 Common oxidation states of cobalt include + 2 and + 3 , although compounds with oxidation states ranging from − 3 to + 4 are also known . A common oxidation state for simple compounds is + 2 ( cobalt ( II ) ) . These salts form the pink @-@ colored metal aquo complex [ Co ( H2O ) 6 ] 2 + in water . Addition of chloride gives the intensely blue [ CoCl 
