Gd vs metallic element

Gd and metallic element both are nouns.

Word	Noun	Adjective	Verb	Adverb
Gd	Yes	No	No	No
metallic element	Yes	No	No	No

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

Gd: a ductile silvery-white ductile ferromagnetic trivalent metallic element of the rare earth group
metallic element: any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.

Other hypernyms of Gd include metal.

Gd (noun)	metallic element (noun)
a ductile silvery-white ductile ferromagnetic trivalent metallic element of the rare earth group	any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.