monatomic

adjective Chemistry.

1. having one atom in the molecule.
2. containing one replaceable atom or group.
3. having a valence of one.

adjective chem

1. (of an element) having or consisting of single atomsargon is a monatomic gas
2. (of a compound or molecule) having only one atom or group that can be replaced in a chemical reaction
3. a less common word for monovalent

adj.

1. Occurring as single atoms.
2. Having one replaceable atom or radical.
3. Univalent.