According to picture below, p atomic <span>orbitals overlap are responsible for the π bond between carbon and oxygen.
Both carbon and oxygen have sp2 hybridization in this carbonyl group. Carbon has three sigma bonds with sp2 orbitals and oxygen has one sigma bond with sp2 and two free electron pairs with sp2 orbitals. Pi bonds are formed between two p orbitals.</span>
Both carbon and oxygen have sp2 hybridization in this carbonyl group. Carbon has three sigma bonds with sp2 orbitals and oxygen has one sigma bond with sp2 and two free electron pairs with sp2 orbitals. Pi bonds are formed between two p orbitals.</span>