monoatomic atom definition
monatomic. adj. 1. (Chemistry) (of an element) having or consisting of single atoms: argon is a monatomic gas. 2. (Chemistry) (of a compound or molecule) having only one atom or group that can be replaced in a chemical reaction. 3. (Chemistry) a less common word for monovalent. (ËmÉn ÉËtÉm Éªk). adj.