ammonium ion vs ammonium

ammonium ion and ammonium both are nouns.

Word	Noun	Adjective	Verb	Adverb
ammonium ion	Yes	No	No	No
ammonium	Yes	No	No	No

As nouns, ammonium ion and ammonium are synonyms defined as:

ammonium ion and ammonium: the ion NH4 derived from ammonia; behaves in many respects like an alkali metal ion

ammonium ion (noun)	ammonium (noun)
the ion NH4 derived from ammonia; behaves in many respects like an alkali metal ion	the ion NH4 derived from ammonia; behaves in many respects like an alkali metal ion