In the carbonyl group, carbon atom is in a state of $\text{s}{\text{p}}^2$ hybridisation. One $\text{s}{\text{p}}^2$ hybrid orbital overlap with a unhydridised $\text{p}$-orbital of oxygen to form $\mathrm{\text{C}}-\mathrm{\text{O}}$ $\text{σ}$-bonds. The remaining two $\text{s}{\text{p}}^2$ orbitals of carbon form $\text{σ}$-bonds with $\text{s}$-orbitals of hydrogen or $\text{s}{\text{p}}^3$-orbitals of carbon of the alkyl groups. The $\mathrm{\text{C}}-\mathrm{\text{O}}$ $\text{π}$-bond is formed by the sideways overlap of $\text{p}$-orbitals of carbon and oxygen. Thus, the three $\text{σ}$-bonds of carbonyl carbon lie in one plane and are $120°$ aprat