1 Like
Thank you for the suggestion.
I believe the carbonate ion has conjugation. The central carbon and all three oxygens are sp²-hybridized, each possessing an unhybridized p orbital that can overlap side-by-side. This continuous overlap creates a conjugated π system across the entire ion, allowing the π electrons and lone pairs on the oxygens to delocalize. Feel free to resubmit if you have an MCAT specific source citation to suggest otherwise though.