atomic number 55 vs cesium

atomic number 55 and cesium both are nouns.

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

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

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

Other synonyms of atomic number 55 include caesium, Cs.

atomic number 55 (noun)	cesium (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