cesium vs atomic number 55

cesium and atomic number 55 both are nouns.

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

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

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

Other synonyms of cesium include caesium, Cs.

cesium (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