monatomic

Occurring as single atoms.

Having the same valence or atomicity as hydrogen, represented by unity.

Consisting of, or containing, one atom.

Having the equivalence or replacing power of an atom of hydrogen; univalent.

Of an element, consisting of a single atom in the molecule; for example: the noble gases. Note: strictly speaking, a molecule has at least two atoms.

of or relating to an element consisting of a single atom