ABSTRACT
Chemical properties Cobalt can display three oxidation states, +3, +2, and +1; the latter is extremely unstable but nevertheless is important in biology. Cobalt is generally found in the form of ores with arsenic or arsenic and sulfur. However, when pure the metal has a bluish-white color and is quite hard, with a melting point of 1490∞C. It is a relatively unreactive element, not readily attacked by air and only oxidized by oxygen at high temperatures. As the +2
oxidation state is the most stable, cobalt (II) compounds are the most common. Cobalt (II) will complex with ammonia and cyanide ions, for example, in solution but on doing so is readily oxidized to Co(III) by these ligands.
