Answer:
In terms of central atom carbon:
three sp2 hybridized orbitals
one "2p" orbital.
one sp2 hybridized orbital and one "2p" orbital bonds with oxygen atom.
Explanation:
In acetaldehyde we have two carbons.
One carbon is simple alkyl carbon
The other carbon is carbonyl carbon
The carbonyl carbon is bonded to the alkyl carbon and hydrogen by sigma bonds (one with each) and to the oxygen atom by one sigma and one pi bond.Which means that there are three sigma bonds and one pi bond.
The hybridisation of carbonyl carbon is sp2.
The atomic orbitals involved are:
three "2p" orbitals
one "2s" orbital
Out of the three "2p" orbitals : two are involved in hybridization.
The third one is showing side ways overlapping with the "2p" orbital of oxygen atom.