( ( If ( ( an atom ) ( has ( ( 6 protons ) ( in ( its nucleus ) ) ) ) ) ) ( , ( it ( ( is ( a ( carbon atom ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN If) (S (NP (DT an) (NN atom)) (VP (VBZ has) (NP (NP (CD 6) (NNS protons)) (PP (IN in) (NP (PRP$ its) (NN nucleus))))))) (, ,) (NP (PRP it)) (VP (VBZ is) (NP (DT a) (NN carbon) (NN atom))) (. .)))
If an atom has 6 protons in its nucleus, it is a carbon atom.
(ROOT (S (NP (NP (DT A) (NN carbon) (NN atom)) (PP (IN with) (NP (NP (CD 6) (NNS protons)) (CC and) (NP (CD 8) (NNS neutrons))))) (VP (VBZ is) (ADVP (RBR more) (RB specifically)) (VP (VBN known) (PP (IN as) (NP (NN carbon) (CD 14))))) (. .)))
A carbon atom with 6 protons and 8 neutrons is more specifically known as carbon 14.