Increase in the nuclear charge without increasing the number of shells.

. . .

- --

I

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--

Methodology

--

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PREVIOUS

. . .~

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St~rrlents encouraged to recall the followitlg concepts: rlre

I

Elements are pure substances made of the same atonls.

kind of

I

Elements exist in solids, liquids and gaseous states Compounds are pure substances made of different of atoms kind

-1

J

In an atom there are equal number of protons

and electrons

J

Atom~c number atom.

IS

equal to the number of protons

in an

-1

Elcctl-ons in shcll

an

atom

are

present

outside

the

and are arranged in shells

J

In an atom the outermost shell is called the valence shell 'l'hc eler:trons present in the outermost shell are called valence electrons

J

-

,\'i

z h a s e I1 I / ' Stu(1o111.s erzcouraged to write the answers for the following are

>

qlrestiotls

in

the space provided.(recalls different elements

prescJnt in the r~ature)

i

I

)

Two lighter elements

(i)

(ii)

( 2I

Two elements in the gaseous states

6) (ii)

( 3)

-1wo elements in the solid state

(i)

(ii)

(4I

'l'wo elements in the liquid state

(i) (ii)

(5)

l'wo elements present in the

(0

(ii)

atmospheric alr

(0)

I he elements in water

6)

(ii)

( 7)

'fhe elements in Carbon dioxide

(i) (ii)

~~

~

Methodology

(8)

T w o metallic elements

(i)

(ii)

(9)

'Two nonmetallic elements

(1) (ii)

(

I O)

Two elements having isotopes

(i) (ii)

(1 1)

Two elements used for making ornaments

(i) (ii)

( 12)

Two elements commonly used for (i) making house hold utensils (ii) Two elements used for making weapons (i) (ii) (i) (ii)

( 13)

( 14)

The most abundant element in the atmospheric air

(

I5 I

The most abundant element in the (i) earth's crust (ii)

An element used as thermometric (i) liquid (ii)

( 16)

( 17 )

Thc elements present in

(i) (ii) (i) (ii)

Common Salt

( 18)

Two coinage metals

I

NOW THINK

Make a list of other known elements (other than questiorz rrumbers 1 to 16' pp

'Ir-9 to you

Box [ I ]

Nitrogen, Phosphorus, Sodium, Potassium, Magnesium

I

Students are encouraged to identify that there are about 116

ele~r~ents

S~lrtlorrtsare errcourageci to fatniliarize the two illustratioizs

giljcvi

hclo~,

~.~ - .

< :

~~

~--. .

ILLUSTRATlON (I)

Co11.\11ier a

I~IUS~C shop.

Suppose Cds and tapes are placed in

gr.ozrps such as chart music, dance, melody, top hitz etc. This nlcikr.\

it

easier. to,find the kind of music looking for:

Fig. 4.1 Arrangement of Cassettes

Lcr I

s~z~derit~ cot~pcire such a nlusic shop with an

~~i~c~ltr.s.sifierl utie.

~

~

~~

Methodology

Lei t l l c ~ stu[letzts consider the arrangenlent of books in a library:

111

c,ertain libraries books are placed in groups such as

nor~cis, shol-t stories, journals, dramas' scientific books, hiogr-lr/~h rzuiobiographies, etc. ies,

Iri

cerfair~ other big libraries books are placed in groups Arith~i~tic, Botar~y, Chemistry, English Literature,

.SLIC./I

(1.5,

G'o~c,t.<rl Kncl~~ledge, Etzgineering, electronics, periodicals , ctc. ,2,f(rkesrile students aware of the advantage of such an rrrt.rlt~gc~~~ctzt cfbooks. Putting books into groups in this way is calleti cltrssiji~itzg

Fig. 4.2 Arrangement of books in a library

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~-

~

~p~

~

119

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Methodology

Through the above illustrations students find out the conkcnlence of classification and also encourages to think about the advantage of classification in Chemistry.

Box [2]

'

I

Advantage of classification of elements

Made the study of elements easy

a

'

d

THINK AND DISCUSS

F'rol~irlc oppor.turlity for. classiJLing the substances given in

BOX1.31. 1t1 rlifjer-ent wuys.

Box [3]

/ '

I

/

'

\

Oxygen. water, Carbon dioxide, Hydrogen, Sulphur, Nitrogen, Potassium hydroxide, ammonia, Aluminum, Nitric acid, Sodium hydroxide, lodine, Zinc, Ferric Sulphate, Gold, Carbon, Potassium, Ferric Sulphate.

\

I

-

-. .

Methodology

P~.o\,iri~ttg opportuniv to classify the above list of substances into tllc Jollowitzg c,utegories:

1

Solld, 11qu1d gas and

2 Elements and compounds

3

Metals and nonmetals

4 Aclds and bases

( 'lnssijj~i/lg e1ement.s

(Box 3) into solid, liquid and gas.

-

-

Sulphur Alitrniniurn

~ ~

Water

Nitric Acid

Oxygen Carbon Dioxide Nitrogen

~~~.

I

St~rrlc,/lts( l i . ~ ' etirouraged to expand each group 191 adding I'i.o\.ltli/lg oppor-tutzitj~ to recall the dgferent mode:, c,lo.\ \c/ic.rrtiotl /nude bj, tliepupils:

S u b s t a n c e s c a n be classified i n different ways

of

-

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--

-

-

-

Methodology

Students are ericouraged to record the action of Sodium, Potassiutil, Iron and Copper with water (in the space

~p~~

SI. 1~ !

-

-

No.

. . . . .. .

~ ,

!

Experiment

.. .. . .

Observation

Inference

Vigorous reaction Putting sodium in water

1

ACTIVE METAL

.. . . .

/.. -

. .

- -.

i

2

.

1

I

I

Putting potassium in water

-

Vigorous reaction

' I .

I ,

ACTIVE METAL

-

1

3

I

1

/

!

Putting lron in water

.

No change

INACTIVE METAL

.

I

4

Putting copper in water

No change

:

INACTIVE

I

METAL

--

Encourrrgl~lg .studerlts to classlfy elements(Sodium, Potassium, /rot1 (111d Copper) on the basis of their hardness.

~~ ~

r:-';.! rri

-

- -- . -.

--

Methodology

Experiment

1

Cutting sodium metal with a knife Cutting a piece of knife

can be cut easily

SOFT METAL

. .

-

1

-~~

j can be cut 1 som METAL

1

.

+

col7per C'utt~nga prece of I Iron

Cannot be cut easily

HARD METAL

identities the advantages of classification of elements:

/'

Classification of elements made the study of elements easy and more convenient

,' ,

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.

-

.

Methodology

I\

.

\ , < \ /

LET US THINK AND DISCUSS

Y--'~ \

1

UNIT 1

HISTORY OF CLASSIFICATION OF ELEMENTS

Learning Point

Antoine I,avosier, Dobereiner, Newlands, Dmitri lvanovich

Mendeleev and Henry Moseley

made several attempts to classify

clemei~ts

~

~

~

~~

I / '

I'r.ovirlirig oppot.tunity to acquire irfol-mrrtion of .sc~ic~rztrst.r thejieli ofclasslfiing elernerzts it1 /,'nr~lilicz/-isirrg i~?lportant tlie cltemists and their c,or~trihutiorrs clussijjing elenzerzts: in

-

--

-

-

Methodology

The work done by Lavosier(1789)

-

-

-

-

Lavosier marked the beginning of classification in 1789. classified the then He known

elements into METALS and

NON METALS

1

Fig. 4.3 Larosier

I

1 CLASS I

IFICA

-

1

TION

('I.AVOSIBK

--

) = c > --'

OF

METALS

1

CNTS

1

--

.

-

-

-

-

Methodology

Si111i('rlts (ire etlcout.ngeCf to go through the contributions of

Dobereitlev (181 7)

Dobereiner:

( I ) ldentified the triads (group oftlzree sinzilar elements).

(i)

Litl~iurn, .%ciium, lJotnssiur~z

Fig. 4.4 Dobereiner

I

(

( 2 ) Used atomic mass as the basis

for grouping elements.

1

-

-

-- . -- .

1 ) o b c r c i n c r ~ Identification of Traids

-

-

-

- -

Methodology

Discussing the contributions of IVewlands (1 864)

0 .

-

The English scientistNewlandsarranged the elements in the order of their increasing atomic mass. He argued that the properties of eighth element was repeated as the eight note in musical notes (sa, ri, ga, ma, pa, dha, ni, sa). Based on this observation Newland postu,lated

~ i g4.5 Newlands .

the

Law

of

Octaves(simi1~zri between e v e y eighth element like the

eig/rt/~ note oj'nn octave in rnu:;ic). Newlands

was

the first to use numbers in a serial order and to predict periodicity.

Newla~~ds c

d L,aw of Octaves

2

DESCRIBING THE MAJOR CONTRIBUTIONS OF

Fig. 4.6 Mendeleev

I'ROC'ELIURE

ADOPTED

BY

MENDELEEV

FOR

CLASSIFY 1NG ELEMENTS More than 60 elements known at the time was

He wrote the atomic mass and properties of elements on separate cards.

He made a comparative study,

i i

Published :I table,

And Classified the known elements.

a a a

-

--

--

-

-

-

Methodology

Classification of elements by Mendt:leev Mendeleev's periodic table

PBBIODIC BYSTEM OF TEE ELEUESTS IN GROUP0 AXD EEBI&&

j

1

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0

, , ,

1 I

n z ,

-...

--

. .

ORDUPE

or L L t Y E r n

........

,

11

i

! v n ....VII .................... . .

1x7

,

, ,

I

..-

.

VIIX

-

i

:

- - H i

-

I

-i

-

'1

-.

'

-,

-

t

.

I

.....

Rat& W

N. L.

Dnoa

C,

'8x0 1 118

181.9

1"

137-4

U.

.Ih~oool rlum

l s l . . . ., l

i ~ aoe

j

, -

! 18U

140

-

-

---

PT-I

*

I

I'cl.~odlc '1 able

Metkodolom

Sti~derrtsare encouraged to develop concept about Mendeleev's Periodic Table(throug11observation, discussion and questioning)

( I ) What is the basis of classification

of Mendeleev's

periodic table?

(2) Whether the elements are arranged in the ascending or

descending order of mass numbers?

(3) How many rows are there in the table?

(4) How many columns are there in the table? (5) How many elements are included in the table?

i

C'ONCEPTS OF MENDELEE V

(1) Numbered the elements according to

lie atomic mass(mass number) (2) Arranged in the ascending order (increasing order) of atomic mass

(3) There are Six rows

(4) There are Eight columns

(5) Sixty elements are included in the

\

\\-.

table

-

--

Methodology

DISCUSSING

THE CONTRIBUTIONS OF HENRY

MOSELEY

I

-

Fig. 4.7 Henry Moseley

Henry Moseley, an English scientist proved

that it is the number of protons, ie. the atomic

number, that can be called the identity card of an element. Moseley designed the Modern

Periodic 'Fable.

-

- -. - --

Methodology

llobereiner was the first to identify the triads Iloberneiner was the first to use the atomic mass as the basis for grouping. Law of octaves .was formulated

by

Newlands Mendeleev first listed the known elements

in an ascending order of their atomic mass

Moseley developed the Modern Periodic 'I'able

,, ,

/'

,.-

_ -

Scientific Terms / Concepts

LAW OF OCTAVES

x, .

TRIADS

-. . . ~~ ~ . .

)

i

--

-

- -

Methodology

QG

CONCLUSION

Lavosier, Dobereiner, Newlands,

Mendeleev and Henry Moseley made several attempts to classify elements

.-

, T-------

EVALUATION

Fill

(I )

blanks. Choose the correct answer from tile hriickcts

irl rile

Law of octaves was formulated by --------(Mendeleev, Newlands, Dobereiner) (Mendeleev, Newlands, Ilobereiner)

1

-----

[ ( 2 ) The triads were first identified by --------

1 ( 3 ) -------lirst listed the known elements in the order

of their atomic mass (Mendeleev, Newlands, Ilobereiner)

Ii ( 4 )

I

Modern Periodic 'Table was developed by (Mendeleev, Moseley, Dobereiner)

1 ( 5 ) What is the basis of classification of I Mendeleev's Periodic Table?

( 6 ) Give an example for a Triad?

I

-

-

. .

-

-

Methodology

- --

UNIT 2

--

-

MENDELEYEVX PERIODIC TABLE

earnin in^ Point

Mendeleev arranged elements

in the periodic table in the

increasing order of atomic masses.

I'uplls have learnt that different elements show different propert~es. The) have also learnt that Elements are

classified on the basis of atomic masses

DEVELOPING 'TI-IE CONCEPT OF PERlODIC TABLE

1:ncourage pupils to go through the Mendeleev's Periodic

Table (PT-I ) and provide opportunity to find out what is a period and what is a group..

Methodolow

Let tlrc~ studet~ts tllrough the Mendeleev's Periodic Table: go

(PT I)

to

Ei~c,orii.clgr the students

arzsMier the following questions

oh.\ rt.Isltlgt l ~ Mendeleev ' Periodic Table. r s

I . How many columns are there in the table?

2. Hoe many rows are there in the table?

-----------------------------------

3. What is the basis of classification?

I<~icourages ldent~fy to Group and Period

------------------

I'ro\idc opportunity to locate and find out the periods and groups

I

1I--~

,>

I

I;.

Periods are Horizontal Rows

j

-

1

G

G r o u p s are Vertical C o l u m n s

Methodology -

111 r l ~ c

Mmdeleev's Periodic Table elements

1

ar-c arranged in t h e increasing order of atomic

masses

I'lle horizontal rows in the periodic table are c;~llccl groups

-

'l'he vertical columns in the periodic table are callcd periods

__-/

-

-

, -

i

\

Scientific Terms / Concepts

RIENDELEEV'S PERIODIC 'TABLE

..

--

----

Mendeleev arranged elements in the periodic table in the increasing order of atomic masses

-

-

(

;

EVALUATION

..lri.s\z~rr- ji,llo~vitzg questions: rhc

i.

f i l l in the blanks:

a.

!

l~iorizontal rows in the periodic table ar called ---------

b. Vertical columns in the periodic tab1

!

I

I

are called ------2

LL hat

IS

the basis of classification of

I

blendeleev's Per-lod~c table?

. -

_ I

-

-

. -

-

--

Methodology

-

UNIT 3

-

-

MENDELEYEV'S PERIODIC LAW

Nlendeleev's periodic law

states that the properties of

l'~inctions of masses

t h e ~ r atomic

I

. ~

~

-

p~

-

. -.

> . .

PREVIOUS KNOWLEDGE

~~~ ~ ~ ~ ~

7 , '

~~l~ilrirew discuss tlze special features of Mendeleev's

>

1.c.r

illt,

Periodic Table

L>~.\c,rrc.>~ng c~lzaracter.istics Mendeleev 's periodic table: ille of Stlrtlcvlt\

1111rll 1110

czt.c.

encouraged f answer the following questions o

help of Mendeleev's Periodic Table (PT - I)

.

~

~

Methodology

I . I lo\\ many elements are their in the table?

2. I lo\\ niany groups are there in the table?

3. I lo\\ niany pcr~ods there in the table? are

...................

...................

...................

4. Whar 1s the basis of classification?

...................

5 . What 1s the order of arrangement of elements'? ...................

0 . As you proceed from left to right in a period,

\vliar changes do you notice in the atomic mass ol'ele~iients'!

7. li'licn Mendeleev arranged the elements in

...................

the order ol' increasing atomic mass, did the c l e ~ ~ l c ~ l t s similar properties fall on \vitIi

;I

sroup or i n a period'?

