rubidium vs Rb

rubidium and Rb both are nouns.

Word	Noun	Adjective	Verb	Adverb
rubidium	Yes	No	No	No
Rb	Yes	No	No	No

As nouns, rubidium and Rb are synonyms defined as:

rubidium and Rb: a soft silvery metallic element of the alkali metal group; burns in air and reacts violently in water; occurs in carnallite and lepidolite and pollucite

Other synonyms of rubidium include atomic number 37.

rubidium (noun)	Rb (noun)
a soft silvery metallic element of the alkali metal group; burns in air and reacts violently in water; occurs in carnallite and lepidolite and pollucite	a soft silvery metallic element of the alkali metal group; burns in air and reacts violently in water; occurs in carnallite and lepidolite and pollucite