Sb vs atomic number 51

Sb and atomic number 51 both are nouns.

Word	Noun	Adjective	Verb	Adverb
Sb	Yes	No	No	No
atomic number 51	Yes	No	No	No

As nouns, Sb and atomic number 51 are synonyms defined as:

Sb and atomic number 51: a metallic element having four allotropic forms; used in a wide variety of alloys; found in stibnite

Other synonyms of Sb include antimony.

Sb (noun)	atomic number 51 (noun)
a metallic element having four allotropic forms; used in a wide variety of alloys; found in stibnite	a metallic element having four allotropic forms; used in a wide variety of alloys; found in stibnite