Final answer:
An aldehyde contains the -CHO group which is characterized by a carbon atom bonded to a hydrogen and a carbonyl group (C=O). This functional group is key in organic chemistry for its reactivity and properties.
Step-by-step explanation:
The functional group found in an aldehyde is the -CHO group, which is a form of the carbonyl group. An aldehyde's structure consists of a carbon atom double-bonded to an oxygen atom (forming the carbonyl) and single-bonded to at least one hydrogen atom. This can be represented as R-C2O, where R can be either a hydrogen atom or a hydrocarbon group. The presence of the hydrogen atom distinguishes aldehydes from ketones, which have two carbon groups attached to the carbonyl carbon atom instead. Functional groups like aldehydes play a vital role in organic chemistry as they largely determine the chemical reactivity and properties of molecules.