All the C−O bonds in carbonate ion (CO2−3) are equal in length. Explain.
Definition of resonance and resonating structure
Resonance: Resonance is a way of describing delocalized electrons within certain molecules or polyatomic ions where the bonding cannot be expressed by a single Lewis structure.
Resonating structure: These structures are sets of Lewis structures that describe the delocalization of electrons in a polyatomic ion or a molecule. The skeleton of the structure can not be changed (only the electrons move) and number of electrons should remain same in these structures.
So, the actual structure of the molecule is given by contribution from all of these resonating structure and the structure formed is called as resonance hybrid.
Since all three resonating structures are equivalent and the actual structure of the molecule is given by their resonance hybrid and from the resonance hybrid, it is clearly visible that all three C−O bonds have the same bond length in carbonate ion.