Nickel is a transition metal that forms two common ions, Ni(II) and Ni(III). Ni(II) is more stable and is the most common oxidation state of nickel. It has a charge of +2 and is found in compounds such as nickel(II) oxide (NiO) and nickel(II) chloride (NiCl2). Ni(III) is less stable and is found in compounds such as nickel(III) oxide (Ni2O3) and nickel(III) chloride (NiCl3).
