multivalence vs multivalency

multivalence and multivalency both are nouns.

Word	Noun	Adjective	Verb	Adverb
multivalence	Yes	No	No	No
multivalency	Yes	No	No	No

As nouns, multivalence and multivalency are synonyms defined as:

multivalence and multivalency: (chemistry) the state of having a valence greater than two

Other synonyms of multivalence include polyvalence, polyvalency.

multivalence (noun)	multivalency (noun)
(chemistry) the state of having a valence greater than two	(chemistry) the state of having a valence greater than two