What term describes a group of atoms responsible for the characteristic reactions of a compound?

• A. Molecule
• B. Functional group
• C. Ion
• D. Element

Answer: (B)

The idea being tested is that the reactive behavior of a compound is governed by specific substructures within the molecule. Those substructures are called functional groups, groups of atoms that determine how the molecule behaves in reactions. For example, a carbonyl or hydroxyl group imparts characteristic reactivity, influencing how the molecule interacts with other reagents. A molecule is any bound collection of atoms, which may contain functional groups, but it does not by itself name the reactive portion. An ion is a charged particle, and an element is a pure substance of one type of atom; neither describes the part of a molecule that controls its typical reactions. Therefore, the best description for the group of atoms responsible for the characteristic reactions of a compound is functional group.