scandium vs atomic number 21

scandium and atomic number 21 both are nouns.

Word	Noun	Adjective	Verb	Adverb
scandium	Yes	No	No	No
atomic number 21	Yes	No	No	No

As nouns, scandium and atomic number 21 are synonyms defined as:

scandium and atomic number 21: a white trivalent metallic element; sometimes classified in the rare earth group; occurs in the Scandinavian mineral thortveitite

Other synonyms of scandium include Sc.

scandium (noun)	atomic number 21 (noun)
a white trivalent metallic element; sometimes classified in the rare earth group; occurs in the Scandinavian mineral thortveitite	a white trivalent metallic element; sometimes classified in the rare earth group; occurs in the Scandinavian mineral thortveitite