Which of the following statements correctly describes the Lewis dot structure of the carbonate ion, CO_3^{2-}?

• A. It contains a central carbon atom bonded to two oxygen atoms and one hydrogen atom.
• B. It contains a central carbon atom bonded to three oxygen atoms, with two double bonds and one single bond.
• C. It has three equivalent resonance structures, each with one double bond and two single bonds to oxygen atoms.
• D. It has a central carbon atom bonded to three oxygen atoms, with all bonds being single bonds.

Answer: (C)

Verified step by step guidance

1. Step 1: Identify the atoms and total valence electrons in the carbonate ion, CO_3^{2-}. Carbon has 4 valence electrons, each oxygen has 6 valence electrons, and the 2- charge adds 2 extra electrons. Calculate the total number of valence electrons to be used in the Lewis structure.
2. Step 2: Arrange the atoms with carbon as the central atom bonded to three oxygen atoms, since carbon typically forms four bonds and oxygen usually forms two bonds.
3. Step 3: Draw single bonds between the carbon and each oxygen atom, then distribute the remaining electrons to satisfy the octet rule for each oxygen atom, placing lone pairs as needed.
4. Step 4: To satisfy the octet rule for carbon, form double bonds by converting lone pairs on oxygen atoms into bonding pairs. Because the carbonate ion has resonance, consider that the double bond can be placed between carbon and any one of the three oxygens, resulting in three equivalent resonance structures.
5. Step 5: Recognize that the correct Lewis structure for CO_3^{2-} is a resonance hybrid of three structures, each with one C=O double bond and two C–O single bonds, with the negative charges delocalized over the oxygen atoms.