atomic weapon vs nuclear weapon

atomic weapon and nuclear weapon both are nouns.

Word	Noun	Adjective	Verb	Adverb
atomic weapon	Yes	No	No	No
nuclear weapon	Yes	No	No	No

As nouns, atomic weapon and nuclear weapon are synonyms defined as:

atomic weapon and nuclear weapon: a weapon of mass destruction whose explosive power derives from a nuclear reaction

atomic weapon (noun)	nuclear weapon (noun)
a weapon of mass destruction whose explosive power derives from a nuclear reaction	a weapon of mass destruction whose explosive power derives from a nuclear reaction