Explain the resonance structure of `CO_(2)` molecule?

Explanation

The single Lewis structure based on the presence of two singel bonds and one double bond between carbon and oxygen, atoms is inadequate to represent the molecule accurately as it represents unequal bonds. According to the experimental findings, all carbon to oxygen bonds in `CO _(3) ^(-2)` ion are equivelent. Therefore the carbonate ion is best described as a resonance hybrid of the canonical forms I, II and III shown below.

Resonance in `CO_(3) ^(2-).I,II and III`
represent the three cononical forms.