Q.Draw the resonance structures of the carbonate ion, $\text{CO}_3^{2-}$, and explain why all three carbon–oxygen bonds are found experimentally to have the same, intermediate bond length.

[!TLDR] $\text{CO}_3^{2-}$ has three equivalent resonance structures, each with the C=O double bond on a different oxygen. [!ANSWER] Because the real ion is a resonance hybrid of all three structures, the double-bond character (and hence bond length) is eve …

A single Lewis structure for $\text{CO}_3^{2-}$ places a $\text{C}=\text{O}$ double bond on one specific oxygen and single $\text{C}-\text{O}^-$ bonds on the other two — but there is nothing chemically special about any one of the three oxygens, so two further, entirely equivalent structures exist, each with the double bond shifted to a different oxygen. These three structures differ only in electron placement, not in the positions of the atoms, which is the defining condition for resonance. The real carbonate ion is not any single one of these three structures, nor does it flip between them over time; it is a single, static resonance hybrid in which the double-bond character is delocalised evenly across all three C–O bonds simultaneously, each bond carrying roughly one-third double-bond character and two-thirds single-bond character. Consequently, all three C–O bond lengths come out experimentally identical, at an intermediate value (about $128\ \text{pm}$) between a pure C–O single bond ($143\ \text{pm}$) an …

Draw the three equivalent resonance structures, explain that the real species is their hybrid (not an oscillation), and connect this to t …

Describing the ion as rapidly switching between the three structures over time, rather than being …