The carbon atom of the carbonyl group is

The correct answer is Option (1) → sp² hybridized

The hybridisation of a carbon atom follows from the number of σ bonds it forms: four σ bonds need sp³, three need sp² and two need sp.

The carbonyl carbon forms three σ bonds: one to oxygen and two to other carbon or hydrogen atoms. So it is sp² hybridised. These three bonds lie in one plane at about 120°, so the carbonyl group is trigonal planar. The unhybridised p orbital of carbon overlaps with a p orbital of oxygen to form the π bond of C=O.

Because oxygen is more electronegative, the C=O bond is polar: the carbon is electron-deficient (electrophilic) and the oxygen is electron-rich.

NCERT (2026-27 edition):
Structure of the Carbonyl Group