All the $C-O$ bonds in carbonate ion $(CO_3^{2-})$ are equal in length. Explain.

(N/A) The carbonate ion $(CO_3^{2-})$ has a trigonal planar geometry.
According to the concept of resonance, the actual structure of the carbonate ion is a resonance hybrid of three canonical structures.
In these structures, the double bond is delocalized over all three $C-O$ bonds.
As a result, each $C-O$ bond possesses a partial double bond character, making all three $C-O$ bond lengths equal (approximately $128 \text{ pm}$).