( ( If ( ( an atom ) ( has ( six protons ) ) ) ) ( , ( it ( ( is carbon ) . ) ) ) )
(ROOT (S (SBAR (IN If) (S (NP (DT an) (NN atom)) (VP (VBZ has) (NP (CD six) (NNS protons))))) (, ,) (NP (PRP it)) (VP (VBZ is) (NP (NN carbon))) (. .)))
If an atom has six protons, it is carbon.
(ROOT (S (NP (DT All) (NN carbon) (NNS atoms)) (VP (VBP have) (NP (CD six) (NNS protons))) (. .)))