Pen"tad (?), n. [Gr. , , a body of five, fr. five.] Chem.
Any element, atom, or radical, having a valence of five, or which can be combined with, substituted for, or compared with, five atoms of hydrogen or other monad; as, nitrogen is a pentad in the ammonium compounds.
© Webster 1913.
Pen"tad, a. Chem.
Having the valence of a pentad.
© Webster 1913.