## Chemistry: The Molecular Science (5th Edition)

One $Ca^{2+}$ ion and one $SO_{3}^{2-}$ ion.
Calcium is a group 2A element and therefore forms a 2+ ion. Sulfite is a polyatomic ion with 2- charge. One $Ca^{2+}$ ion balances the 2- charge of the Sulfite $(SO_{3}^{2-})$.