Which polyatomic ion has a charge of 3–?

• A. Nitrate (NO_3^{-})
• B. Sulfate (SO_4^{2-})
• C. Phosphate (PO_4^{3-})
• D. Carbonate (CO_3^{2-})

Answer: (C)

Verified step by step guidance

1. Review the charges of common polyatomic ions to understand their typical charges.
2. Recall that nitrate (NO_3) has a charge of 1–, written as \(NO_3^{1-}\) or simply \(NO_3^{-}\).
3. Recognize that sulfate (SO_4) and carbonate (CO_3) both have charges of 2–, written as \(SO_4^{2-}\) and \(CO_3^{2-}\) respectively.
4. Identify that phosphate (PO_4) is the polyatomic ion with a charge of 3–, written as \(PO_4^{3-}\).
5. Conclude that among the given options, phosphate is the ion with a 3– charge.