Functional groups are identified by specific arrangements of atoms within organic molecules that impart characteristic chemical properties. They are named based on the atoms they contain and their structural features. In organic chemistry, functional groups are often denoted by specific suffixes or prefixes in compound names. For example, the hydroxyl (-OH) functional group is identified by the suffix “-ol” in alcohols, while the carbonyl (C=O) group is denoted by the suffix “-one” in ketones. Additionally, functional groups can be identified through spectroscopic techniques such as infrared spectroscopy, which detects characteristic vibrational frequencies associated with specific functional groups.