Chalcogen

Chalcogen is the name for the elements of Group 16 (VIA) of the periodic table: oxygen, sulfur, selenium, tellurium, polonium, and livermorium. The term comes from Greek chalcos (ore) and genes, reflecting their association with ore deposits and the formation of chalcogenide compounds. They generally have six valence electrons and show oxidation states from -2 to +6, with oxygen the most reactive and the heavier members less so.

Chemically, chalcogens include nonmetals (oxygen, sulfur, selenium) and metalloids or metals (tellurium, polonium, livermorium). They form oxides, sulfides and selenides, and can form hydrogen chalcogenides such as H2O, H2S, H2Se and H2Te. Reactivity and metallic character increase down the group; polonium and livermorium are radioactive and have limited practical chemistry.

Occurrence and uses: Oxygen accounts for about 21% of Earth's atmosphere and is abundant in rocks; sulfur is common in minerals and fuels. Selenium and tellurium occur in trace minerals and have niche applications in electronics and alloys. Polonium is extremely rare and radioactive; livermorium has no practical applications outside research. Industry relies on sulfuric acid production, combustion with oxygen, and electronics using selenium or tellurium.

Biological role: Oxygen is essential for aerobic respiration; sulfur is a component of certain amino acids and vitamins. Collectively, chalcogens play pivotal roles in chemistry, geology, industry, and biology.