( ( ( ( ( ( ( 14C and ) 12C ) ( are ( ( both isotopes ) ( of ( carbon ( -LRB- ( ( ( they each ) ( have ( ( ( six protons ) -- ) ( ( the ( atomic number ) ) ( is ( the same ) ) ) ) ) ) -RRB- ) ) ) ) ) ) ) , ) but ) ( they ( have ( ( a ( different number ) ) ( of ( neutrons ( -LRB- ( ( ( thus ( the ( atomic weight ) ) ) ( is different ) ) -RRB- ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (CD 14C) (CC and) (CD 12C)) (VP (VBP are) (NP (NP (DT both) (NNS isotopes)) (PP (IN of) (NP (NP (NN carbon)) (PRN (-LRB- -LRB-) (S (NP (PRP they) (DT each)) (VP (VBP have) (NP (NP (CD six) (NNS protons)) (: --) (S (NP (DT the) (JJ atomic) (NN number)) (VP (VBZ is) (NP (DT the) (JJ same))))))) (-RRB- -RRB-))))))) (, ,) (CC but) (S (NP (PRP they)) (VP (VBP have) (NP (NP (DT a) (JJ different) (NN number)) (PP (IN of) (NP (NP (NNS neutrons)) (PRN (-LRB- -LRB-) (S (NP (RB thus) (DT the) (JJ atomic) (NN weight)) (VP (VBZ is) (ADJP (JJ different)))) (-RRB- -RRB-))))))) (. .)))
14C and 12C are both isotopes of carbon (they each have six protons -- the atomic number is the same), but they have a different number of neutrons (thus the atomic weight is different).
(ROOT (S (NP (DT All) (NN carbon) (NNS atoms)) (VP (VBP have) (NP (CD six) (NNS protons))) (. .)))