The polyatomic ion carbonate, CO32−, is a frequently cited example of delocalized bonding.
Consider the carbonate ion in isolation, in the gas phase.
(a) Draw all valid Lewis structures for CO32− that satisfy the octet rule for all atoms. Show all lone-pair electrons and indicate formal charges on every atom in each structure.
(b) For ONE of the structures you drew in part (a), calculate the formal charge on the carbon atom and on each oxygen atom, showing your reasoning.
(c) Treating the structures you drew in part (a) as equivalent contributors to the resonance hybrid, determine the average bond order for a C–O bond in CO32−. Show your calculation.
(d) Explain how the bond order you obtained in part (c) accounts for the fact that all three C–O bond lengths in CO32− are experimentally found to be identical and shorter than a typical C–O single bond but longer than a C=O double bond.