...................

I'~.o\.rdt.opportunity to recall the seasons of India and tlreir oc~c.za-rc~trce a periodic ??.tanner(understanding itz tlre ir~err~~~rrg of per-iodicityl

Stlrrier~~s [email protected]' periodic roperti ties of elements by tlze oh.sc~~.~~trtiorrdisc~rssion. ulld

-

--

- . -

Methodology

Provrtl~tlgopportunities to arrive at the Mendeleev's Periodic

Law (through discussion and observation of Periodic Table)

Mendeleev's Periodic Law

THE PROPERTIES OF ELEMENTS ARE

PERIODIC FUNCTIONS OF THEIR ATOMIC MASSES

----

-

--

-

In the Mendeleev's Periodic Table, the properties of elements are arranged the properties

of

elements

are

periodic

functions of their atomic masses.

1 1 I

I

The

Mendeleev's

periodic

law

i

states that the Properties of elements are periodic functions of their atomic masses

I I

I

--:

i

i

I

1

,-?

.~II.\

EVALUATION

uret-f/refo//o lr,rtlg questions:

State Mendeleev's periodic law

I

i

( 1)

:

( 2 1 What is the significance of Mendeleev's periodic table in the classification?

( 3 ) l l o u many periods are there in the

I I

i

klendeleev's periodrc table'?

( 4 Ilou many group!; are there in the

j

i I

Mendeleev's periodic table?

( 5 ) What

i

-

are

the

characteristics

of

I

hlendeleeu's per~odic table?

----

_ I

-

. -

-

Methodology

UNIT 4

MERITS AND DEMERITS OF MENDELEEV'S PERIODIC TABLE

.--

---

Learning Points

(i) blendeleev

exhaustively

classilied the elements for the

first tlme in the history.

( i i ) Mendeleev' s periodic table

does not precisely follow the o~-dcr l atomic mass. o

(III )

home

dissimilar

elements

\<ere arranged in the same

groLll1.

~-

~

PREVIOUS \<NOWLEDGE

~

\tutlcnt\ ha\e learnt about Mendeleev's Periodic Table and

I'criodic 1,aw ( U n ~ t s to 3) 1

Methodology

Di.sc,~r.\.\ the clzuructeristic feutures of the Merzdeleev's I ng Periodic Table (,Ttuderzts (we encouraged to find the answer

, f i illc follovr,uzg qirestiorls based on tables :pp ........) ~

(1)

Is the increasing order of atomic masses of elements strictly

adhered to':'

(2) Are elements with different properties included in the same group?

( 3 ) Wilat 1s the action of Potassium with water?

(4) \+'hat 1s the action of Copper wit.h water?

( 5 ) U'liat about the hardness of Potassium and Copper'!

(0) ('an I'otassluni and Copper be included in the same group?

ANS\\'I.:K KEY

J

-

0

- -

(

1 ) I)oes not precisely follovv the order of atomic Inass

( 2 ) Elenlents with different properties are included in the same group (eg:- Potassium

1

21nd Copper)

(3)

I'otnssium reacts vigorously with water (:opper is passive towards water

1

1

-

I

(4)

I

( 5 I'otassium is soft while Copper is hard

(0)I'otassium and Copper cannot be included in the same group

-

I

. .

144

- . .. .

Methodology

Students are encouraged to develop concepts about the me& and deme~?S of Meodeleek 5 Per/od/c Table (through observation, discussion and questioning)

Ident~iylng major merits and dei'ects of Mendeleev's Periodic the

Table

r~ 1 I

~

--

MERITS

-

-

T

i

I<xhaust~veiy classified the Does not precisely follow the

t

clenients lor the first time

-

! order of atomic mass

arranged in the same group

1

T o m i dissimilar elements are

I

I

-

-

--

Mcndelecv arranged t h e non elements in a t a b ~ ~ l form ar

* M e i ~ d e l e e v exhaustively

classified

the

clcments for the first time in the history.

I

/I

Mcndclcev's

periodic

table

does

not

precisely follow the order of atomic mass.

Some dissimilar elements were arranged in

the same group (e.g., K, Cu )

- -- -

145

. -

-

-

-

Methodology

(1 )

Mendeleev exhaustively classified the elements for the first time in the history. (2) Mendeleev's periodic table does not precisely follow then order of atomic mass. (3) Some dissimilar elements were arranged in the same group.

EVALUATION

1 A r i s ~ i vihefullowing questions ~.

I

i ?

major demerits of

I

I

1

I

( I ) Write the merits of' Mendeleev's periodic

table

(2) What

1

are

the

1

Mendeleev's

periodic table?

- -.

-

-

-

-

-

Methodology

UNIT 5

MODERN PERIODIC TABLE

- -

-

Learning points

(i)

'l'he Modem Periodic Table was designed by Moseley. Henry

( i i ) I'he elements are arranged

i n the increasing order of'

their atornic number.

(11 I )

l here are 1 8 groups and 7

per~ods In I'er~od~c I'able

the

Modeni

-

. -

---

J ,

PREVIOUS KNOWLEDGE

- - / - I

>

I'rovitiitlg opportutlity to recall the concept of Period

~ t r t Group. i

1

1 lor~zontal rows are called periods.

J

Vertical columns are called groups.

~

-

~~~

~~~

~~

Methodology

1x1 /he studetlt.~discuss the special features of the Modern Pel-iotlic fablr

Disc~~r.s.slng the characteristic properties

of the Modern

Perlotllc Table (wit11the help of Periodic Table).

Modern Periodic Table

i.\

-

-

- .- -

Methodology

Stuticv~ts rrlcouraged to write the answers for the questions rrre give11helow. (Observing PT-2)

(

I i llow many groups are there in the table?

................

( 2 ) How many periods are there in the table?

................

................

................

(3 ) Name the smallest period.

( 4 ) Name the members of the first period. ( 5 ) ( i ~ v e atomic numbers of the first the

per~od elements.

( 0 ) Name the members of the second period.

................

................

( 7 ) Whether the elements are arranged in the

Increasing or decreasing order of the

atomic

number?

-

Methodology

Dcvelopl~lg cliagrat?zmatic representation of 8 MAZNgroups (, I

2, 13, 14, 15, 16, 17and 1) 8.

B 13 A1 31 Ga 49 In 81 TI

C 14 Si 32 Ge 50 Sn 82 Pb

N O F N e 15 16 17 18 P S CI Ar 33 34 35 36 As Se Br Kr 51 52 53 54 Sb Te I Xe 83 84 85 86 Bi Po At Rn

* **

Lanthanides (14 elements) Actinides

(14 elements)

ldcntifying

7

periods

in

the

Modern

Periodic

Table

(Observing PT -- 2)

-

~

. .

-~

Methodology

Providing opportunity for the pupils to locate groups 3 to 12

*

**

[,anthanides (14 elements) :\ctinides (14 elements)

Elzcoilt-age the students to develop the concept about the u~.r-cltrgernzerzt of elements in the Periodic Table- CI

( / I Z I . O ~ ~ oh~ervution discussion) ~/I and

Elements are arranged in the increasing order of atomic numbers.

--

-

-

-

Methodology

Stutlrrlts are erzcouraged to answer the following questions

(hn.sc~ti the Modern Periodic Table.) or1

What is the basis of classification? How many horizontal rows are there? How many vertical columns are there? Where is the place of transition elements? How many rows are there below the main block? Name the incomplete period? Name the shortest period:?

How many elements are there in the shortest period?

How many elements are there in the second period?

tlow many elements are there in the third period?

Ilow many elements are there in the fourth period? How many elements are there in the fifth period? How many elements are there in the sixth period? Name the elements in the first period ? Name the first element in the second group? Name the first element in the fifteenth group? Name the first element in the seventeenth group?

How many members are there in the eighteenth group?

Name the first element in the last period?

Methodology

ANSWER KEY

0

I

2

-

I1

4

~

~

~

-

Increasing order of atomic number

,7 horizontal rows

3

4

1

1 18 vertical columns

~

~ p~ ~ ~ ~ p ~ ~ ~

Between groups 2 and 1

~~

~

--

I't.o~~itlit~g ~ p o r t u n i ~ ~ d e n t l . the Number of' Groups and oy to I

P~riorls Tlze Modern Periodic Table in

\

PERIODS = 7

\-/

Encour-clging studer~tsto recall the name of the scientist who

developed the Modern Periodic Table

--

Henry Moseley (Figure 4.7), an English scientist

proved that it is the number of protons, i.e., the atomic

number, that can be called the identity card of

an element.

- -

In the Modern Periodic Table, there are 18 groups

There are 7 periods in the Modern Periodic Table Henry Moseley designed the Modern Periodic Table Elements are arranged in the increasing order of atomic number in the Modern Periodic Table

-

-

Methodology

CONCLUSION

(1) The Modern Periodic Table was

I

designed by Henry Moseley (2) The elements are arranged in the increasing order of their atomic number in the modern Periodic Table (3) There are 18 groups and 7 periods.

I

EVALUATION

( A~isivcrthefollowirzg questions:

I . How many periods are there in the Modem Periodic Table?

I

2. How many groups are there in the Modem Periodic Table?

1

i

3. Who designed the Modem Periodic 18blez?

4. What is the basis of classification of

Modem Periodic Table?

-~

~

~

..

-

Methodology

UNIT 6

-

THE MODERN PERIODIC LAW

--

-

Learning Point

'l'he Modern periodic law states that the properties of

I1

-

lilnctions of' their atomic number.

I

I

~~

PREVIOUS KNOWLEDGE

.

~~

Students have learnt about MENIIELEEV'S PERIODIC

I At3l.t: (llnit 2 and 3)

/'i.o~,itio~g o/~poi.tzuzit~~ to I-ecalltlze following concepts

C ~ ~ O L I Pare vertical columns in the periodic table S

J

Per~ods horizontal rows in the periodic table are

-

-

-

- -

Methodology

Sttctle/lt.c (Ire etlcouraged to develop the following concepts tllr.o~c,ylrohservc~tion,discussion and questioning: (Providing oppo/.iu/~lty observe the Modern Periodic Table - PT - 2 ) to (G'i\:utg czrzswer-s to thefollowing questions)

( 1 ) How many groups a r e there in the Modern

Periodic table?

(2) How many periods a r e there in the Modern

periodic table? (3) Which is the incomplete period?

(4) Which is the shortest period?

(1)There are 18 groups in the periodic table

(2) There are 8 periods in the Periodic table

I I' I

~

(3) The eighth period is an incomplete period

'(4)

I

First period is the shortest period

,--

tile Oasis~ of clrrssifkation of Modern Periodic Table I tl~~.ot{gh obs~rv~~tzon, discussion and based on the structural ~.c/~/.e\rllfatrolz the Modern Periodic Table (PT-2 & PT-3). qf

I

-.

--

. -

Methodology

-

. --

Methodology

-

Provldirlg opportunities to go through the periodic tables:

(I'T -2-. 3), -& Identifiing the symbol and rztomic numbers The first element in the periodic table and its atomic number?

I

-

-

The second element in the periodic table and its atomic number?

I

/HELIUM]

I I .

~

1Le third element in the p

e

r

i

o

d

i

c

~

l

atomic number?

(

'I'he tburth element in the periodic table and its atomic number?

I

1 BERYLLIUM 1

. .

.-

Methodology

Namc the third element and what is its atomic number?

Sflrdctr~.\ errcouraged to find out the number of periods in the (Ire Periortrc. 7crhle

1

- - -~

7 PERIODS

1

Reason

4HORIZ","J

.

I

Stictlc~rirs rrrr ericouraged to find out the number of groups in

tlir I'ct-rodic Table.

..,

1

~

-

I 8 GROUPS

~

] Reason

1-4

COLUMNS

Errc.orrt.c~g~~ .~tzrclet~ts ident~jj the order of arrarzgement of to c~Ic~~rrorr~.\t ~ rrr t l Ptv.iotiic 'lilbie(increasingorder of atomic number).

Lct the students represent the elements in:

I'ERIOI)

---I

. . -

Atomic Number-

---

-

-

-

Methodology

@ @ @@@@

Number elements

7

.

-

-.

p -- s e I ? 9 ha

1,

t Nuniber

i

--

--

a8

@ @

0a

/ -

-' KEY POINT

,' / ,

\

\

The elements in the Modern Periodic Table are arranged in the increasing order of atomic numbers

=+

\ .-\ /

--

-

--

-

.

.

Methodology

Provrtle opporrunity to compare the Modern Periodic table wit11Mendeleev's Periodic Table:

Students are encouraged to answer the following questions:

I.

WIIAI'

IS THE BASIS OF C1,ASSIFICATION OF

IN

ELEMENTS TABLE'?

THE

MENDELEEV'S

PERIODIC

2.

WHA'I' IS THE BASIS OF CLASSIFICATION OF I:I,EMENI'S IN THE MODERN PERIODIC TABLE?

Stutic~~~ts identijj the periodic properties of elements by ohsc~i.l,t~tion discussion. and

A~.~-ii<ing the Modern Periodic Law by observation and at tlisc,ll.s.sion.

,

/

'

i r

Modern Periodic Law

atomic number

k u

\

'\

states that the properties of elements are periodic functions of their

1

\.

-

.-

-

Methodology

-

'me elements are arranged in the increasing order of their atomic number There are 18 groups in the modern periodic table There are 7 periods in the modem periodic table

/--

Scientific Terms / Concepts

MODERN PERIODIC LAW

'. .. .

\-.--

@ CONCLUSION ?

1 1 / I

Modem Periodic Law states that the properties

are functions of their atomic number

of elements

periodic

I I

-

.

--

--

Methodology

j

i I

1

I

-

EVALUATION

Answer the following question:

(1) flow many periods are there in the modem periodic table?

(2) How many groups are there in the modem

periodic table?

(3) Who designed the modem periodic table?

(4) What is the basis of classification in the

modem periodic table?

UNIT 7 PERIODIC TABLE - CHEMIST'S MAP

---

Learning Point

I'eriod~c table may be defined as the arrangement of to various their

elements

according

piopert~es, a tabular form in

~

~

~

PREVIOUS [<NOWLEDGE

~

I:>

f'rov~diwgopportunity to recall the following facts:

J

Mendeleev arranged elements in a table.

I'lie horizontal rows in the periodic table are called

periods.

a The vertical columns in the periodic table are called

groups.

u

In Mendeleev's Periodic Table, elements are arranged

in the increasing order of atomic mass.

u

In Modem Per~odic Table, elements are arranged in the

~ncreasing order of atomic number.

-

--

-

-

-

Methodology

Stutlents ure encouraged to recall the concepts (C2and C3).

Classifcation of elements in to groups made the study of elements easy.

I '

Arrangement of elements irt rows and columns are based on the properties of elemettts.

E11c.olrrclget l ~ e students to answer the following questions with the hrlp qf'Mendeleev's Periodic Table(PT-I),.

I. I low many groups are there?

2.

Iiow many periods are there?

3.

4.

\Vhat is the basis of classification?

you proceed from left to right

As

in a period, what changes do you

~iotice the atomic mass of elements? in

-. .

-

-

-

-

Methodology

Modern Periodic Table

St~rdetrtsare ericouraged to answer the following questions with the lielp o Modern Periodic Table,. f

I.

2.

3.

4.

How many groups are there? blow many periods are there? What is the basis of classification?

As you proceed from left to right

i n a period, what changes do you

notice in the atomic mass of elements?

