A chemical element, symbol Sn, atomic number 50, atomic weight 118.69. Tin forms tin(II) or stannous (Sn²⁺), and tin(IV) or stannic (Sn⁴⁺) compounds, as well as complex salts of the stannite (M₂SnX₄) and stannate (M₂SnX₆) types.