( ( ( ( ( ( All ( carbon atoms ) ) ( have ( six protons ) ) ) , ) but ) ( ( isotopes ( of carbon ) ) ( can ( have ( ( ( ( ( 12 , ) 13 ) , ) or ) ( 14 neutrons ) ) ) ) ) ) . )
(ROOT (S (S (NP (DT All) (NN carbon) (NNS atoms)) (VP (VBP have) (NP (CD six) (NNS protons)))) (, ,) (CC but) (S (NP (NP (NNS isotopes)) (PP (IN of) (NP (NN carbon)))) (VP (MD can) (VP (VB have) (NP (NP (CD 12)) (, ,) (NP (CD 13)) (, ,) (CC or) (NP (CD 14) (NNS neutrons)))))) (. .)))
All carbon atoms have six protons, but isotopes of carbon can have 12, 13, or 14 neutrons.
(ROOT (S (NP (DT All) (NN carbon) (NNS atoms)) (VP (VBP have) (NP (CD six) (NNS protons))) (. .)))