-

Methodology

~

Discirssitlg

Mrrgne.slw?l,

tlw position

of Sodium, Potassium, Iron,

Oxygen, Nitrogen, Gold, Silver, Aluminium,

Clilorine and C,'opper itz the periodic table

1 1

In the Periodic table, the elements are

arranged according to their properties

I I

~t

CONCLUSION

Periodic table is the arrangement

1

of various elements according to their properties in a tabular form

EVALUATION

---

Arlswer thefollowing questions:

I

/

1. What do you mean by periodic table?

2. What is the use of periodic table?

I

I

-

-

-

Methodology

UNIT 8 GROUPS VERTICAL COLUMNS

-

--

-

-

-

Learning Points

(I)

The vertical columns in the periodic table are called

I

-

( ~ i )There are 18 groups in the

Modern periodic table

I

PREVIOUS KNO

.-

L)iscussing tlze clzuructeristics of MODERN PERIODIC

72 BLf:'.

(fJro~:icling opportunity to recall that there are vertical

columrts in tlie periodic table)

Studerzt.s ure eizcouraged to go through the Modern

periodic table (PT-2) and to find out the number of groups

irr IIILJ periodic table

-

.

Methodology

Irientqying the name of each group

.

----

GROUP

-..

NAME OF THE GROUP

Alkali metal

1

2

. -

Alkaline earth metal Transition elements

-- - -

15

Nitrogen Family

16

-

-

17

18

~ ~

--

1 Noble gases

Halogens

I

/

I '

Develops the fact that Groups are

/

/-"

//

Scientific Terms / Concepts

k*

' 1

GROUP

\------

. .

. -

-

-

Methodology

Attention

Vertical columns in the periodic table are called GROUPS There are 18 groups in the Modern periodic table Groups are also termed as FAMILIES

Q

CONCLUSION

(1) The vertical columns in the periodic

table are called groups (2) There are 18 groups in the modern Periodic Table

'LA'

aI

I

EVALUATION

:

/ Ar,swer thefollowing queslions

I . Define group

7

I

2. How many groups are there in the Modem

Periodic table?

3. Name the following groups:

a. Group 1

UNIT 9

--

PERIODS HORIZONTAL R O W S

---

-

/ '

Learning Points

( i ) The horizontal rows in the periodic table are called periods

I

( i i ) There are 7 such periods

I

PREVIOUS - - -KNOWLEDGE

---Y

J

Recalling the characteristics of MODERN PERIODIC rABL E (PT - 2 )( Refer Unit 5 )

u

Providing opportunity to recall that there are 7 horizontal rows in the Periodic table

Stur1er~t.s Lire erzcouruged to go through the MODERN

PEHIOLl/C' T,iBf,E and to find out the rtuntber of PERIODS in

rlle 1'er.rodrc k b l e (PT-2)

-

.

--

-

.

Methodology

Encovrrrge studerzts to prepare a table representing the rzurrihel- of elerrtents in each period with the help of Modern Pel-iotiicx Table (PT-2)

Period

~~

No. of elements 2

-.

1

~

2

~~ ~

8

~ ~ p ~

.- . -.

~

~

3

-. ...~

8

18

~

4

--~ ~

5

.

6

~

--

7

.- ~~

INCOMPLETE

L)evclo/~itzgthe concept

(C4) about the number of periods in the

/--

There are seven periods in the Modern Periodic Table

-.

-

-

----

Methodology

1 DO YOU REMEMBER I

r

How many periods are there in the modern periodic table?

r Name the shortest period?

> >

How many members are there in the shortest period? t~lowmany members are there in the second period? Name the incomplete period Which is the longest period?

How is Group 6 and Group 7 differ from other

>

r

r

periods`?

r

Name the first element in the third group?

i Name the last element

T

in the fourth group?

Name the group to which the first member of each period belongs to

r

Name the group to which the last member of each group belongs to?

-~

~

~

Methodology

Lanthanides and Actinides

Stutlei~tsure provlded opportunity to find out tlze position of

laritltariides and actinides in the periodic table

Developing the layout of Modem Periodic Table and helps to

identify the position of Lanthanides and Actinides

LAN rHANlDES ACTINIDES

1 1 1 1 1 1 1 1 1 1 I I

Fig. 4.8 Lay out of Modern Periodic Table

Loctrrlng t l ~ rposition o f Lanthanides and Actinides in the Perrodrc Table( wit11 the help of PT-2 & Figure-23)

, ,

Lanthanides Actinides

\

PERIOD 15

PERIOD 7

-. .

-

-

-

Methodology

Developing t l ~ e concept (C5)about Lanthanides and Actinides

\

\-

Lantltanides and Actinides are placed as separate rows under the periodic table

The horizontal rows in the Periodic table are called Period There are 7 periods in the Modern Periodic table Lanthanides belong to sixth period Actinides belong to seventh period Lanthanides and Actinides are placed at the bottom of the main block in the periodic table

_ ' ,

/

//

/'

Scientific Terms / Concepts

PERIOD

\

,

L. 1 '

LANTHANIDES ACTINIDES

1 -

. -

-

-

-

-

Methodology

7-

1

!

(1) The horizontal rows in the Periodic table are called Period (2) There are 7 periods in the Modem Periodic Table

I

Answer the following

I

questions

1I

I

( 1 ) Define a period?

1

1

(2) How many periods are the in the Modem Periodic Table?

( 3 ) Say

1

whether

the

Lanthanides

and

Actinides constitute discrete periods?

. -

-

Methodology

UNIT 10 THE ALKALI METALS

Learning Points

(I)

The Group I elements in the periodic table are called alkali metals are Sodium, Potassium,

( i ~ They )

Rubidium, Caesium and Francium and are active metals

DISC LlSSlNG Tt1E CHARACTERS OF A GROUP

I'rovltie opportunity to go through thefirst group in the Modern Periodic Table

.~

3 1 1,i Lithium , II Na 1 Sodium ~

+GROUP I :

THE ALKALI METALS

,

I

19

!

I

ti

1

Potassiu~n jl-I<b :/ Kubedium

5s

(s '

.~

Caesium

87

Fr Francium

---.

--

-

Methodology

Studeizts uve asked to make display cards slzowirzg the atomic number and symbols

of

alkali metals.

Students carrying the

display cards showing the atomic number and symbols of Alkali Metals are asked to .face the whole class. Students in the class write down the members of Alkali Metal.

Provlditlg opportunity to compare properties of elements of

First Group.

Encouraging students to conduct the following experiments.

-

--

Nu

/

.. .

Experiment

a Cutting Sodium with a knife

Observation Inference Can be cut easily Soft Soft Reactive Reactive Reactive Reactive React violently React violently

1

-

~

b Cutting Potassium with Can be cut easily a knife

a Treating Sodium with ater 1 bP~reating Potassium with water

..

Vigorous reaction Vigorous reaction Burns vigorously

t a - i u r n i n g Lithium in air

3

. .

~

Burns vigorously ..~. Produces a Reacting Sodium with I White C: hlorine gas i powder .. . 1-bkeacting ~ o t a k i u m with Produces White Chlorine gas powder I-bBurning Sodium in air

~

1

Developng the co/zcepts C6and C7about Alkali metals (with tlie //rip of' experinlent, observation and inference)

Proviile opportunity to recall the formulae of some compounds of Soctiir~i~ Potassium and identify the similarities between the and for~nuluo f the cori~pounds Sodium and Potassium of

SI. No

Compound s of sodium

Formula

Compounds of potassium

Formula

I

Chloride

2

Chloride Na20 Potassium Oxide Kz0

/ Sodium

I Oxide

I

3

I

sodium Carbonate

N ~ ~ C Potassium O ~ Carbonate

NaN03 Potassium Nitrate

1

K~CO~

KNo3

1

--

Sodium Nitrate

-

-

-

-

-- .

Methodology

Striderrts are provided with pieces of Sodium, Potassium, Soriirrrn Choride, Potassium Chloride, Sodium Sulphate and Lithiurn Chloride. They are asked to place the above s~rbstartces by one in a Bunsen's Flame. orte

OBSERVATION

( 3

/-

---,

i Y'

-

Alkali Metals and their cornpounds give bright colours when placed in a Bunsen's Flame

L)et,elop~rzg

thc7

Concept (Cs) about the similarities in

properties oj'Alkuli tnetals

C8,) Alkali Metals show sintilor properties , -\-.~

-

-

-

-

Methodology

Provldr opportunity to identlh the mode of storing Sodium

and Potassium

POTASSIUM

Sodium and Potassium

,

METALS AND ARESTORED UNDER OIL

\ \ ' .

handled with

ldeni!fies tlze reactivity of Sodium and Potassium

U

Encolrruge students tofind out the reason for the Group I

elerrrerrts slrowirzg similar properties

Recc~llitlgthe concept of valence electrons and their role in a

Provide opportunity tofind out the electronic conjiguration of

alkali metals.

Element

Lithium Sodium Potassium Rubidium Caesium Franciurr~ Li Na

K

Rb

C: s

Fr

+ = d Identifvlwg the nunzber ofvalance electrons .,

-

n u

All Group 1 elements have one valence electron and

that is why they show similar properties

Developing the Concept (C9)about the nature of valance electrons in elements in the same group

Atoms of elements in the same group of tlie periodic table have the same number of valence electrons

-

.. -

--

Alkali Metals are Lithium, Sodium, Potassium, Kubedium, Caesium and Francium. They are soft and reactive metals They have only one valence electron. They a l show similar properties. l

/

I

1

I

/

Sctentific Terms / Concepts

ALKALI METALS LITHIUM SODIUM POTASSIUM RUBEDIUM CAESIUM

\

\

\

, ' ,

FRANCIUM

'\--

Methodology

-

(1) The Group I elements in the periodic table are called alkali metals. (2) Alkali metals are Sodium, Potassium, Rubidium, Caesium and Francium and are active metals

1

EVALUATION

1

Fill in the blanks:

( I ) First Group elements ~nthe Periodic

Table are called ----(2) Alkali Metals contain ---- valence electrons. (3) First element among the Alkali Metals is

11 Answer the following:

( I ) Name the Alkali Metals.

(2) Alkali Metals show similar properties. Why? (3) Sodium and Potassium are kept under Kerosine. Why?

-

.

-

-

-

Methodology

-- - - -

UNIT 1 1

~

~p~~

HALOGENS

/"-

Learning Points

(i)

F

table are called

'I'he Group 17 elements in the periodic halogens

( i i ) They are Fluorine, Chlorine,

Bromine, Iodine and Astatine and are reactive non-metals.

\

~-~~

PREVIOUS

/'r.ol:ide 0/7portunitj)to recall

J

l.luor~ne, Chlorine, Bromine and Iodine are non-metals. I'hey are d~atom~c molecules

J

11iscus.sing the Characters of a

Group

-

--

.

-

--

Methodology

Provide opportunity to go through the seventeenth group in the Modern Periodic Table

GKOUP 17

+

HALOGENS

Fluorine

ACTIVITY I

Students are asked to make display cards showing the symbol and atomic number of

Bromine

halogens (F, C1, Br, 1 and At).

Students

1 '

-

lodine

I

carrying the display cards showing the symbols and atomic numbers of halogens are asked to face the whole class. All

- -

1 students

in the class write down the

1 members of halogens.

Corrrl)irr.irzg the properties of elements of Seventeenth group

-

---

--

-

Methodology

E~lcoltr-c~ges identlfi the physical state of existence of to

tlalegons

Diagramatic representation of halogen atom

State of existence

...........

.. .

Bromine Br2

.................

LIQUID

~-

Iodine

12

a (30CO C (30 0 E 0

SOLID

Iderrtifjtirrg tlte common properties of halogens (Questioning and discrrssiorr and references)

I . Iiow many atoms are present in one molecule of Fluorine'?

......................

2. ('hlorine 1s a diatomic molecule. Why? ......................

3. Name the l~quid Halogen

4. What 1s the state of existence of

......................

t l u o r ~ n e Chlor~ne? and

-

-

--

-- -

.

Methodology

Idenfqying the similarities between the formula of the

conzpounds of Fluorine and Chlorine

- --potassium

-- - -- -

Sod~um Chlonde PotassiurnChlo~de

. -

Sodium Fluoride

---

1

KC1

( Potassium Fluofide I

1

mi

CaF2

HydrogenChloridr"C1 Calcium Chloride

. .- --. - .

~

1

j Hydrogen Fluoride j

CaCI2

I Calcium Fluoride I

I

Comparing the properties of Fluorine and Chlorine

Fluorine and Chlorine react with metals

- - .- - - . . .

Methodology

E,rplainitzg the reaction between Sodium and Fluorine

1 Sodium + Fluorine 3 Sodium Fluoride

2Na +

F2

3 2NaF

E.xpl(ur~ulg r-eactiori between Sodium and Clzlorine rile

( Sodium + Chloride 3

I

--

Sodium Chloride

L)e\$c~lor~rzg concept (Clo) about the nature of properties of the f71zro/.rrleatltl Chlorine based on F,, Fz, F3 and Reactions ( I )

(lt?f/ ( 2 )

/ -- -

Fluoririe and Chlorine show

Ellcournging to find out the reason for Group 17 elements

showing similar properties

Recnllirig the corlcept of valence electrons and their role

in cllemical reaction

A.

phase 1 9

-~

v

f'rovirie opportunity to find out the electronic configuration

/

number

-

1

I

Name Of Symbol the element

I

(

Electronic configuration

35

53

1 Iodine

Astatine

I

2, 8, 18, 1

85

At

u

I(ier~rifi~ing reason for showing similar properties by halogens .. the

All halogens have same number of valence electrons (7). So they show similar properties

- -. . .

Developing the Cbncept (CIJ about the nature of valence e1ectt.on.s in the atorns of elements in the same group.

,-'

Atoms of elements in the same group of the periodic table have the same number of valence electrons

Encouragzrzg students to go through the table given below, slrotr~rtlg t.eactlvity of halogens as we go down the group. the

Halogen

Conditions needed for reactions to occur

1

Reaction

Rromine

idin.

i i

1 1

Heating

Reaction Occurs

Strong Heating React very slowly

--

- -

--

Methodology

Developing the concept (C13 about the reactivity of halogens dowtl tlie group

The reactivity of halogens decreases as we go down the group (Example: Fluorine is the

first element and Iodine is the last element)

Identlfjing the most reactive halogen

..<-I-

7--- 1

\

--

' .

Fluorine is the most .. 'o~en

Atoms of the same group contain the same number of valence electrons Elements in the same group show similar chemical

-.

.

-

-

Methodology

171h group elements are halogens.

Halogens are reactive non-metals Halogens have seven valence electrons. Halogens show similar properties.

.- ---

/

//'

,/ Scientific Terms / Concepts

I

HALOGENS FLUORINE CHLORINE

.

BROMINE IODINE

Methodology

CONCLUSION

'The Group 17 elements in the periodic table are called halogens and they are Fluorine, Chlorine, Bromine, Iodine and Astatine

1

/ZI

(

I

EVALUATION

Fill in the blanks.

(1 ) Seventeenth Group elements in the Periodic Table are called ----( 2 ) Halogens contain ---- valence electrons.

1I

( 3 ) First element among the Halogen group is

1 ,411swerthefollowing: 1

( I ) Name the Halogens.

t 2)

1

I

j

I

Halogens show similar properties. Why?

A

(3) Name the most reactive non-metal.

--

-

.

Methodology

UNIT 12 TRANSITION ELEMENTS

-

--- -.

.

Learning Point 'l'he elements in groups 3-12 in the periodic table are called transition

elements.

-

-

~

~

~-

..~

PREVIOUS KNOWLEDGE

.

