## Chemistry: Principles and Practice (3rd Edition)

(a) K$^{1+}$ (b) Br$^{1-}$ (c) Ba$^{2+}$ (d) S$^{2-}$
(a) K$^{1+}$ The elemental symbol for potassium is K. Potassium is in group 1; therefore, it has a valence of 1+. (b) Br$^{1-}$ The elemental symbol for bromine is Br. Bromine is in group 17; therefore, it has a valence of 1-. (c) Ba$^{2+}$ The elemental symbol for barium is Ba. Barium is in group 2; therefore, it has a valence of 2+. (d) S$^{2-}$ The elemental symbol for sulfur is S. Sulfur is in group 16; therefore, it has a valence of 2-.