pentavalent vs valence

pentavalent is not a noun while valence is a noun.

Word	Noun	Adjective	Verb	Adverb
pentavalent	No	Yes	No	No
valence	Yes	No	No	No

pentavalent (noun)	valence (noun)
	(chemistry) a property of atoms or radicals; their combining power given in terms of the number of hydrogen atoms (or the equivalent)
	(biology) a relative capacity to unite or react or interact as with antigens or a biological substrate

pentavalent (adjective)	valence (adjective)
having a valence of five