monatomic vs monoatomic

monatomic and monoatomic both are adjectives.

Word	Noun	Adjective	Verb	Adverb
monatomic	No	Yes	No	No
monoatomic	No	Yes	No	No

As adjectives, monatomic and monoatomic are synonyms defined as:

monatomic and monoatomic: of or relating to an element consisting of a single atom

monatomic (adjective)	monoatomic (adjective)
of or relating to an element consisting of a single atom	of or relating to an element consisting of a single atom