atomic number 20 vs burnt lime

atomic number 20 and burnt lime both are nouns.

Word	Noun	Adjective	Verb	Adverb
atomic number 20	Yes	No	No	No
burnt lime	Yes	No	No	No

atomic number 20 (noun)	burnt lime (noun)
a white metallic element that burns with a brilliant light; the fifth most abundant element in the earth's crust; an important component of most plants and animals	a white crystalline oxide used in the production of calcium hydroxide