The alkali metals in group 1 are always +1 when they form cations. The alkaline earth metals in group 2 are always +2 when they form cations. Aluminum and the elements in group 3 are always +3 when they form cations. Zinc and cadmium always form +2 cations. Monatomic Cation Names. The names of monatomic cations always start with the name of the metal, sometimes followed by a Roman numeral to indicate the charge of the ion. For example, Cu + is copper(I), and Cu 2+ is copper(II).