nitrite vs chemical group

nitrite and chemical group both are nouns.

Word	Noun	Adjective	Verb	Adverb
nitrite	Yes	No	No	No
chemical group	Yes	No	No	No

As nouns, chemical group is a hypernym of nitrite; that is, chemical group is a word with a broader meaning than nitrite:

nitrite: the radical -NO2 or any compound containing it (such as a salt or ester of nitrous acid)
chemical group: (chemistry) two or more atoms bound together as a single unit and forming part of a molecule

Other hypernyms of nitrite include group, radical.

nitrite (noun)	chemical group (noun)
the radical -NO2 or any compound containing it (such as a salt or ester of nitrous acid)	(chemistry) two or more atoms bound together as a single unit and forming part of a molecule