1'1~ovlde opportunizy to go through the figure 4.9 i.c~pi-esei~ting arratzgenlent of elements in group 3-12 the lu~.\cd 0 1 1 atottuc nur~lber..

n

-

.

21 22 23

~~~

l

26 44 75 76 108 27

45

24i25

28 46 78

29 47 79

30

48 80

~

,

-

39

~~ ~

40

41];2713 71

57

1

72

77

109

(Atoniic numbers from 21 are given in the columns)

Fig. 4.9 Arrangement of elernents in group 3-12 based on atomic number

-

--

-

-

Methodology

TRANSITION ELEMENTS

Periodic Table(PT-5)

Students are encouraged to answer the following questions with the help of' Figure-24 and PT-5.

I . I low many groups are there in the 'I ransit~on series? 2. Name the groups belonging to Transition series 3. Where is the position of Transition elements? 4. I low many 'Transition series are fhere in the Modem Periodic Table?

5 . Name some Transition elements

................

................ ................

................

................

-

-

-

-

- --

- -.

Methodology

Developing the facts Fd, Fs,F6 and F7

re are 10 groups in the Transition Series

(/;ransition

elements comprises of groups 3-12

I

ransi sit ion elements lie between group 2 and

group 13

(

F are 4 transition series There

Stutletzts are encouraged to identifi common transition elenlc~tlts wit11the help ofperiodic table (PT-5) and suggest the itn[~o~.ftrr~fc?ffurniliar metals. uses

I

Iron (making weapons), Mercury (thermometer), Gold (ornaments), Silver (ornaments), Tungsten

I

.

-

-

--

-

-

Methodology

E~~couruging answer the following questions to

1. Name five metals.

2. How many complete series are there in the transition

ser~es?

3. l low many members are there in the first transition

series'?

4. How many members are there in the second transition

series?

5. [low many members are there in the third transition

series?

6. Name the elements present in the tenth group.

7. Locate the position of Iron in the transition series.

8. Name the hmiliar elements from the first transition

series

9. Name the liquid metal.

De\selopirlg the Concept C13 about Transition elements

Trarzsition elements are metals

Transition elements are metals Elements belonging to groups 3-12 are called transition metals

,/ ,I/

__---

Scientific Terms / Concepts

\,I.

\--

-

TRANSITION ELEMENT

The elements in groups 3-12 in the

/I

periodic table are called transition elements

I

, i -

EVALUATION

11

I

Atlswer- the following. What are transition elements? ( 2 ) Name the liquid metal. ( 3 ) Name two metals used for making ornaments. (4) Name two transition metals used for rnaking electrical cables. (5 ) Name the transition metal used for making filament of lamps.

(

1)

-.--

-

--

-

-

Methodology

UNIT 13 GROUP NUMBER AND VALENCE ELECTRONS

-

-

-

- -- -

Learning Points

(i)

In Group 1 and 2, the number of valence electrons is equal to group number

( ~ i ) From the groups 13 to 18,

number of valence electrons is equal to group number minus 10

\

-

- -- .PREVIOUS KNOWLEDGE -.. -- .

- --

G

Students izmve learnt the electronic configuration.

1Vr-iting tlie electrorzic configuration of Group 1.

-.

-

-

-

Methodology

Efectrorric Corrfiguration of Croup I

--

-~~~

-

Electronic Configuration

.

~ ~~

-.-~,

No. of Valence electrons

1

1

tlydsogen

~

1

~-

I

-

~

~~

Sod~u~n

1

-

1 Rubedtum

~

2,8,18,8,1 2,8,18,18,8, 1 2,8,18,32,18,8, 1

1

('aest urn

1 1

. ~ .

~

L ) ~ ~ , , , i ~ p1i 1 1 g ) l c,o)lcept CI4about number of valence electrons ~

111

(;~.oi/p d e t ~ c ? ~ ~ t s I

c,,;

~ ~

'11 ~ r o iqeiemertts contairz 0.e

. ,,, valert ce electrort . .

. _

_

I'tiiting tile electrortic configuration of Croup 2

I

. . .

~

Element

... .

---

electrons

De~jc~lop c,orlc.e;r,t C I S /he ubout tzurnber of valence electrons in

AN Group 2 elements contairr two

,

valerzce electrorts

-- -

Methodology

CVritit~g electronic configuration of Group 13 tile

. -

- ---

i )

Electronic electrons

[LIement Boron

---

. .-

.

Alurnin~um

-

-

1

Ciailium

. . .

1I

1

~

A3 2,8,3 2,8,18,3 2,8,18,18,3 2,8,18,32,18,3

31

Indium

~ ~ ~

'l'hallium

-

1

Develo/~it~g cotzcept C16 about the nutnber of valence tile

Group Nunrber(l3) - 10 Valence electrons(3)

= Number

of

">

-

- - . -.

.

-

Methodology

Etlcolo.r~gesto write

the electronic configuration of Group 14

-

--

Hement

..

~tp-6

+ '

No. of electrons

Electronic Configuration

2,4 2,8,4 2,8,18,4 2,8,18,18,4 2,8,18,32,18,4

No. of Valence electrons

4 4 4 4

('arbon Silicon

~ ~

14

.- .

(iermaniurn

~

32

50

~

p

~

-

~

-

p

-

~

I ,cad

----

L

~

82

4

Dc\~clopitlgtlze corzcept CI7about the number of valence

c1ec.ti.or1.sr t ~(;I-oup 14 elernerzts

Group Nurnber(l4) - 1 0 = Nurrrber o f

,

\

Valence electrons(4)

%\

-

El~cozrrcrgrs write to

the electronic configuration of Croup 15

I Element

Electronic electrons

I

I

i

i Nitrogen

-~

~~

Arsenic -

-

{--T&i%3+4

1)c~l~c~lopitzg concept Clg about the nurnber of valence the

c.lec,(~.on.s C;/.oulp15 elernents ill

Group Number(l5) - 10 = Number of

, ,

Valetice electrons(5)

-

-

-

-

Methodology

@

,I,I

ACTIVITY (

Eticolo.~~gtls write the electronic configuratiori of Croup 16 to

1

&~~

Element

---

Electronic

-

-

Sulphur

I

1 Selenlunl

TF261

2,8,18,6

~-

l>cvcloping tllr c.oncept C I 9 about the rlurizber of valence

c~l~~c,r~.oiis it1 G'rvup 16 elelnents

-.~~

fi,'>,9\ /

\>-... -.

-.. .1 .

Group Number(l6) - 10 =Number of Valence electrorrs(6)

Etico~rrc~ges write the electronic configuration of Group 17 ro

1

Element Fluorine

No. of electrons

Electronic Configuration

:

I

, I

1 9 i

277

1 1 7 1

No. of Valence electrons

Bromine

. -

I

,

lodrne Astatine

~

2,8,18,18,7

85

2,8,18,32,18,7

-~~

-~

,

~

1~c~~~c.loping tlie concept CZ0 about the number of valence c~lc~.ri.otl.s G~.oup 7 elements ill 1

.--.---

, .

-. . .

Group Number (I 7) - 10 = Number of , Valerrce electrorrs(7) )

-

.

.

- -

Methodology

E~~c,olrt.trge.swrite the electronic configuration of Group 18 to

n

No. of Valence electrons

I)c~\,eloprrzg concept CI1about the number of valence tilt.'

Group Number(l8) - 10 =Number of Vale~zce electrons(8) except for

\

Neliunt (F1

Irl~n/~/\.rng r-oliltion between Group number and number the c~vc~lerrce electrorts (based on concepts

C,q

to CZ,)

(;roup Number = Number of Valence electrons

(;roup Number - 1 0 = Number of valence electrons

.-

-

Methodology

--. .

a

All elements in group 1 contain only 1 valence electron. All elements in group 2 contain only 2 valence electrons.

All elements in group 13 contain only 3

valence electrons. All elements in group 14 contain only 4 valence electrons.

All elements in group 15 contain only 5

valence electrons. All elements in group 16 contain only 6 valence electrons. All elements in group 17 contain only 7 valence electrons.

All elements in group 18 contain only 8

valence electrons except Helium (Helium has 2 valence electrons)

-

-

.

-

Methodology

1 1I

/

(I) In Group 1 and 2, the number of valence electrons is equal to group number. (2) From the group 13 to 18, number of valence electrons is equal to group number minus 10

.

_ I

EVALUATION

I

\

1 / 1

.~,Is,v~Y

the follon~ing:

( I ) How

many valence electrons are there in group 1 elements?

(2)An element X belongs to 1 3 ' ~ group. How many valence electrons are there in it? (3)An element contains 6 valence electrons. 'To which group it belongs?

( 4 )1 low many valence electrons are there in group 18 elements?

(5)Name the element having only 2 electrons In the group 18.

-

-

. .

Methodology

UNIT 14 PERIOD NUMBER AND NUMBER OF SHELLS

Per~od Number represents the number of'shells in an atom

~

PREVIOUS KNOWLEDGE

- ~ -

~.~

.Ctrrtients lruve learned the electronic cor$guration of c~lotnentsirnti provide opportunity to recall the concept o period. f

Etlc,orrt.ilge studrvlts to wvrite the electronic configuration of periotl 1 \k't.iting tlre electronic cotzjiguration of Period I

-~

.~

~-

Hydrogen lilen~ent 1 N o . of electrons 1 Electronicp--~ o n f i ~ u r a c o n . -p. 1 N o . of Sl~ells

~ ~

~ ~ p ~ ~

-

~~

~

-~

Helium 2 2 1

-

--

.-

Methodology

Developing tile cotzcept C22about the number of shells in the

j i r l ~ t e r i o ~eletnents p i

First Period elements contain only

--__-- -

Enco~ri.riges wrlte the electronic conjiguratiori of Period 2 to

Dcl,c,lo/~rtlg corlcept Czj about the rzul~lber- slzells irz the the of .scc~otrcl per-iotl elerner~ts

'-__-_-

--

Second Period elemerzts corztairz two slzells

I:'rlcolr/.c~ges write the electronic corlfguratiotr of main group to clerricrit.s in Period 3

--

-

-

-

--- -

-----

Methodology

I)ellc~lo/)~ng csoncept Czd nbout the nurnber ofslzells in the tile t11it.il/~c,r.iod elrt~renrs

~ ~

-

~

\

, ,

Tlrird Period elemerzts corttairz tlzree sltells

----

Enc,o~rt.trges n,r.,fe tile electrorric corrjiguratiorz of rnain group to

elerrrerrts irr Period 4

I

.

~~

-

i i

~p~

ri

Elerneut

E c

m

.

i

n m

-.

CI

3

~ ~ ~

. . . . .

--

No. of electrons

19

20

h , m

31 3 2

P ,

33

34

N ,

35

"!

36

" N

II

. .

Electronic ('o~~liguration

-

L

"

"

ern

* P "00

G

" t ,

z

4

N " 0

W ,

Oe

_oo

4

P

Z

l

Z ,

o \

L

, p

w 4

L

v

4

No. o f Shells

-

4

.. .

..

4

4

4

-..

!J)~'l'~'/O/llllgc,oncept Czs tllc. nbout the nurnber. of shells in the

,

~

.

Fourtlz Period elemerzts contaiit four

-

[I 01 ACTIVITY (

l:'~lco~o.r~ges to write the electronic conjiguration of main group

elernerrts irr Period 5

0

Y

-.-

5

52 53

54'

No. of

electrons

~~~ ~~

3 7 3 8

i

- .~~.

4 9 I

50

5

Eiectronic

L

3 3

L

c .

O0

3

"0 O

00

3

ti011

L

VI

"

QI

1

No. of

/ Sliells

!

5

5

5

!

L)c>\~c~lol~r~~g the cotlcept CZn about the nunzber of shells in the . / ~ / I / I p ~ ~ . r oeleuteizts d

-.--

--

-

-

Methodology

Eticout.czges to wrrtr the electronic configuration of main group

r1rn1c.rrt.sirr

Period 6

r i

-~

a

C

i

-~

~ ~

3

55

No. ill.

elecrrons

56

N

81

"

O " 00 " W

82

" N

"0 0

83

J

84

"

85

86

N

Electronic Contigur

ation

.

~-~~ -

"

,. w

W

3 3

u

U

Q

n

"0

L

S0 O

"

"

L

U P "0 0

-w " u

n

P L

L

" w C

"0 O W "!

"

O0

L

'J "

"

n

01

" O0

"

W

L

w " L w "

hJ " L w " w W

L

" N " W

n

" W

P

" a

w

"

4

No. o f

Sllells

~

' 6

~

6

~-

I

/ j ( ~ ~ ~ , l o tlzet C O J I C ~ CZ7 pl ~g ~ I about the nunlbe~ shells of

\

in the d

r utlr /)c~t.rotl cieriletzts

,

i<',c>, Sixtlt Period elements contain sir

\

--

-

~.

-

Methodology

Iderltlfyirtg the relation between period number and number of slrells. (Based on the concepts C22-C27),

Period Number represents the number of shells preset in an element

First Period elements contain only 1 shell. Second Period elements contain 2 shells.

Third Period elements contain 3 shells.

Fourth Period elements contain 4 shells.

Fifth Period elements contain 5 shells.

Sixth Period elements contain 6 shells.

Seventh Period elements contain 7 shells.

Methodology

~ ~

.-

1 1-

Period Number represents number of shells in an atom

the

I

I

EVALUATION

1 Atrrwer thefollowing que.stions:

( 1)

I

How many shells are there in the elements

of Group I ?

(2) How many shells are there in the elements of Group 2'?

(3) Name the group to which the element belong:.

(I)

(11)

(111)

Havlng 2 shells Havlng 5 shells

Hav~ng shells 3

(4) What is the relation between the No. of shells and the Number of the Period?

-

-

Methodology

UNIT 15

ATOMIC SIZE DOWN A GROUP

Learning Point

Atom~c size increases from top to bottom

in

a group due to increase in

number of shells

. .

~

~

~

PREVIOUS KNOWLEDGE

Students are encouruged to recall the following

c'otzcepls

J

Atom~c size 1s related to atomic radius ['he elements in a group contain same valence electrons

K-Shell can accommodate 2 electrons

J

J

J

L-Shell can accommodate maximum of 8 electrons

J

M-Shell can accommodate maximum of 18 electrons and

SO

on.

-

Methodology

-

DlSClJSSlNG THE CHARACTERISTICS OF A GROUP

Studetlts are encouraged t write down the electronic configuration o of Litlrium to Francium. (with the help of Periodic Table)

Li

11 19

j Sodiurn

Na

K

Rb 2, 8 , 8 ,

1 ~otassiurn

I

Cs

Fr

- . - ...

OUTDOOR ACTIVITY

/ I

/ '

/'

/'

Sevetl students of Standard IX are

~tzcouraged prepare display cards to

I

( N represents nucleus of an atom) and the

I

rest of'the students to prepare display cards showing

9

I

\\

(

\

represents electron). Students carrying tiisplt~y card N and that of e are asked to

-

-

--

-. --

Methodology

The ./ir.st student carrying display card N and the first one

carr,xirlg display card 'e' were selected and encouraged to rot-tn t l ~ structure of Hydrogen atom. r

Hydrogen

($ ..a.

.*

.......................

. I

.I

@..... . .... .. ....

*.

..a.

-1.

..

................ e

-

..

--

Methodology

The second student carrying display card N and the next three carr:ln1g display card ' e ' were selected and encouraged to forrw tile structure

of

Lithium atom.

Lithium

................................... .. ..' .I ... ..*. ..................... .... .....

*.

....... ........ ......................

..

I.

. -

-

--

.. .

