Which of the following best represents the resonance hybrid of the carbonate ion, CO_3^{2-}?

• A. A structure with alternating single and double bonds and localized negative charges on two oxygen atoms.
• B. A structure with one double bond and two single bonds between carbon and oxygen atoms.
• C. A structure with two double bonds and one single bond between carbon and oxygen atoms.
• D. A structure with all three C–O bonds shown as identical, with partial double-bond character and delocalized negative charge.

Answer: (D)

Verified step by step guidance

1. Understand that resonance structures are different Lewis structures for the same molecule that differ only in the placement of electrons, not atoms.
2. Recognize that the carbonate ion, CO_3^{2-}, has three oxygen atoms bonded to a central carbon atom, and the overall charge is -2.
3. Draw the possible resonance structures showing alternating single and double bonds between carbon and oxygen, with negative charges localized on some oxygen atoms.
4. Realize that the actual structure of the carbonate ion is a resonance hybrid, meaning the true bonding is a blend of all resonance forms, resulting in bonds that are equivalent and have partial double-bond character.
5. Conclude that the best representation of the resonance hybrid shows all three C–O bonds as identical with delocalized negative charge spread evenly over the oxygen atoms, rather than localized single or double bonds.