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Elements

Group 16 Elements

The Chalcogens

All group elements are solids except oxygen oxygen, sulfur, and selenium = nonmetals tellurium = metalloid polonium = metal

Amanda Runge Meghan Estochen Mark Humberstone

Physical Properties

Selected Properties O Covalent radius/pm Ionic radius/pm First Ionization energy (kJ/mol) Melting point/ºC Boiling point/ºC Pauling Electronegative Electron Affinity (kJ/mol) 74 140 1310 -218 -183 3.5 141 S 104 184 1000 113 445 2.5 200 Se 117 198 941 217 685 2.4 195 Te 137 221 870 450 990 2.1 190 812 254 960 2 183 Po 140

OXYGEN

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OXYGEN

Oxygen, the most abundant element of the group, is found as two allotropes, dioxygen (O2) and ozone (O3). Dioxygen`s ground state is triplet oxygen as well as a state of higher energy, singlet oxygen.

Triplet State

OXYGEN

Singlet State

OXYGEN

Electrons and charged particles that are given off by the sun can hit triplet state oxygen, exciting it into the singlet state. When the electron falls back to the ground state, visible light is emitted, producing the Aurora Borealis. Colors seen are determined by the altitude and energy at which the collisions between particles and electrons are taking place Particles = 1000 ­ 15000 eV Occurs at poles because charged particles are channeled by Earth's magnetic field lines which go into the poles

OXYGEN

It is the second most electronegative element in periodic table, making it the most reactive of the group. The high electronegativity of oxygen leads to polarity in bonding.

i.e. Hydrogen-Bonding in water

The oxidation state of oxygen is -2. The lack of d-orbitals makes it difficult for higher states.

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SULFUR

SULFUR

Sulfur is commonly found as an 8-membered ring. Poor pi-orbital overlap due to larger atomic size hinders double bonding with itself. It can form stable compounds with oxidation states ranging between -2 and +6. Its most common states are -2, +4, and +6. This is due to the availability of d-orbitals.

SULFUR

Sulfur forms a similar structure with hydrogen as it does with oxygen, but the differences in electronegativity make H2S less polar and therefore less likely to hydrogen bond.

SULFUR

Sulfur was the basis for mustard gas, a cancer causing weapon used in World War I. By changing the structure of the gas and substituting nitrogen for sulfur, N-mustard is used to fight Hodgkin's Disease and many types of cancer. Sulfur is also a component found in stink bombs usually in the form of H2S.

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Mustard Gas

SULFUR

N-mustard

SELENIUM & TELLURIUM

Sulfur was the basis for mustard gas, a cancer causing weapon used in World War I. By changing the structure of the gas and substituting nitrogen for sulfur, N-mustard is used to fight Hodgkin's Disease and many types of cancer. Sulfur is also a component found in stink bombs usually in the form of H2S.

SELENIUM & TELLURIUM

Selenium and tellurium are both large metalloids with similar properties. They exhibit oxidation states similar to sulfur that also range from -2 to +6. Their commonly found structures are different. Selenium is found as an 8-membered ring (like sulfur) and tellurium crystallizes in a chain-like form.

SELENIUM & TELLURIUM

Selenium and tellurium combine with most elements although not as readily as the more electronegative members of the group, oxygen and sulfur. Selenium exhibits both photovoltaic and photoconductive actions and therefore is used in the production of photocells and solar cells.

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POLONIUM

POLONIUM

Polonium, a radioactive element, is rarely found in nature. It's made in small quantities by a nuclear reaction with bismuth. There are 29 known radioisotopes and more known isotopes than any other element.

209 83 1 Bi + 1n 210 84

Po + e-

POLONIUM

Polonium crystallizes in a cubic structure. Due to large atomic size, Pi orbital overlap becomes difficult, therefore rarely forms double bonds. Following the trend, it's the least electronegative of the group, yet combines directly with most elements.

POLONIUM

In November 2006, a 210 84 Po Russian spy named Alexander Litvinenko was poisoned with a lethal dose of 210Po. Less than a microgram was responsible for his death. Po decayed through alpha emission, heavily damaging vital organs.

206 82

Pb +

4 2

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SOURCES

Atkins and Shriver. Inorganic Chemistry. New York: W.H. Freeman and Company, 2006. Holland, Rebecca. "Molecule of the Month." Mustard Gas. Bristol University. 4/10/07 <http://www.bristol.ac.uk/Depts/Chemistry/MOT M/mustard/mustard.htm>. WebElementsTM, the periodic table on the WWW, URL: http://www.webelements.com/ Copyright 1993-2007 Mark Winter [The University of Sheffield and WebElements Ltd, UK]. All rights reserved. Document served: Tuesday 10th April, 2007

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