radium vs metallic element

radium and metallic element both are nouns.

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

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

radium: an intensely radioactive metallic element that occurs in minute amounts in uranium ores
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 radium include metal.

radium (noun)	metallic element (noun)
an intensely radioactive metallic element that occurs in minute amounts in uranium ores	any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.