caesium vs atomic number 55

caesium and atomic number 55 both are nouns.

Word	Noun	Adjective	Verb	Adverb
caesium	Yes	No	No	No
atomic number 55	Yes	No	No	No

As nouns, caesium and atomic number 55 are synonyms defined as:

caesium and atomic number 55: a soft silver-white ductile metallic element (liquid at normal temperatures); the most electropositive and alkaline metal

Other synonyms of caesium include cesium, Cs.

caesium (noun)	atomic number 55 (noun)
a soft silver-white ductile metallic element (liquid at normal temperatures); the most electropositive and alkaline metal	a soft silver-white ductile metallic element (liquid at normal temperatures); the most electropositive and alkaline metal