Pb vs carbon group element

Pb and carbon group element both are nouns.

Word	Noun	Adjective	Verb	Adverb
Pb	Yes	No	No	No
carbon group element	Yes	No	No	No

As nouns, carbon group element is a hypernym of Pb; that is, carbon group element is a word with a broader meaning than Pb:

Pb: a soft heavy toxic malleable metallic element; bluish white when freshly cut but tarnishes readily to dull grey
carbon group element: any chemical element that belongs to the carbon group.

Other hypernyms of Pb include metal, metallic element, crystallogen, Group 14 element, tetragen, tetrel.

Pb (noun)	carbon group element (noun)
a unit of information equal to 1000 terabits or 10^15 bits	any chemical element that belongs to the carbon group.
a soft heavy toxic malleable metallic element; bluish white when freshly cut but tarnishes readily to dull grey