nitro group vs chemical group

nitro group and chemical group both are nouns.

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

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

nitro group: the group -NO3
chemical group: (chemistry) two or more atoms bound together as a single unit and forming part of a molecule

Other hypernyms of nitro group include group, radical.

nitro group (noun)	chemical group (noun)
the group -NO3	(chemistry) two or more atoms bound together as a single unit and forming part of a molecule