Methodology

The t 1 t d student carrying display card N and the next eleven 1i. crrrr? rng cilsplq card 'e ' were selected and encouraged to

fotwl tlre rtrurtur-e of Sodium atom.

Methodology

-

7'/7efourth student carrying display card N and the next nineteen carr~~ing~ ~ p l a y 'e' were selected and encouraged to form the rl card strt1ctlrr.e of Potassium atom

L)e~,c,lo/~ the

cvrlcept Czsabout the relation between the size o f

the ritor?~ rzztrnber of shells (based on activity I to 4) ar~d

Size of the atom increases with increase in number of shells

-

. -

-

--- .-

--

227

-

-

- - - - - .-

Methodology

Studetrts are encourczged to draw the Bohr model of Hydrogen, Litlliutrl, Sodiutn, Potassium. Rubedium, and Caesium

,-.

i

I

(1)

!

Hydrogen

~

I

t ~-

Lithium

Methodology

-~

. .

~

-

Potassium

-- - -

---

. .

-

-

Methodology

--

-

Methodology

Caesiurn

. .

-

- --

--

Methodology

Develop tile cotrcepts Crs to C33ahout clzange in atomic size

tlo,c,ir flrr gi.o~cp

-.

Tlze Number of shells in an atom irzcreases as we move dowrr the group

The size of the atom increases as we

\ .

.move down the group _

/

Tlze size of the atom i~zcreases to due irrcrease in number of shells

Tlze f i s t elemerrt is tlze smallest atom

The last element is the biggest atom in tlre group

' -

--

-

-

---

-

Methodology

Atomic size increases from top to bottom Number of shells increases from top to bottom In a group, atomic size increases due to increase in number of shells

In a group, first element is the smallest

In a group, last element is the biggest

<

---. ,

I ,

I

i

\

Scientific Terms / Concepts

ATOMIC SIZE

,

\.

l ~ . .

- . \

-I

@

CONCLUSION

Atomic size increases from top to bottom in a group due to increase in number of shells

/ 4nswer thefollowing:

( I ) How many shells are there for elements in the first period?

I

1

I

I

I

(2) tiow many shells are there for elements in the second period?

(3) How many shells are there for elements in the nth period?

1

(4) Name the smallest atom in the first period ( 5 ) Name the biggest atom in the second period

(6) What happens to the size of an atom as

e-l-

I/

I

1

we move down a group? Why?

UNIT 16

-

ATOMIC SIZE ACROSS A PERIOD

-

F

Learning Point

Atomic size decreases from left to right in a period due to increase in the nuclear charge without ~ncreasing

-

the

number of shells

L

-

PREVIOUS KNOWLEDGE

~ ~

I'r-ovidr opportunity to recall the following concepts

Atomic size is related to atomic radius

J

'l'he elements in a group contain same valence electrons

K-Shell can accommodate 2 electrons 1,-Shell can accommodate maximum of 8 electrons

J

J

u

M-Shell can accommodate maximum of 18 electrons and

so on.

-

-

.-

-

-- .

--

Methodology

DISC'bSSING THE C7HARACTERISTICSO F A PERIOD

Stucient.~ are ~ncouraged to write down the electronic cor2f;gurulion of Lithium to Neon with the help of Periodic Table

Element

Elenlent Atomic No. Electronic

<:u~itiguration

.~~~ ~

--

-

-

-

-

Methodology

(OUTDOOR ACTIVITY)

/

/

/"'five T~'~ent.1,

/

students of Standard IX clre erlcouraged to prepare display c~ards sl~owing sign + the

8

represents proton of an atom) atzd atlother 25 students to make display cat~ls showing the sign

rlisj~la,~ + and that of - are asked card

Methodolow

1 1 ACTIVITY (

The first three students carrying positive cards are asked to keep their positions inside the first circle which represents the nucleus of' Lithium atom and three students carrying negative cards are asked to take their positions outside the circle in the order 2, 1 respectively in the 2"d and 31d circles which represent the first and second s ~ ~ c lrespectively. Three pieces of rope are taken and one ls end of each rope is tied to the students carrying negative cards.

.file tree end of each rope is given to students carrying positive

cards and are asked to pull the string with slight force towards the centre

Lithium (2,l)

-

--

- -

-

Methodology

1[]1 ACTIVITY (

'I'he next four students carrying positive cards are asked to keep their positions inside the first circle which represents the nucleus of Beryllium atom and next four students canying negative cards are asked to take their positions outside the circle in the order

2, 2 respectively in the 2nd and 3rdcircles which represent the first

and second shells respectively. Four pieces of rope are taken and one end of each rope is tied to the students canying negative cards. The lrec end of each rope is given to students canying positive cards and are asked to pull the string with slight force towards the centre.

Beryllium (2,2)

- .

-

--

--

Methodology

11I ACTIVITY (

The next five students carrying positive cards are asked to keep their positions inside the first circle which represents the nucleus of Boron atom and next five students carrying negative cards are asked to take their positions outside the circle in the order

2, 3 respectively in the 2ndand 3rd circles which represent the first

and second shells respectively. Five pieces of rope are taken and one end of each rope is tied to the students carrying negative cards. 'l'he lree end of each rope is given to students carrying positive cards and are asked to pull the string with slight force towards the cent1.e.

-

-

. . -- -

-

-

-

Methodology

0 ( ACTIVITY 1

(

The next six students carrying positive cards are asked to keep their positions inside the first circle which represents the nucleus of Carbon atom and next six students carrying negative cards are asked to take their positions outside the circle in the order 2, 4 respectively in the 2ndand 3rdcircles which represent the first and second shells respectively. Six pieces of rope are taken and one end of each rope is tied to the students carrying negative cards. The free end of each rope is given to students carrying positive cards

and :IIC asked to pull the string with slight force towards the centre.

.- .-

--____--*

-u

Carbon (2,4)

~

~

~

..

Methodology

~ ~

The next seven students carrying positive cards are asked to keep their pos~tionsinside the first circle which represents the nucleus of Nitrogen atom and next seven students carrying negatlve cards are asked to take their positions outside the circle in the order 2, 5 respectively in the 2ndand 3rdcircles which represent the first and second shells respectively. Seven pieces of rope are taken and one end of each rope is tied to the stud.wts-carrying negatlve cards. The free end of each rope is given to students carrying posltlve cards and are asked to pull the string with slight force towards the centre.

Nitrogen (2,s)

. -

--- -

242

-

-

---

. -

-

Methodology

01[ ACTIVITY

(

The next seven students carrying positive cards are asked to keep the~rpos~tionsinside the first circle which represents the nucleus of Oxygen atom and next seven students carrying negative cards are asked to take their positions outside the circle in the order

2, 6 respectively in the 2"dand 3rdcircles which represent the first

and second shells respectively. Eight pieces of rope are taken and one end of each rope is tied to the students carrying negative cards. The tree end of each rope is given to students canying positive cards and are asked to pull the string with slight force towards the centre

-

.

~

-~

-

~

Methodology

Developing the concept

C;4

to Cj6.aboutthe change in atomic

size trc,ross a period from Activities I to 6)

( 5 - ; L e a r attraction increases along a period

\___

0

'<-\

/

-

Number of shells remains the same along aperiod

Size of the atom decreases from leji to right along a period

-

- -

-

Methodology

Students are encouraged to draw the Bohr model of Lithium,

Beryllium, Boron, Carbon, Nitrogen, Oxygen, Fluorine and Neon.

Developitzg the concepts ubout the reason for decrease in size

(f~ f o l i ~ C Y O S SN period i

(C2y37to CdO)

(7

\/ -

,/ ;- ,

\

iVuclear attraction increases along a period

c7 . 3

Number of shells remains the same along

\_--

,/';7 Size of the atom decreases from left to ( ( c9) . 3 \ c ~ , . , / right along a period

1 .

,-----.

"

/---\'

Number of protons increases with number

- .

-

-

-

Methodology

--

-

Number of shells remains the same in a period Nuclear attraction increases on outer electrons

Atomic size decreases from left to right in a period.

11

First element in the group is the biggest atom.

a

1 ~ selement in the group is the smallest atom. t

-

I1

1 dT 7

s

n

(:ONLI.IIYION

( (

1

Atomic size decreases from left to right in a period due to the increase in nuclear charge without increasing the number of shells

-

EVALUATION

---

--

--

--

I

I.

Name the smallest atom in the second

period. Why is it so?

2. What happens to the size of the atom as

we move from left to right in a period?

3. Potassium is the biggest in the third period. Why?

-

Methodology

( TEST YOUR KNOWLEDGE

7\

(I) Name the following:

(1)

The scientist who designed the Modem periodic table

( 2 ) The scientist who first made a successful attempt in

classifying the known elements

( 3 ) The smallest atom

(4)

I'he biggest atom

( 5 ) 'I'he shortest period

( 0 ) The longest period

( 7)

rhe incomplete period

( 8 ) Number of'periods

0 ) Nu~nber groups of

( 10) Another (

name of First group elements

I I ) The first element in the Group I i 2 ) The last element in the Group 1

(

(

13) 'The first element in the Group 17

14) The first element in the Group 18 group of metals group non metals

(

( 15 ) A ( 16) A

(11)

Define the following:

( I ) Ciroup

( 2 ) Period

(3) Modem period~c Law

( 41 Mendeleev's Periodic law

(5 )

Transition elements

(111) Answer the following questions:

(I)

What happens to the atomic size as we move down the group'! Why'?

( 2 ) What happens to the atomic size as we move from left to right in a period? Why?

( 3 ) Where is the position of transition elements in the

periodic table?

(4) Where is the position of actinides and lanthanides in the

Periodic table'?

( 5 ) Where on the periodic table would you find

(i)

Metals

( i i ) Non metals

(iii)

l'he alkali metals

(iv) Halogens

~-

Methodology

I . Why was Mendeleev more successful with his Periodic Table than Newlands?

2. Compare Modern Periodic Table with Mendeleev's

Periodic Table 3 . What are the main characteristic features o Modem f Periodic Table?

4. Prepare chart o MODERN OERIDIC TABLE. f

5. Prepare an album including the contributions of

Lavoisier, johns Newlands. Dobereiner, Dmitri

Mendeleev and Moseley. 6 Draw the main groups (1, 2, a n d l 3 to 18) in the Modern periodic table.

(I 1

L . R.L)aniel, R. G. Scott and E. M. Edward (1993). Cltemistry-

Principle and Practice. USA: Saunders College Publishing.

(2)

R. M.Gallagher and P. lngram. (1994). Cltemistry. Oxford: Oxford

I lriiversity Press

(3)

li. M.Gallagher and P. Ingram. (1996). Cltemistry made clear.

Oxford: Oxford University Press

(4) 1) Garvie. K. John and A.Robertson (1993). '.

Oxford: Oxford University Press.

(51

Core Cltemistry.

H. Harrow (1927). Emittettt Clternists o Our Time. Van Nostrand, f

New York

I

( i . .]ones, M Jones and D. Acaster (1993) Clterrtistry. Cambridge:

('alnbridge Lniversity Press

(7!

('.N . I<.

Kao

(1 999)

Understanding

Cltentistry. Hyderabad:

I lliiversitics Press (India) Ltd.

(St

h1.H Kobcrt and James T. (1997). Science matters. Hyderabad:

I lnivcrsities Press (India) Ltd.

(01

.

R 'l'racy.. H.E. Tropp and A.E Friedl (1974), Cltentistry. Holt,

Ilinehart and Winston, Inc.

ACHIEVEMENT TEST IN CHEMISTRY

Std I Y Time: 1 Hour Max mark: 25 Instructions: Answer all questions

(I)

Choose the correct answer from the bracket (Each question carries 1 mark)

(I )

The b~ggest atom is (a)

(c)

Oxygen Fluorine

(b) (d)

Nitrogen Helium

(2)

1 lalogens belong to

(a)

(c)

Group1 Group17

(b) (d)

Group 2 Group 18

(3)

Which of the followtng is a transition metal?

(a)

(c)

Mercury ('opper

(b) (d)

Magnesium Iron

(4)

1 he incomplete period in the Modem periodic Table is

(a)

(c)

I

7

(b)

2

8

(dl

(5)

1 he number of valence electrons in the 1 6 ' Group elements ~

IS

(a)

(c)

2

I

(b) (dl

8

6

- -- - --

Methodology

(6)

I'he electronic configuration of an element is 2, 8, 7. How

many shells are there in it?

(a)

ic)

I

(b)

(dl

2

3

7

( 1 x6=6marks)

(11)

Find the odd one

(I )

(2)

Lithium, Strontium, Sodium, Potassium Potassi um, Calcium, Aluminium, Copper C'hlorine, Oxygen, Nitrogen, Magnesium Oxygen, Helium, Nitrogen, Fluorine

( 3)

(4)

( 1 x4=4marks)

( I l l ) Define the following:

(

I

)

(jroup Per~od

( 1 x 2 = 2 marks )

(2)

(IV) State the Modem Periodic law

(2xl=2marks)

(V)

Nanie 3 transition elements and write their uses

( 3 x 1 =3marks)

(VI) ('ompare the merits and demerits of Mendeleev's

I'er~odic table

(3xl=3marks)

(VII) I,ook at the table and answer the questions given below:

'I'he b~ggest atom The smallest atom Atom with highest electro negativity Atom with lowest electro negativity Halogen Alkallne Earth Metal

I rans~t~on element

Number of electrons in the outermost shell of B

SCHOOL OF PEDAGOGICAL SCIENCES MAHATMA GANDHI UNIVERSITY

KOTTAYAM

ATOMIC STRUCTURE

(STANDARD IX)

Prepared by

RAJESWARI. K

Supervised

:

Dr. EXEMMAL. J

(Supervising Teacher) Reader Departmerrt of Education U~riversiqf Kerala o

--

-

Methodology

Remedial

Teaching

Materials

on

the

topic

ATOMIC S'TRUCTURE is subdivided into 11 Units.

1)etails are given in pages 255-334. In each Unit, students are provided chances for observation, classification, ~dentification, discussion, analysis and concept formation.

Suitable charts, models, examples, illustrations, life situations are also used for developing new

conceptsiteaching points. Practice session is given at the end of' each unit to test the level of attainment of the students. Extended Activities and Reference Section are given. An Achievement Test on Atomic Structure is

siven at the end of the material.

~

-

--

-

-

CONTENTS

UNIT 1 UNIT 2 UNIT 3 UNIT 4 CONCEPT OF ATOM PARTS OF AN ATOM NUCLEUS OF AN ATOM ELECTRIC CHARGE OF PROTON, NEUTRON & ELECTRON UNIT 5 CONTRIBUTIONS TOWARDS THE DISCOVERY OF ATOMIC PARTICLES UNIT 6 UNIT 7 SHELL OR ORBIT CHARACTERISTICS OF ELECTRON CLOUD UNIT 8 RELATIVE MASS OF FUNDAMENTAL PARTICLES UNIT 9 UNIT 10 UNIT 11 ATOMIC NUMBER MASS NUMBER REPRESENTATION OF AN ATOM

--

-

-

-

- -

- . .

-

Methodology

-

INTRODUCTION

The first definite theory about the structure of matter was put forward by English Scientist and School I'eacher, John Dalton (1808). According to Daltons

atomic theory matter consists of small indivisible particles called atoms, which can neither be created rror be destroyed. Atoms of the same elements are alike irr all respects & combine witlz other atoms in sirtrple wlrole number ratios forming compounds or rtrolecules. Dalton's atomic theory remains undisputed

L I to ~

the end of 19th century & early 201hcentury showed

[hat the atom has a complex structure and is divisible.

