Any of the elements in Group 16 of the periodic table (oxygen, sulfur, selenium, tellurium, and polonium), which readily form negative ions.
From Greek 'chalkos' (copper) and '-gen' (producer), because early chemists noticed these elements combined readily with copper to form important minerals and compounds.
The chalcogens are chemistry's generalists—they bond with nearly every element on the periodic table, which is why they appear in thousands of minerals and compounds. Oxygen alone (a chalcogen) makes up 20% of Earth's atmosphere.
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