The CO₃²⁻ ion, commonly known as the carbonate ion, consists of one carbon atom and three oxygen atoms. Within this ion, the bonding between the carbon and oxygen atoms is best described as resonance, which involves both single and double bonds.
In a simplified representation of the carbonate ion, one oxygen atom is connected to the carbon atom with a double bond, while the other two oxygen atoms are connected with single bonds. However, the actual structure of the CO₃²⁻ ion is a hybrid of these representations due to resonance. This means that, in practice, each carbon-oxygen bond is neither purely single nor purely double, but has characteristics of both.
Because of this resonance, the bond lengths and strengths are averaged out, leading to bonds that are intermediate in nature. Thus, it’s accurate to say that while the carbon-oxygen bonds include features of both single and double bonds, they are best understood through the concept of resonance, which results in equivalent bond characteristics across all three bonds in the ion.