Which ion would bond with a calcium ion (Ca^{2+}) to form a neutral ionic compound?

• A. PO_4^{3-}
• B. Cl^{-}
• C. NO_3^{-}
• D. SO_4^{2-}

Answer: (D)

Verified step by step guidance

1. Identify the charge on the calcium ion, which is given as \(\mathrm{Ca^{2+}}\), meaning it has a +2 charge.
2. Look at the charges on the possible anions: \(\mathrm{PO_4^{3-}}\) has a -3 charge, \(\mathrm{Cl^{-}}\) has a -1 charge, \(\mathrm{NO_3^{-}}\) has a -1 charge, and \(\mathrm{SO_4^{2-}}\) has a -2 charge.
3. To form a neutral ionic compound, the total positive charge must balance the total negative charge. Since calcium has a +2 charge, it will most simply balance with an ion that has a -2 charge.
4. Compare the charges: \(\mathrm{SO_4^{2-}}\) has a -2 charge, which perfectly balances the +2 charge of \(\mathrm{Ca^{2+}}\) in a 1:1 ratio, resulting in a neutral compound.
5. Therefore, the ion that bonds with \(\mathrm{Ca^{2+}}\) to form a neutral ionic compound is \(\mathrm{SO_4^{2-}}\).