( ( Isotopes ( of ( an element ) ) ) ( ( ( ( have ( ( the ( same number ) ) ( of protons ) ) ) but ) ( differ ( in ( ( the number ) ( of neutrons ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNS Isotopes)) (PP (IN of) (NP (DT an) (NN element)))) (VP (VP (VBP have) (NP (NP (DT the) (JJ same) (NN number)) (PP (IN of) (NP (NNS protons))))) (CC but) (VP (VBP differ) (PP (IN in) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NNS neutrons))))))) (. .)))
Isotopes of an element have the same number of protons but differ in the number of neutrons.
(ROOT (S (S (NP (PRP You)) (VP (VBP call) (NP (NP (DT a) (NN substance)) (SBAR (WHNP (WDT that)) (S (VP (MD can) (RB not) (VP (VB be) (VP (VBN separated) (PP (IN into) (NP (NP (JJR smaller) (NNS pieces)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (ADVP (RB also)) (VP (VBN defined) (PP (IN by) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NNS protons))))))))))))))))))) (NP (PRP it)) (VP (VP (VBZ has)) (, ,) (NP (DT a) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (NN element))) (. .)))