Which of the following represents the carbonate ion?

Which of the following represents the carbonate ion?

• A. Nitrate
• B. Carbonate
• C. Sulfate
• D. Ammonium

Answer: (B)

Carbonate is the oxyanion with the formula CO3^2-. It has a central carbon bonded to three oxygens and carries a -2 overall charge. In its Lewis structure, the charge is delocalized over the three C–O bonds through resonance, so each C–O bond has partial double-bond character and the ion is trigonal planar around carbon (about 120° angles). Recognizing carbonate means spotting CO3^2− as the ion with three oxygens and a -2 charge. The other ions listed—nitrate (NO3^-), sulfate (SO4^2-), and ammonium (NH4^+)—have different central atoms, numbers of oxygens, or charges.

Carbonate is the oxyanion with the formula CO3^2-. It has a central carbon bonded to three oxygens and carries a -2 overall charge. In its Lewis structure, the charge is delocalized over the three C–O bonds through resonance, so each C–O bond has partial double-bond character and the ion is trigonal planar around carbon (about 120° angles). Recognizing carbonate means spotting CO3^2− as the ion with three oxygens and a -2 charge. The other ions listed—nitrate (NO3^-), sulfate (SO4^2-), and ammonium (NH4^+)—have different central atoms, numbers of oxygens, or charges.