atomic number 55 vs caesium

atomic number 55 and caesium both are nouns.

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

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

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

Other synonyms of atomic number 55 include cesium, Cs.

atomic number 55 (noun)	caesium (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