What functional group is characterized by a carbon atom bonded to a nitrogen atom and a carbon atom?

The correct answer is that the functional group characterized by a carbon atom bonded to a nitrogen atom and a carbon atom is an amide. An amide consists of a carbonyl group (a carbon atom double-bonded to an oxygen atom) directly attached to a nitrogen atom, which in turn is connected to another carbon atom. This structure defines amides, and they are represented by the general formula R1R2N-C(=O)-R3, where R1 and R2 can be hydrogen or hydrocarbon groups, and R3 is a hydrocarbon group or hydrogen.

In contrast, an aldehyde features a carbon atom bonded to a hydrogen atom and a carbonyl group (C=O), without any nitrogen atoms involved. Similarly, a carboxylic acid contains a carbon atom bonded to both a hydroxyl group (-OH) and a carbonyl group, which again does not include a nitrogen atom. Lastly, while amines do involve nitrogen bonded to carbon, they do not have the carbonyl functional group present. Thus, the presence of both the carbonyl group and nitrogen in amides distinguishes them as the correct answer in this context.