atom vs carbon atom

atom and carbon atom both are nouns.

Word	Noun	Adjective	Verb	Adverb
atom	Yes	No	No	No
carbon atom	Yes	No	No	No

As nouns, carbon atom is a hyponym of atom; that is, carbon atom is a word with a more specific, narrower meaning than atom:

atom: (physics and chemistry) the smallest component of an element having the chemical properties of the element
carbon atom: an atom of carbon

Other hyponyms of atom include isotope, monad, hydrogen atom, free radical, radical.

atom (noun)	carbon atom (noun)
(physics and chemistry) the smallest component of an element having the chemical properties of the element	an atom of carbon
(nontechnical usage) a tiny piece of anything