functional group

A functional group is a specific cluster of atoms within a molecule that determines how the molecule behaves and reacts chemically. Think of it as a "choose your own adventure" part of a molecule that influences its properties, like acidity, solubility, or reactivity. For example, the hydroxyl group (–OH) found in alcohols affects how alcohols interact with water. These groups are consistent across different molecules, allowing chemists to predict and understand their chemical behavior based on the presence of specific functional groups.