atomic number 3 vs Li

atomic number 3 and Li both are nouns.

Word	Noun	Adjective	Verb	Adverb
atomic number 3	Yes	No	No	No
Li	Yes	No	No	No

As nouns, atomic number 3 and Li are synonyms defined as:

atomic number 3 and Li: a soft silver-white univalent element of the alkali metal group; the lightest metal known; occurs in several minerals

Other synonyms of atomic number 3 include lithium.

atomic number 3 (noun)	Li (noun)
a soft silver-white univalent element of the alkali metal group; the lightest metal known; occurs in several minerals	a soft silver-white univalent element of the alkali metal group; the lightest metal known; occurs in several minerals