7'Irese studies further revealed that the atoms are divisible into smaller particles called protons,

rr rlrtrorrs and electrons. Tlzese particles are regarded

us furrdant erttal particles because tlr ese are tlze

rrrairi cotrstituerzts of all atoms.

L

-

-

.

-

-

-

- .

- .

Methodology

~~

'I.

' Learning Points

~.

I

Atoms are the building blocks from which all the : materials in the world are made up of

2

i Every atom has a nucleus at the centre and electrons I outside the nucleus

Nucleus is the central part of every atom which consists of protons and neutrons Protons have positive charge and electrons have negative charge. Neutrons are electrically neutral The fundamental part~cles an atom are discovered by of sc~ent~sts as J.J. Thomson, Earnest Rutherford and such James Chadwick

3

6

~

1 he path of an electron around the nucleus is called shell or orb~t

~

.~~ 7 Electron cloud is the part of an atom in which there is possibility of finding electrons

/

8 9

. j

Relative mass of neutron, proton and electron Atom~c number is the number of protons in an atom or number of electrons in a neutral atom

--

1

. .

10

-<

/ Mass number is the total number of protons and neutrons

~ ~~ ~

II

Atoms can be symbolically shown using atomic number : and mass number

--

-

--

-

-

-

-

Methodology

LET US THINK AND

UNIT 1

- --

--

CONCEPT OF ATOM

.

Learning Point

Atoms are the building

blocks from which all the

niaterials in the world are made up of.

-

-

PREVIOUS KNOWLEDGE - -- --

Students at Secondary level might have learnt

that all

inaterials are made up of matter and the Fundamental unit of matter 1s the atom Molecules are formed by the combination of atoms Students are also aware that substances differ in their

propet ties due to the different type of atoms present in them.

Students are encouraged to think of twenty six letters

in the Etzglish Alphabet and the number of words that can be

developed by different combinations of the twenty six letters.

I

1 Each type o arrangement o htters make f f i difierent types o words. f

Fig. 4.1 1 Different words from letters

Etzc,our.r~ge students to compare the letters in words with tiny porticYrs

itz

suhstnrrces.

//'

/'

(

Words are composed of letters.

Similarly substances are composed of simpler particles called atoms.

'\\

\~-.\

__Z

-

--

--

Methodology

Students are given a set of match sticks and are encour.aged to develop dvferent Geometrical patterns using matcl~ sticks.

--

J

Fig. 4.12 Different Geometrical patterns from match sticks

-

-

-

-

-

.

Methodology

-

Encou~.ages students to make the following comparisons.

( I ) Letters- Word

(2) Match Sticks Geometrical Pattern

(3) Chalk Particles-Piece of Chalk

with

Atoms-Substance.

,'

---\

Atom

Substance (matter)

\

'. L--.

/ '

L,etters

t

I

a

Word

n

. .

Match Sticks

.

Pattern

1~ -

Chalk Particles

- -~

p ~ ~

0 Piece of Chalk

L)e\>c.loprngthe concept about co~zstituent matter of

/--, Atoms are constituents of all matter

. -

-

-

-

-

.

Methodology

Disctl.ssing details about the discovery of atom by Sir. John

Daltorr (1 766-1844)

weaver. was born in Cumberland, England. He began h ~ slifelong career as a teacher at a village schooi when he was only twelve.

Fig. 4.13 John Dalton

I

Seven years later he became a school principal. From his early

years to his death, Dalton carefully recorded the meteoric data

- - -

1 each day temperature, pressure, time, amount of rainfall and so /

forth. Dalton suffered from protanopia, an inability to distinguish colours at all. Much to his amusement his sight defect became known as 'Daltonism'

Dalton put forward the atomic theory in 1803.

\.--.

b -

According to John Dalton all matter is made up of tiny

I particles called atoms and atoms can neither be created I

nor be destroyed. Atoms combine to form molecules.

- -

- - ---

-

-

Methodology

-

Atoms are constituents of all matter.

1

\\

Atoms are the building blocks of all matter.

I

/

' .

/ '

Scientific Terms / Concepts

ATOM

--\

-Q

CONCLUSION Atoms are the building blocks from which all the materials in the world are made up of.

\-

J

Id

/

Atlswer

(I )

EVALUATION

thefollowing questions:

1

Define an atom.

( 2 ) Name the scientist who discovered that all matter is made up of atoms.

( 3 ) What are the contributions of John

blton?

j

-. . . . -

Methodology

UNIT

--

2

PARTS OF AN ATOM

-

--

f

Learning Point

kvery atorn has a nucleus at the

centre

and

electrons

outs~de nucleus the

~ - , - ~

~~

1'

PREVIOUS KNOWLEDGE

p ~

7-

i

r

o

t opportu?zif)~to recall that atonzs are the

c~or~stit~rents i1zatter. of all

Stlrderrr.~rrre provided opportunity to recall that the sun is the cetlt1.e o [lie solnr s,,,steirland the planets and satellites are tnoving / f 1-evo11~irrg .SUII rhrougl~ illr somefixed path.

-

.~

Methodology

Fig.4.14

Solar System

Comparing atom, nucleus and electron cloud with solar system,

sun and planets and satellites respectively.

~

.~

~

' \

Electron

('loud

-~ ~~

Planets and Satellites

/'

-~/'

-

-

-

-

-

Methodology

.J'tuderzts are encouraged to represent the parts of an cltorlr.

Fig. 4.15 Parts of an Atom

I

N ~ l c l e u s at t h e centre of the atom is

llectrons are present outside the

1111clcus.

-

--

-

-

.

Methodology

, ~ /

Scientific Terms / Concepts

3 '

---

0;

--

-: I1

CONCLUSION

Every atom has a nucleus at the

centre and electrons outside the nucleus

1

EVALUATION

I

.III.YVLEI- following:tile

1

1

(I )

Name the central part of the atom

(2 I Name the outer part of the atom

(3 ) Define the following:

(I)

i

..-

Nucleus

( i ~ )Atom

-

-

-- -

-

Methodology

UNIT 3

NUCLEUS OF AN ATOM

-

/ Learning Point

Nucleus 1s the central part of ecery atom w h ~ c hconsists of Protons and Neutrons

- .- - .. .

PREVIOUS KNOWLEDGE

f{rc,alling the position of nucleus and electrons in an

iltOlll

Discussirrg tlte cltaracteristics of Nucleus of an atom

Stude~tts are asked to draw a Circle using a compass and lh& Mark the centre

-

.

-

(1)

Nucleus I S the central part of every atom

Central Part:(Nucleus)

I

-

-

-

. .

(2,

Etymologically nucleus means the central part NUCLEUS = CENTRAL PART

1

Neutrons and Protons are

together

termed as

I

-

-

(5)

Mass of Nucleus

Mass o f the Nucleus is the total

mass of the protons and the neutrons

Mass of Protons

+

Mass of Neutrons

Nucleus is the central part. Neutrons and protons are present inside the nucleus Particles in the nucleus are called nucleons

1

Nucleus is electrically positive Electrons are present outside the nucleus

/ Scientific Terms / Concepts / i

/"

NUCLEUS PROTONS NEUTRONS

ELECTRONS

/

,\

'\

\

NUCLEONS

--.

is the part of I i atom Nucleus consistscentralProtons every 1 which of and

Neutrons

EVALUATION

( I ) Which is the centre of the atom?

I

1 (2) Where do you see the electrons?

I

1 1 1

(3 ) Where are the neutrons and protons seen?

( 4 ) Lkvelop models of nucleus for the

1 I

following atoms:

(i )

I

1

Hydrogen (No. of protons = 1, No. of neutrons = 0 ) Helium (No. of protons neutrons = 2 )

=

(11)

2, No of

(~il) Argon (No of protons neutrons = 18)

=

18, No of

--

-

-

Methodology

UNIT 4

-

ELECTRIC CHARGE OF PROTONS, NEUTRONS

AND ELECTRONS

-

,

\

Learning Point

Protons have positive charge

and electrons have negative charge.

Neutrons

are

electrically neutral

--.

- -~

~

.

~

PREVIOUS KNOWLEDGE ~~

~-~

L51udent.s encouraged to recall the following concepts: czre

1

Atoms are electrically neutral I- l o w of electrons causes electr~city

_I

- -

. - -~ -.

Methodology

~

[[pcTid>

Students ure encouraged to compare the charges

of protons, neutrons and electrons from the Table (4.1) given

belotr,

Table 4.1 Charges of protons, neutrons and electrons

p: r it ;

the

Charge

Relative charge

1 Neutron

I Electron

1 Positive charge. 1 Neutral charge

/ Negative charge

I

I

+1

1

I

-1

I

Protons have positive charge Electrons have negative charge

=

Neutrons are electrically neutral

-

- --

Methodology

Q

(1)

CONCLUSION

Protons are positively charged

1

I

(2) Electrons are negatively charged

(3) Neutrons are electrically neutral

I

3

--

EVALUATION

questions:

Arisuver the following

1

1

iI

( 1 )Name the positively charged particle in an

atom

( 2 )What IS the charge of an electron?

I

I

(3)Name the neutral particle in an atom (4)C'onrplete the table given below:-

I

Electrons . Neutrons

-

1

---------

UNIT 5 CONTRIBUTIONS TOWARDS THE DISCOVERY OF ATOMIC PARTICLES

Learning Points

'I'homson discovered electrons ( ~ i Earnest Rutherford discovered ) protons ( ~i )i James Chadwick discovered neutrons.

--

-

.

--

PREVIOUS

I'rovidlng opportunity to recall the contribzltions of

J J . Tllon~son. Ruthelford and James Chadwick

The existence of electron was first demonstrated by J.J. Thomson in

1897.118 189 7 Ire discovered that in

ilre

atom

there

are

negatively

Fig. 4.1 6 J.J. Thomson

charged particles of low mass. He

I

called these particles Electrons.

.

Earnest Rutherford was born in New Zealand in 1871. He was working on radioactivity. In 1911 Rutherford's experiments proved tlrat atoms contain positively charged particles equal in magrritude to the charge oj electrorls and mass greater titan tlrat of electrons. He named these pcrrticles as protoris.

Fig. 4.1 7 Rutherford

Irr 1911 Rutlierford's experiments showed the

esistrnce of a dense, positively charged centre, extremelj srrrull wkerr compared to the total size of the atom. He rrlrrrred this part as the nucleus.

Irr I Y32 Chadwick discovered that

crtorrrs corrtairt charge less particles al.so. H e called these particles as Nc,rrtroris. Its mass was found to be

nearly the same mass as that of a

proton.

Fig. 4.18

James Chadwick

. . .

-

-

Methodology

Electron was discovered by J.J. Thornson.

I

i

1

I'rotori was discovered by Rutherford.

( :hadwick

~

I-

discovered Neutron

. ,

, " /

,

/' Scientific Terms / Concepts

J.J. THOMSON

RUTHERFORD

I

--.

-

-

-

- --

Methodology

/

i

I

p;

1

CONCLUSION

(1) J.J Thomson discovered electrons.

(2) Rutherford discovered protons.

1i

(3) James Chadwick discovered neutrons.

I

iaFill in the blanks

EVALUATION

I

I

l

(I

)

Electron was discovered by------------

(2) Proton was discovered by-------( 3 ) ----was discovered by James Chadwick

/

( 4 ) The massive particles in an atom are-----

~~

-

~- -

.

Methodology

UNIT 6

SHELL O ORBIT R

Learning Point

I'he path of the electron around the nucleus is called shell 01 orbit

1

-

- .. -. .PREVIOUS KNOWLEDGE

-

-

- -

Slucients iiiigllt have learnt that electron cloud is a region \c,hrre clec,rrotis are found.

k;tzcc.)zrrclge the studerlts to draw the Diagrammatic

r.el)tc~.set~/ntior~s stritcture of atoms of Hydrogetz (H), Helium oj-the

(tic),Litkirtttt (Li) atrd Sodiutn (Nu).

,

~

1

Hydrogen

(2)

1

I j

!

Helium

I

Electron Neutron

!

I

I

. :

(3)

~ ~ ~~~ ~~~

Lithium

Electron Neutron Proton

\

~

Methodology

,

I

-

. ---

Sodium

Electron

Proton Neutron

Students

I

are

encouraged

to

compare

the

Diagrammatic

epl.csentatlons of' Hydrogen, Helium, Lithium and Sodium and

are encouraged to write the~r observations.

~

~~

.-

Methodology

Observations

n

The nucleus is at the centre of the atom The nucleus conslsts of protons and neutrons The electrons are present outside the nucleus Electrons are present in the circular paths called orbits or shells Hydrogen has only one electron The only one electron in the Hydrogen is arranged in path the first c~rcular There are two electrons in a Helium atom The two electrons in the Helium are arranged in the same clrcular path

9.

10.

'I'here are three electrons in Lithium atom The third electron in the Lithium atom is arranged in the second circular path.

11.

'l'here are 1 1 electrons in thesodium atom The first two electrons in the sodium are arranged in the first c~rcularpath, the next eight are arranged in the second c~rcular path and the eleventh electron is arranged in the third circular path

12

-

--

-

Methodology

Encozonge stutlents to answer the following questions based

on tlrr observations

I . I 4hy

I S the

second electron enter in the first path itself?

1 he Flrst Shell can accommodate maximum of two electrons

-

2. W h y

3. Why

IS

the thlrd electron enter the second path? the eleventh electron not occupied in the second path

IS

itself'!

Ucveluping the concept of electron shells

,

,

i

Electron shells are Circular path of the electron outside the nucleus

lItrc,our.trgcto narne dqfeerent electron shells

-

, _ !

/

-

_+--

.' ,

i

\

Electron Shells may be named

either

1, 2, 3, 4,

or

-. ..

--------

'\

\. ..

K, L, M,

N, -------

Methodolow

Delleloping the concept of structure of atoms through

c,la.tsr-oonztzctivity (Phuse 1 to 3)

i

I

A leader was selected from Std. IX and was

provided w ~ t h card representing nucleus a

I

0 I

The other students were provided with one card each, representing an electron

*

I

0

?'he teacher writes the name of an element

(

llydrogen, Helium, Neon, etc.) on the blackboard.

I he leader of the team carrying the card of nucleus

takes his position at the centre. The members holding tlie cards with electron has to form a circle representing an electron in a shell and finally the

students make the structure of the element written on tlle blackboard.

- ----

Methodology

I)rcig~~rrrnnluticrepresetztation of the classroom activity

.sllo~c the s1r.lcc-lure ofntorns itrg

Hydrogen

.................. .- K ~ht&'-..

b

(. [email protected] ?

+................... -..

Helium

$g)$

...............--.*.. +...

K Shell

..-.. ..-. ..............

xi-..-v '

Phase 3)

Neon

J ' \

...

................... .... ...

*K Shell

I't.o~,rcic>oppot.tzrtllty to,fiizciout the capacity of electron shells

/

/

, -

,,A

Shell

I., Shell

IZ1 Shell

2 electrons

/

~3 8 electrons

I

\

a 18 electrons

0 electrons 32

IV Shell

-

. --

Methodology

l:'t~cot~rccge students to draw the structure of Hydrogen,

Helirinr, Litltiunt and Cltlorine and Argon

1 proton

1 electron

, ,

1

1,

, ,

.

~

'.

(1 electron)

Proton

Fig. 4.19 Hydrogen atom

- -

-.

Methodology

Structure of Helium atom

,__

. . &.

\..

2 protons 2 electrons

K Shell (2 e)

,/

Fig. 4.20 Helium atom

2

\

, . -

11

-.

