Rg vs chemical element

Rg and chemical element both are nouns.

Word	Noun	Adjective	Verb	Adverb
Rg	Yes	No	No	No
chemical element	Yes	No	No	No

As nouns, chemical element is a hypernym of Rg; that is, chemical element is a word with a broader meaning than Rg:

Rg: a radioactive transuranic element, with atomic number 111
chemical element: any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter

Other hypernyms of Rg include element.

Rg (noun)	chemical element (noun)
a radioactive transuranic element, with atomic number 111	any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter