The Collaborative International Dictionary
Tetratomic
Tetratomic \Tet`ra*tom"ic\, a. [Tetra- + atomic.] (Chem.)
Consisting of four atoms; having four atoms in the molecule, as phosphorus and arsenic.
Having a valence of four; quadrivalent; tetravalent; sometimes, in a specific sense, having four hydroxyl groups, whether acid or basic.
Wiktionary
tetratomic
a. (context chemistry of a molecule etc English) consisting of four atoms