• (adj): Having a valence of five.

Some articles on pentavalent:

Pentavalent Antimonial
... Pentavalent antimonials (also abbreviated pentavalent Sb or SbV) are a group of compounds used for the treatment of leishmaniasis ... They are also called pentavalent antimony compounds ...
Arsenic Toxicity - Kinetics
... inorganic arsenic, reduced (trivalent As (III)) and oxidized (pentavalent As(V)), can be absorbed, and accumulated in tissues and body fluids ... be a detoxification if "As intermediates are not permitted to accumulate" because the pentavalent organoarsenics have a lower affinity to thiol groups than inorganic pentavalent arsenics ...