Aldehydes and ketones are two of the most common types of carbonyl groups. Aldehydes are characterized by the presence of a carbonyl group at the end of a carbon chain, while ketones have the carbonyl group in the middle of the carbon chain. Some common examples of aldehydes include formaldehyde, acetaldehyde, and benzaldehyde. Some common examples of ketones include acetone, butanone, and cyclohexanone.