Chemical formula for cuprite is Cu₂O. Copper has oxidation number +1 and oxygen has -2 (2·(+1) + (-2) = 0). Chemical formula for chalcocite is Cu₂S. Copper has oxidation number +1 and sulfur has -2 (2·(+1) + (-2) = 0). Chemical formula for covellite is CuS. Copper has oxidation number +2 and sulfur has -2.
