Xe vs noble gas

Xe and noble gas both are nouns.

Word	Noun	Adjective	Verb	Adverb
Xe	Yes	No	No	No
noble gas	Yes	No	No	No

As nouns, noble gas is a hypernym of Xe; that is, noble gas is a word with a broader meaning than Xe:

Xe: a colorless odorless inert gaseous element occurring in the earth's atmosphere in trace amounts
noble gas: any of the chemically inert gaseous elements of the helium group in the periodic table

Other hypernyms of Xe include argonon, inert gas.

Xe (noun)	noble gas (noun)
a colorless odorless inert gaseous element occurring in the earth's atmosphere in trace amounts	any of the chemically inert gaseous elements of the helium group in the periodic table