Which of the following polyatomic ions has a positive charge?

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

Answer: (C)

Verified step by step guidance

1. Review the charges on each polyatomic ion given in the problem: Phosphate (PO_4^{3-}), Nitrate (NO_3^-), Ammonium (NH_4^+), and Sulfate (SO_4^{2-}).
2. Recall that most common polyatomic ions carry a negative charge, which is indicated by the superscript minus signs (e.g., 3-, 2-, or 1-).
3. Identify the ion with a positive charge by looking for a superscript plus sign (+) in its formula.
4. Note that Ammonium (NH_4^+) is the only polyatomic ion listed with a positive charge, as indicated by the superscript plus sign.
5. Conclude that Ammonium is the polyatomic ion with a positive charge, while the others are negatively charged ions.