Hg vs atomic number 80

Hg and atomic number 80 both are nouns.

Word	Noun	Adjective	Verb	Adverb
Hg	Yes	No	No	No
atomic number 80	Yes	No	No	No

As nouns, Hg and atomic number 80 are synonyms defined as:

Hg and atomic number 80: a heavy silvery toxic univalent and bivalent metallic element; the only metal that is liquid at ordinary temperatures

Other synonyms of Hg include hydrargyrum, mercury, quicksilver.

Hg (noun)	atomic number 80 (noun)
a heavy silvery toxic univalent and bivalent metallic element; the only metal that is liquid at ordinary temperatures	a heavy silvery toxic univalent and bivalent metallic element; the only metal that is liquid at ordinary temperatures