--+-*,'

K Shell is the lowest level which

can accommodate upto 2 electrons

Structure of Lithium atom

-

3 electrons

. O - -, - - - ..

\

<13>

0

KSheIi(2e)

\

"

,

'\ . . . \

/

L Shell ( 1 e )

/'

/

.

-

. ._---

Fig. 4.21 Lithium Atom

c = electron

Structure of Chlorine atom

Fig. 4.22 Chlorine atom

upto a maximum of - 8 electrons.

-

. -

Methodology

Structure of Argon atom

18 electrons

-

20 neutrons

K Shell (2 e) L Shell(8 e)

, \

\

- -. --./ -.

-

M Shell(8 e)

r-i

\\

--- 9 3 . - ' 2

\.. . .

. <;t-.---c

~~

Fig. 4.23

Argon atom

-

~~-~ - - - ~ ~

I hll Shell is the third

-.

I1i;txlrnunl

of 18 electrons

~~

I!?I Shell

.

can hold upto maximum of 32 electrons

-

--~-.

.

Methodology

Strucrur~ng model fbr representing the main constituents of atom

, /

, the atomic

centre

\

centre Cluster together to form

( 7

Nucleus

Electrons mo\.lng round very l'asr around Ilic 1111cleus at cl~llkl-e~r~ le\:els

'\

~-./.

Together becomes

(

ATOM

ELECTRON SHELLS

, "

,/'

/"

/

= w

K SHELL

L SHELL

G

M SHELL

N SHELL

c

Fig. 4.24 Structural representation of atom

Stlr~1r11t.s c>l~c,our-ageri calculate the maximum number of rrr-e to elecft.oils tlzc~tcan he accommodated in each shell given in (lirblc. 4 17)

Table 4.2 Maximum number of electrons that can be accommodated in the shell

NO.

of Shells

Shell

Maximum Number of Electrons That can be accommodated In the shell

Attention

-- ~ ~ ~

I<lectron shells are imaginary circular paths of the clectron.

I< Shcll can hold a maximum of 2 electrons.

I . Shell can hold a maximum of 8 electrons.

M Shcll can hold a maximum of 18 electrons.

N Shell can hold a maximum of 32 electrons.

n'" Shell can hold a maximum of 2n2 electrons.

- . - . .-

Methodology

,

1

,'

/

__ ---

Scientific Terms / Concepts

-CONCLUSION

The path of the electron around the nucleus is called shell or orbit

,7-

I

A

(

EVALUATION

1I

I

I ) Define an electron shell

K shell can hold a maximum of electrons. (11) 1. shell can hold a maximum of electrons ( l i l ) n"' shell can hold a maximum of electrons ( 3 ) Match the following:

(I)

-~ ~

( 2 ) Fill in the blanks.

I

Number of Electrons -- -. .

8

1

(4) Draw the atomic structure of the following

I

i

i

I

i i

.

~

atoms ( i ) Hydrogen (atomic number = 1) (atomic number = 6) ( i i ) Carbon (atomic number = 1 1 ) (iii) Sodium

- ~~

J

297

UNIT 7

-

-

CHARACTERISTICS OF ELECTRON CLOUD

. .

-

--

- - - Learning Point

llectron cloud is the part of an

poss~bility finding electrons of

.

.

.

- ~~-~

..

-\ J, I /

PREVIOUS KNOWLEDGE

>

/.(*I

/lie stutler2ts discuss the special features of the

o l ~ ~ c ~c.lo~cd r ~ citorn ~ i ~ oof'a11

S ~ i l i t(11.c~ e ~ z c ~ u ~ a gto d represent pictorially the e

c.lraruc~teri.stic.s rlectron cloud of

Electron cloud is

a region in which electrons are found

Electrons in the electron cloud circle very fast around the nucleus

Electron cloud is the electrically

negative part of

( an

atom

(4)

Electrons circle at dif'ferent levels in the electron cloud called

electron

1 shells or orbits

--

- . -- -- -

Methodology

--

-

Each orbit can hold

a definite number

1" Orbit-2 Electrons

2"dOrbit-8 Electrons

3rdOrbit-18 Electrons and so on

of electrons

Electron (-loud I S the

lighter part

o l thc atom

-

--

- -

-

.

Methodology

4

-

Attention

--

Atoms are built up of protons, neutrons and electrons Protons and neutrons are present in the nucleus

The electrons revolve in orbits around the

nucleus

-

\

1 .

.\-

ELECTRON CLOUD

&

CONCLUSION

Electron cloud is the part of an atom in which there is possibility of finding electrons

Answer the following questions:

(

( 1)

What do you mean by an electron cloud?

II

(2) Define an electron shell

/

(3) Give one word answer:

(i) Imaginary path through which

electrons revolve

1

(il)

Where do you see the electrons?

I

UNIT 8 RELATIVE MASS OF FUNDAMENTAL PARTICLES

Learning Points (i) Protons and Neutrons have

a mass approximately one

( ~Electrons have a mass i)

111840 relative to the mass

of a Hydrogen atom

I

- -~

PREVIOUS KNOWLEDGE

~-

Rec,nlling the following concepts

Nucleus contains protons and neutrons

u

Electrons are present outside the nucleus

u Nucleus is the heavy part of an atom u Mass of nucleus is the total mass of protons and

neutrons

Students are encouraged to draw the structure of ltycfrogen atorn.

P~.o\~i(Ie opportutzily to identih the relation between the mass

c?f HlrIrogen atom and the mass of a proton (discussion and

I

(11)

No. of electrons in a Hydrogen atom.

No of protons in a Hydrogen atom.

(1) (1)

( 111)

(IV)

\ \

' \

No. of neutrons in a Hydrogen atom

(0)

The massive particle in a Hydrogen atom(1 Proton)

-

-

-

. - ..

Methodology

Students are encouraged to prepare Table showing the mass of fundarneiztalparticles with respect to the mass of hydrogen atom.

Table 4.3 Mass of fundamental particles with respect to mass of Hydrogen atom

-

Proton

-

I

Mass

Nearly equals to the mass of hydrogen atom Nearly equals to the mass of hydrogen atom

1

Position

Nucleus

Neutron

1

Nucleus Outside Nucleus

I

protons and neutrons

--

-

-

Students arc7 encouraged to prepare Table showing the nppro.rimate selative mass of fundamental particles.

Table 4.4 Approximate relative mass of fundamental particles

I

1

- 1

Proton

I

7 0 HYDROGEN

HYDROGEN ATOM)

/Ieu6111

Electron

-

-11.

i

1

1

Equal to Hydrogen Atom Equal to Hydrogen

compared to Hydrogen Atom

-

(Mass of electron is

considered as Zero)

-

Provlde

opporturlity

to

compare

the

Diagrammatic

representutiot~s masses ofproton, neutron and electron. of

(

the masses of

1

Equal Mass for Proton and Neutron

and n neutrontn)

I

-\

C'oruparing the masses of

a proton (p)

\

and a

I tydrogen ( H )

L7~ ~

Equal Mass for Proton and Hydrogen

a

--

. ~ - - -

masses o t a proton ( p )and a electron (e)

Mass of e ectron is very small when compared to mass of proton in an atom

-

Methodology

Protons and neutrons in atom have almost equal mass.

'I'he mass of an electron is approximately zero.

/

'

/'

I

Scientific Terms / Concepts

MASS OF ELECTRON MASS OF PROTON

1

--

Methodology

0

CONCLUSION

(1) Proton and Neutron have mass

approximately one

(2) Electron has zero mass

EVALUATION

(I)

I

What is the relative mass of proton?

( 2 ) What is the relative mass of neutron?

(

( 3 ) What is the relative mass of electron?

( 4 ) Name 2 fundamental particles having

I1

I

--

-

-

-- -

-

.

-

Methodology

UNIT 9 ATOMIC NUMBER

Learning Point Atomic number of an element

IS

the number of protons in

cach atom or the number of electrons 1r1 a neutral atom.

-

PREVIOUS KNOWLEDGE

C

1'1.or~~d~rig opportunzty to recall the following concepts:

J

U~fferent atoms have different number of protons An atom has equal number of protons and electrons An atom possesses mass which is due to the presence

of nucleus.

J

A

~~

.

_ _

Methodology

DEVELOPING THE CONCEPT OF ATOMIC

NUMBER

(I )

Erzcourage students to draw the structure of Oxygen

c~torll

(Atomic number of Oxygen 3 8 )

Fig. 4.25 Structure of Oxygen atom

Methodology

(2) ltientlfi~ngthe rzumber of protons and electrons in an

o.y\gerz

trtoril

(zf atomic number is given)

Students are encouraged to calculate the number of protons and electrons in an Oxygen atom to identify the relation between the

number of protons, number of electrons and atomic number.

.-

-

-- -.

Number of Protons Number of' electrons Atomic number Nutnber of: Protons Number of Electrons Atomic Number

(A~omic Number

=8 = 8

= 8 (Given)

= = =

=

Atomic Number Number of Protons Number of Electrons

Number of Electrons in a

Neutral Atom)

-

-

-

.

-

-

--

Methodology

Stude11t.r are directed to establish the relationship between otorrllc number, number c?fprotons and number of electrons Ji-orr~ 7irhle 4.5

Table 4.5 Atomic number, number of protons and number of electrons of elements

Hydrogen

-~

~

--

Helium <:arbon

--

2

2

2

6 8

~

6 8

11 17

6

Oxygen

-

8

11 17

Sodium

- .

11 17

('hlorine

--

- . - -

Atomic Number

= Number

of Protons =

Number of Electrons

(~t&&ke&to&ofebina~datcpn)

. -

-

- --- . . -

Methodology

Attention

In an atom electrons and protons are equal in number. 'I'he number of electrons or protons are referred to as atomic number

i

,~ - ~ ; i e n t i f Terms / Concepts / ic

--.-

ID

1 I--

CONCLUSION

Atomic number is the number of protons in an atom or number of electrons in a neutral atom

I

EVALUATION

1

I

(1 ) Define atomic number

I

(2) What is the relation between the atomic number and number of electrons?

(3 ) What is the number of protons and electrons in an atom with atomic number 17'?

(4) What is the atomic number of an atom containing 10 protons?

1

-

-

-

-

--

Methodology

UNIT 10

MASS NUMBER

Learning Point

Mass number of an element is the total number of protons

and neutrons present in an

1

atom.

I

- -

PREVIOUS KNO

Proviciing concepts

opportunity

to recall

the following

o Nucleus is the massive part of the atom

u

Protons and neutrons are the massive particles and are present inside the nucleus

u

Every atom has mass.

-

- -

-

- - --

Methodology

DEVELOPING THE CONCEPT OF MASS NUMBER

Encourage students to represent the structure of

CARBON, OXYGEN And SODIUM A TOMS

Fig. 4.26 Structure of Carbon atom

Provide opporturzity to calculate the mass number of Carbon

~-

Number of protons Number of Neutrons

Total Number of massive particles

=

6

6

\

= =

=

6+6=12 12

'l'herefore MASS NUMBER

\

J

--

-

--

Methodology

Fig. 4.27 Structure of Oxygen atom

Provide opportunity to calculate the mass number of Oxygen

atorll

f

Number of protons Number of Neutrons

= 8 = 8

\

Total Number of massive particles = 8 + 8 = 16 Therefore MASS NUMBER

=

16

~~

~.

Methodology

Figure 4.28 Structure of Sodium atom

Provide opporturzity to calculate the mass number of Sodium

aton1

/

,

Number of protons Number of Neutrons 'Total Number of masslve particles 'Therefore MASS NUMBER

=

= = =

11 12

1I

+ 12 = 23

23

Ider~tlj~zng relation between mass number, number of the protor~srlrzd number of neutrons.

-

-

-

-

-

Methodology

1 ( ACTIVITY 1

(

Students are encouraged to recall the number ofprotons and neutrons in the Hydrogen atom and calculate the mass number.

/

I

---

Number of Protons

=

1

I

Number of Neutrons = 0

Mass Number

=

Number of Protons + Number of Neutrons

=

-

1

+

0

=

1

--

-

-

-

-

A

-

Methodology

Providing opportunity to find out the atomic number, Mass number. No. of electrons, no. of protons, and no. of neutrons using the Table

Table 4.6

Number of electrons, protons, atomlc number and mass number of elements

Using Table 4.6 students write the number of electrons,

protons, neutrons, atomic number and mass number of Hydrogen, Helium, Carbon, Oxygen, Sodium, Chlorine, Nitrogen, Neon, Magneslum and Sulphur

.

-

-

--

-

Methodology

Developing the equation showing the relation between number of neutrons, mass number and atomic number

Number of neutrons = Mass number - Atomic number

C/Ib))Attention

Mass Number is equal to the total number of protons and neutrons

//

,

Scientific Terms / Concepts

MASSNUMBER

2 _ -

L. .

l _

I

/

Mass number of an element is the total number of protons and neutrons present in

I

Methodolorn

(d.

/

(1)

EVALUATION

I. Answer thefollowing

I

Define mass number? atomic number is 13. Find out the number of protons, electrons and neutrons present in it?

( 2 ) The mass number of A1 is 27 and

11. Exurnine the table given below andfind out

the

missing numbers (proton /electron/

ileutron/atonzic number/mass number)

Number of 'Iectons trons trons

Element

I

I

Atomic Number

Mass

Number

-

Beryllium Mazesiurn

---

-----

Sodium.

-----

---

23

-

-

- .-

Methodology

UNIT 11

--

REPRESENTATION OF AN ATOM

Learning Point

All atoms can be represented by uslng mass numbers and

atomic numbers

Providing opportunities to recall the following concepts

J

Symbols are short hand representations of atoms Symbol represents an atom of the element

u

Familiarizing the symbolic representation of atoms

l?rample I]

7

-up\

/

1

Symbol for Hydrogen atom Atomic number of Hydrogen Mass number of Hydrogen

1

1

+1 1

I

/

~

~

~~

Methodology

Provide opportunity to represent the short hand notation qf Hydrogen atom

Providing opportunity to complete the Table 4.7 showing

the relation between atomic number, mass number, no. of

electrons, no. ofprotons and no. of neutrons.

Table 4.7 Relation between atomic number, mass number, no. of electrons, no. of protons and no. of neutrons

-

-

-

-

-

-. .

--

Methodology

Students are encouraged to represent short hand notation of Neon, Carbon and Oxygen atoms

/

, /

/'

Symbol for Neon

/

i

+ Ne

10

Atomlc Number Mass Number

-

a

-

\

\

'\-. i

\

' \

~~

~~

Methodology

Methodology

Representing the short hand notation of an element

Mass Number

SYMBOL

Atomic Number

I

Mass Number SYMBOL Atomic Number

0

I

CONCLUSION Atoms are represented symbolically using symbol, atomic number and mass J

1 2

( 1)

-

EVALUATION

I

I At~swerthe following:

Find out the number of protons, neutrons and electrons present in the atoms given below. Carbon, Nitrogen, Sodium

( 2 ) Draw the models of the above atoms.

(3) Write down the short hand form of the following atoms.

I

I

1

1

I

d

(a) Oxygen (c) Boron

(b) Calcium (d) Copper

-

Methodology

-

-

( 1)

Draw the structure of the following atoms showing the nucleus containing protons and

1

neutrons and the orbits with the respective electrons.

( i ) Lithium

( i i ) Aluminium (iii) Silicon

( i v ) Calcium

(2) Prepare

an

album

including

the

major

contributions of J.J. Thomson, Rutherford and James Chadwick.

(3) Prepare a radio talk on the discovery and

1

properties of electrons, protons and neutrons.

- -. . .

