scrap iron vs atomic number 26

scrap iron and atomic number 26 both are nouns.

Word	Noun	Adjective	Verb	Adverb
scrap iron	Yes	No	No	No
atomic number 26	Yes	No	No	No

As nouns, atomic number 26 is a hypernym of scrap iron; that is, atomic number 26 is a word with a broader meaning than scrap iron:

scrap iron: iron to be melted again and reworked
atomic number 26: a heavy ductile magnetic metallic element; is silver-white in pure form but readily rusts; used in construction and tools and armament; plays a role in the transport of oxygen by the blood

Other hypernyms of scrap iron include Fe, iron, scrap metal.

scrap iron (noun)	atomic number 26 (noun)
iron to be melted again and reworked	a heavy ductile magnetic metallic element; is silver-white in pure form but readily rusts; used in construction and tools and armament; plays a role in the transport of oxygen by the blood