What are the different types of functional groups?

One type of functional group is the hydroxyl group (-OH). It exists in alcohols and phenols and consists of an oxygen atom bonded to a hydrogen atom. Another type is the amino group (-NH2). These groups exist in amines and amino acids, and consist of a nitrogen atom bonded to two hydrogen atoms; it acts as a base and can form hydrogen bonds. Carboxyl group (-COOH) is another type. It is present in carboxylic acids and includes a carbonyl group and a hydroxyl group attached to the same carbon atom. Ketone group (R-CO-R') is another type. It is a carbonyl group where the carbonyl carbon is bonded to two alkyl or aryl groups. Nitrate groups (-NO3) include a nitrogen atom bonded to three oxygen atoms. Another type is aldehyde group (-CHO), which is a carbonyl group with at least one hydrogen atom attached to the carbonyl carbon.