--

-

--

-

-

-

-

Methodology

TEST YOUR KNOWLEDGE

(1)

Name the following: (i) (ii) the basic unit of matter the sub-atomic particle with positive charge and unit mass (iii) sub-atomic particle with no charge and unit mass (iv) the shell that can hold a maximum of 18 electrons (iv) the scientist who discovered electrons

(v)

the particles present inside the nucleus

(2)

Define the following:

(i)

nucleus

(ii) Nucleons

( i i i ) Atomic number

(iv) Mass number

(1)

electron shell

(3)

Name the scientists behind the discovery of electrons, protons and neutrons.

(4)

Why is sodium atom electrically neutral?

(5)

(6)

Explain the parts of an atom Draw the atomic structure of the following atoms: (a) Lithium (b) Neon (c) Sodium

(7)

What is the relationship between atomic number and mass number?

(8)

Write down the number of protons, neutrons and electrons present in:

( i ) Chlorine atom(Atomic number = 17, Mass number

=

35) and

(ii) Calcium atom)Atomic number = 20, Mass number = 40)

(9)

Develop models of the nucleus for the following atoms:

(a) Helium

( 10)

(b) Chlorine

Explain the charge and mass of fundamental particles in an atom.

(1)

L. R.Daniel, R. G. Scott and E. M. Edward (1993). Chemistry-

Principle and Practice. USA: Saunders College Publishing.

(2)

R. M.Gallagher and P. Ingram. (1994). Chemistry. Oxford: Oxford University Press

(3)

R. M.Gallagher and P. Ingram. (1996). Chemistry made clear. Oxfbrd: Oxford University Press

(4)

U. Garvie. R. John and A.Robertson (1993).

Core Chemistry.

Oxford: Oxford University Press.

(5) B. Harrow (1927). Eminent Chemists of Our Time. Van Nostrand,

New York

((I)

C;. Jones, M Jones and D. Acaster (1993) Chemistry. Cambridge:

Cambridge University Press

(7)

C'.N.R. Rao

(1999)

Understanding

Chemistry. Hyderabad:

llniversities Press (India) Ltd.

(8)

M.H. Robert and James T. (1997). Science matters. Hyderabad: Universities Press (India) Ltd.

(9)

C;. R. Tracy., H.E. Tropp and A.E Fried1 (1974), Chemistry. Holt,

Rinehart and Winston. Inc.

-

-

-

-

-

Methodology

ACHIEVEMENT TEST IN CHEMISTRY

( SECONDARY LEVEL )

Time: 1 hour

Max. Marks: 25

Instructions: Answer all the questions (A) Choose the correct answer from the bracket.

(1) Electron was discovered by (a) J.J. Thornson (c) Rutherford (b) Chadwick (d) John Dalton

(2) 'l'he central part of the atom is called

( a ) Electron

(b) proton

( c ) Neutron

(d) nucleus

( 3 ) 'fhe maxlmum number of electrons that can be accommodated

In the second shell is

(a) 2

(cl

(b) 8 id) 32

18

(4) I'he sub-atom~c particle with a positive charge and unit

'S

- -

mass

( a ) electron

(c)

(b) proton

neutron

(d) positron

(5) The shell nearest to the nucleus is

(a) K

(b) L (d)

(c) M

N

(6) Atom~c number of Phosphorous is 15; its number of electrons

in the atom will be

(a1 (c,

2

(b) 8

10

(4 15

(7) The particles which are equal in number in an atom are ( a ) proton & neutron

(c )

(b) neutron & electron

(d) nucleus & proton

proton & electron

(8) 'file neutral particle in an atom is ( a ) electron

( c neutron

(b) proton (d) nucleus

(9)

1 he mass number of magnesium is 24 and has 12 electrons.

'I he number of neutrons will be

(;I)

II

(b) 12 (dl 23

(c,

21

(10) Uas~c: fundamental unit of matter is ( a ) molecule

(c 1

(b) element

(d) ion

atom

( 1 x 10 = 10 marks )

-

--

-

--

-

Methodology

(B) Define the following:

( a ) Electron shell

( b ) Mass number

(c) Nucleons

( 2 x 3 = 6 marks )

(C) Explain why atom as a whole is neutral with a suitable

example.

( 4 x 1 = 4 marks )

() I)

Draw the structure of the following atoms showing the nucleus containing protons and neutrons and the orbits with the respective electrons.

( a ) Nitrogen (Atomic number = 7, Mass number = 14)

( b ) Silicon (Atomic number = 14, Mass number = 28)

(2,12 2 = 5 marks ) x

( I l l ) ACHIEVEMENT TEST I N CHEMISTRY

The Investigator prepared an Achievement test in Chemistry for Educationally Backward students studying in Standard IX

based on the topics selected for the preparation of Remedial Teach~ng Materials

74 test items were included in the draft test.

Twenty

multiple choice questions are included in Section A

(one mark

allotted for each item). In Section B there are ten questions and students have to answer in a word or in a sentence; one mark allotted for each question. Section C consisted of six short Separate answer

answer and one short essay type questions. sheets were provided to students.

ltem Analysis

ltem analysis is concerned primarily with two characteristics of items namely item difficulty and item discriminating power. Item analysis

IS

done to find out the suitability of the test item. Any

test can be improved through selection, substitution o r revision of items. The total scores obtained for each

candidate was calculated b y summating the scores o f the individual items. The 300 response sheets were arranged in the descending order of the total scores. The top 27 per cent and bottom 27 per cent were used for item analysis.

-

.-

-

~

Methodology

The scores for each item in

both groups were used for

calculating the Discriminating Power (DP) and Difficulty Index(D1) of each item. Items with Difficulty Index (Dl) between 0.37 to 0.6 and Discriminating Power (DP) above 0.4 were selected for the final test. The selected items were printed i n booklet form with all necessary instructions. A sample of the final test is given in

Appendix 11. (The Achievement test was prepared on the basis of

the Blue print)

Validity & Reliability of the Tests

The procedure adopted for the construction of the final test provides complete evidence for the validity of the test. Face

validity of the test was ascertained by subjecting the test to assessment by experts, for their comments. The content validity of the test has been ensured through the choice of items and the test construction procedures. The

reliability of the test was found out using Split-half Method. The Correlation test scores for the two halves was found out using the Pearson's Product Moment Coefficient of Correlation. The

reliability of the half test was 0.72. It was corrected by SpearmanBrown Prophecy Formula. The coefficient obtained was 0.84.

which shows that the test is highly reliable for the purpose.

SCORING K E Y OF ACHIEVEMENT TEST

Scoring key is given in Appendix Ill

VA1,IDATION O F REMEDIAL PROGRAMME DEVELOPED

The suitability of Remedial Teaching Materials in Chemistry prepared for Educationally Backward students studying

in

Standard IX was assessed by submitting the Remedial Materials to experts in the field of Chemistry. suggestlons made by them, In the light of the valid modifications and

appropriate

corrections were made in the Remedial Materials prepared. The responses in the schedule were then subjected to statistical analysis. The details of the Evaluation Schedule are presented in the Analys~sPart (Chapter V). The list of experts are given as

Appendix I V .

(IV)

I

N

SCALE

FOR

EXPERTS

AND

SECONDARY

S('11001. CI-IEMISTRY TEACHERS

A rating scale was prepared by the investigator to collect

details regarding Remedial Instructional Materials on the following aspects.

(I)

Suitability of the Remedial Instructional Materials

Availability of the resources

(11)

(111)

Practicability

The respondents were asked to go through the concepts given in the rating scale and indicate their opinion by putting a Cross mark(>() in any one of the three columns, viz., Great Extent(GE), Some Extent(SE) and Not at AII(NA) [Appendix-Vj

(V)

QUESTlONNAIRE FOR EXPERTS AND TEACHERS (AT SECONDARY SCHOOI, LEVEL)

(1)

Questionnaire for Experts

A questionnaire covering three major aspects was prepared

to collect the responses of Experts regarding the following dimensions: (i)

(ii)

Necessity of Remedial teaching Need for special training for Secondary school

Chemistry teachers in Diagnostic testing (iii) Need for special training for Secondary school

Chemistry teachers in Remedial Teaching [Appendix

vr]

(2)

Questionnaire for Teachers

A questionnaire covering six major aspects was prepared to

collect

the

responses

of

the

Secondary

school

Chemistry

Teachers regarding the following dimensions:

~

-~ .

~~

~p

Methodology

(i)

Necessity of Diagnostic testing and Remedial Teaching training for Secondary school in Diagnostic testing and

( ~ i ) Need for special Chemistry teachers

Remedial Teaching

( ~ i i ) Extent of Practice (Diagnostic testing and Remedial

teach~ng)

(IV)

Procedures

adopted

in

Diagnostic

testing

and

Remedial teaching (v) Practical difficulties teachers while likely to be encountered by Diagnostic testing and

practicing

Remedial teaching

(VI)

The suggestions of Secondary School teachers for the effective use of Diagnostic testing and Remedial teach~ng in Chemistry at Secondary [Appendix VII]. School Level

(VI) (;ENERAL D A T A SHEET

A general data sheet was prepared and administered along

with the other schedules to collect personal details about the students like sex, locality of school, medium of instruction. management of school, income and educational status of parents (Appendix VIII).

.

-

-

. -

Methodology

4.1.2 S A M P L E SELECTED FOR THE STUDY

The deta~ls regarding the sample selected for the study are given below: (i) The investigator selected 620 Educationally Backward

students [based on the annual examination achievement test scores of all school subjects in Standard VIII, First unit test and first terminal (Examination) achievement test scores of the same students in Standard IX] studying in X standard 1 of different schools in Kollam district. (On the basis of Achievement tests students scoring less than 30% for all school subjects selected as Educationally Backward students). (ii) From the 620 Educationally Backward students

300

students scoring less than 30% in Chemistry were selected for experimental study (The details are given in Table 4.8). W h ~ l eselecting the sample, care was taken to give due representation to variables like sex, locality, management, community, income and educational status.

Table 4.8

The Sample selected for Experimental Teaching

SI.

Yame of Schools

I

-

-

-

11

7

Sex Male

I

Locality

Management Govt. I Pvt.

Female I Urban 1 3 1

i

Rural

Medium of Instruction Eng i Mal

Educational Status High I Low

I

Type of Teaching

Total

I

'

I

20

6

3.

I

Govt. Girls H.S. Chavara St. Joseph G.H.S. Neendakara Govt. Girls H.S, Vallikkeezhu Vimala Hridaya GHSS, Kollam St. Aloysius HSS, Kollam

15 30

20 10 20 14 23 20 20 14 23 20 20 15 30 10 20 10 20

20

4

9

16

' 20

10 20 14 23 20 20 15 30 20 10 15 15 10 15

11

6 14

10 23

i

LM SL

20 20

4.

4 6 4 15 16 15 14

5.

14 23

6.

7.

5 4

SL LM

20 30

16

TOTAL

Note: RT -Remedial Teaching LM - Lecture Method SL - Self Learning

300

$ s

. -

-

--

- --. - -

Methodology

(iii)

The Rating Scale was administered to 16 experts and Secondary School Chemistry Teachers.

54

(iv)

A questionnaire was administered to 16 Experts and teachers in Chemistry at Secondary School level

54

(v)

The general data sheet was administered to the 300 students selected for experimental study

4.1.3 EXPERIMENTAL DESlGN AND PROCEDURE

The basic experimental design adopted in the present investigation was Pre- test Post- test parallel group design. Standard Students from The ~nvestigatorselected 300 I X ' ~ seven Secondary Schools for the Experimental study. The topics selected for experimental study were Periodic Table, Atomic

Strirctrrre urrd Oxidafiorr arrd Reduction. Care was taken to give

due representation to Sex,

Locality, Marragemerrt of Schools

,

Medirrnr ofirrstructio~r and Educational status of parents.

After selecting schools for the experimental study, the investigator made necessary arrangements with the heads if the schools selected for conducting experiments.

The investigator adopted three methods for teaching the topics. The details are given below:

Remedial 'Teaching using Remedial Teaching Materials

Metllod I 1

Self learning Method using Remedial Teaching Materials prepared

Method Ill

Lecture Method using textual materials The details regarding the experimental procedure are given below

4.1.3.1

I'KE-I ES'I After selecting the schools for experimental study

invest~gatormade necessary arrangements with the schools for conducting experiments. The

heads of investigator

admlnlstered the Achievement test in Chemistry(Pre-test) to the Treatment Groups Remedial Teaching Group-RT(N=100), Self Learn~ng Group-SL(N=100) and Lecture Method Group-

LM(N=100) to assess the entry behaviour of the Educationally

Backward Students in Chemistry.

4.1.3.2

I-XPOSURE T O REMEDIAL TEACHING

The Group I (Remedial Teaching Group Remedial teaching

-

RT) was exposed to

by the investigator, using the Remedial

Teaching Materials in Chemistry prepared by the investigator. Facilities were provided to students to follow the procedures and learning situations given in Remedial Teaching Materials The previous knowledge of the students was assessed by suitable

activities and learning situations. Students were encouraged to develop terms, concepts and principles through discussion, observations, experiments, activities and projects. 4.1.3.7

FXPOSIJRE TO SELF-LEARNING

The Group II (Self Learning Group -SL) was exposed to self learning materials after assessing the entry behaviour

(Remedial Teaching Materials, prepared by the investigator for Remedial teaching Group, with necessary direction and

modification was used as self learning material)

4.1.3.4

E X P O S U R E TO LECTURE METHOD

T h e Group 111 (Lecture Method Group-LM) was exposed

to Lecture Method using the textual material. The experimental topics were taught by the investigator systematically with the help aids such as charts , models and of illustrations and audio v~sual

experiments At the end of each class, follow up activities were also glven

4.1.3.5.1 Immediate Post-test

The

investigator

administered

the

Achievement

test

in

Chemistry to the students in the Treatment Groups (RT, SL and

LM) immediately after the experimental teaching to assess the

terminal behaviour. (Same Achievement Test was used as Pretest and Immediate F'ost-test)

4.1.3.5.2

Delayed Memory Achievement

The Achievement test in Chemistry was administered to the students ot the Experrmental Groups after three months to assess the Delayed memory achievement. (The same

Achievement test in Chemistry was used as pre-test and delayed Memory Achievement test)

General

Data

sheet

were

also

administered

to

the

experimental Group along with Immediate Post-test .

-

-

-

--

-

Methodology

4.1.4

S'I'ATIS'TlCAL TECHNlQUES

The statistical techniques ernployed/adopted in the

present study are listed below:

(1)

Analysis of variance and analysis of co variance were used to study whether there is any significant difference among the Treatment Groups (RT, SL and LM) with regard to achievement in Chemistry

(2)

Test of significance of difference between percentages.

Methodology

-

REFERENCES

(1)

P . Tamir.(l971). An alternative approaclt to tlre corrstruction of t~ritltiple clroice test item, Journal

v01.5,pp.305-307. of Biological Education.

(2)

K.G.Tobion and W. Capie (1981 ). The development and validation

o f a groicp test of logical thinking. Educational and Psychological

Measurement Vol. 11,pp.413-424

(3)

D.F.Treagust(1986). Evaluating students' misconceptions by means

of'

diagriostic

multiple-clroice

items,

Research

in

Science

Education. Vol. 16, pp. 199-207. (4)

A.J. Lien. (1971). Measurement arrd Evaluation in Learning.

Lowa:William C. Brown company. (5)

J. K. Gilbert. (1977). The study of studerrt misutrderstarrdings irr

tlre pl~ysical scierrces,

pp.165-I71

Research in Science Education. Vo1.7,

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