cation, atom or group of atoms carrying a positive charge. The charge results because there are more protons than electrons in the cation. Cations can be formed from a metal by oxidation (see oxidation and reduction), from a neutral base (see acids and bases) by protonation, or from a polar compound by ionization. Cationic species include Na⁺, Mg⁺⁺, and NH₄⁺. The cations of the transition elements have characteristic colors in water solution. Salts are made up of cations and anions. See ion.