When an oxygen atom forms a double bond to a carbon atom, a carbonyl functional group is obtained.In a ketone, both atoms bonded to the carbonyl carbon are other carbon atoms, and, in an aldehyde, at least one atom on the carbonyl carbon is a hydrogen.A wide range of functional groups are produced by the presence of different atomic groupings on the carbon of the carbonyl group.The carbon atom of a carbonyl group is bonded to two other atoms in addition to the oxygen atom.bond.