Chalcogen

The chalcogens are the elements in column 16 (or group VI A in the old notation) of the periodic table of elements :oxygen, sulphur, selenium, tellurium and polonium.

Their outer shell has a deficit of two electrons, hence their propensity to form two bonds or a double bond, for example in the molecule H₂O and the CO group (in the acidic function of an organic molecule). They also occur in the form of negative ions when they have captured the two missing electrons.

The term chalcogen means Which gives copper. Chemically, there is no direct relationship with this metal, but the main copper ores are compounds that include a chalcogen, such as copper oxide for example.