Explain why $CO_3^{2-}$ ion cannot be represented by a single Lewis structure. How can it be best represented?

(N/A) single Lewis structure of $CO_3^{2-}$ ion cannot explain all the properties of this ion.
If it were represented by only one structure,there should be two types of bonds,i.e.,one $C=O$ double bond and two $C-O$ single bonds. However,experimental evidence shows that all three $C-O$ bonds are identical in bond length and bond strength.
Therefore,it is best represented as a resonance hybrid of three canonical structures as shown below:
$(i)$ $\leftrightarrow$ (ii) $\leftrightarrow$ (iii) $\equiv$ Resonance hybrid