chemist vs Richard John Roberts

chemist and Richard John Roberts both are nouns.

Word	Noun	Adjective	Verb	Adverb
chemist	Yes	No	No	No
Richard John Roberts	Yes	No	No	No

chemist (noun)	Richard John Roberts (noun)
a scientist who specializes in chemistry	United States biochemist (born in England) honored for his discovery that some genes contain introns (born in 1943)
a health professional trained in the art of preparing and dispensing drugs