Group 16 elements have 6 valence electrons, meaning that they require two more electrons to complete a stable electron octet. They still have relatively large electron affinities and are rather reactive, forming ions with a -2 charge. All but polonium form volatile compounds with hydrogen: water H2O, hydrogen sulfide H2S, hydrogen selenide H2Se, and hydrogen telluride H2Te.
Electronegativity decreases in this group with increasing atomic mass, and oxygen is more electronegative than any element except fluorine; it acts much like a halogen except for its -2 oxidation state. Fluorine and oxygen oxidize these elements (except oxygen) to the +6 oxidation state, resulting in such substances (for sulfur) as sulfur hexafluoride SF6 and sulfur trioxide SO3 and its derivative sulfuric acid H2SO4, one of the most heavily-used industrial chemicals. (Note that use of sulfuric acid requires extreme care because it causes chemical burns upon flesh, cloth, and paper). Typically, these elements will attain an oxidation state of -2.
Oxides of sulfur, selenium, and tellurium are acidic. Strong radioactivity largely masks the chemical properties of polonium..........
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