pig lead vs atomic number 82

pig lead and atomic number 82 both are nouns.

Word	Noun	Adjective	Verb	Adverb
pig lead	Yes	No	No	No
atomic number 82	Yes	No	No	No

As nouns, atomic number 82 is a hypernym of pig lead; that is, atomic number 82 is a word with a broader meaning than pig lead:

pig lead: lead that is cast in pigs
atomic number 82: a soft heavy toxic malleable metallic element; bluish white when freshly cut but tarnishes readily to dull grey

Other hypernyms of pig lead include lead, Pb.

pig lead (noun)	atomic number 82 (noun)
lead that is cast in pigs	a soft heavy toxic malleable metallic element; bluish white when freshly cut but tarnishes readily to dull grey