Common elements with two oxidation states in cations Fe II iron (II) ferrous Fe III iron (III) ferric Cu I copper (I) cuprous Cu II copper (II) cupric Hg I mercury (I) mercurous Hg II mercury (II) mercuric Au I gold (I) Au III gold (III) Sn II tin (II) stannous Sn IV tin (IV) stannic Tl I thallium (I) Tl III thallium (III) Pb II lead (II) plumbous Pb IV lead (IV) plumbic