Which of the following polyatomic ions has a 2- charge?

• A. Phosphate (PO_4^{3-})
• B. Ammonium (NH_4^{+})
• C. Sulfate (SO_4^{2-})
• D. Nitrate (NO_3^{-})

Answer: (C)

Verified step by step guidance

1. Review the charges of each polyatomic ion given in the problem: Phosphate (PO_4^{3-}), Ammonium (NH_4^{+}), Sulfate (SO_4^{2-}), and Nitrate (NO_3^{-}).
2. Recall that the charge on a polyatomic ion is indicated by the superscript number and sign, such as 3- for phosphate, + for ammonium, 2- for sulfate, and 1- for nitrate.
3. Identify which ion has a charge of 2- by comparing the charges: look for the ion with the superscript \(^{2-}\).
4. Confirm that sulfate (SO_4^{2-}) is the ion with a 2- charge, as indicated by its formula.
5. Understand that the charge on polyatomic ions is important for balancing chemical equations and forming neutral compounds.