Which of the following is the formula for the polyatomic ion called carbonate?

• A. CO_3^{2-}
• B. PO_4^{3-}
• C. SO_4^{2-}
• D. NO_3^{-}

Answer: (A)

Verified step by step guidance

1. Understand that a polyatomic ion is a charged species composed of two or more atoms covalently bonded together, carrying an overall charge.
2. Recall the common polyatomic ions and their formulas: carbonate, phosphate, sulfate, and nitrate are among the most common.
3. Identify the carbonate ion, which consists of one carbon atom and three oxygen atoms, carrying a charge of 2-.
4. Write the formula for carbonate as \(C\!O_3^{2-}\), where the subscript 3 indicates three oxygen atoms and the superscript 2- indicates the charge.
5. Compare this formula to the other options: phosphate (\(P\!O_4^{3-}\)), sulfate (\(S\!O_4^{2-}\)), and nitrate (\(N\!O_3^{-}\)) to confirm that \(C\!O_3^{2-}\) is the correct formula for carbonate.