Which of the following statements correctly describes the resonance structures of the acetate ion, CH3COO-?

• A. The resonance involves the hydrogen atoms of the methyl group.
• B. The negative charge is delocalized equally over both oxygen atoms.
• C. There is no resonance; the negative charge is fixed on one oxygen atom.
• D. The negative charge is localized only on the carbon atom.

Answer: (B)

Verified step by step guidance

1. Understand that resonance structures are different Lewis structures for the same molecule that show the delocalization of electrons, typically involving pi bonds or lone pairs, without changing the positions of atoms.
2. Identify the acetate ion (CH3COO-) structure: it has a methyl group (CH3-) attached to a carboxylate group (COO-), where the negative charge is associated with the oxygen atoms in the carboxylate group.
3. Recognize that resonance in the acetate ion involves the two oxygen atoms in the carboxylate group sharing the negative charge through the delocalization of electrons, not involving the hydrogen atoms of the methyl group or the carbon atom.
4. Recall that resonance structures for acetate show the negative charge equally distributed over both oxygen atoms, which stabilizes the ion by spreading out the charge.
5. Conclude that the correct description is that the negative charge is delocalized equally over both oxygen atoms, and the other options are incorrect because they either involve incorrect atoms or deny the presence of resonance.