( ( For ( a ( given element ) ) ) ( , ( ( ( ( ( two or ) more ) nuclides ) ( which ( have ( ( the ( same number ) ) ( of ( ( ( ( protons but ) different ) numbers ) ( of ( neutrons ( in ( their nuclei ) ) ) ) ) ) ) ) ) ) ( ( are ( called isotopes ) ) . ) ) ) )
(ROOT (S (PP (IN For) (NP (DT a) (VBN given) (NN element))) (, ,) (NP (NP (QP (CD two) (CC or) (JJR more)) (NNS nuclides)) (SBAR (WHNP (WDT which)) (S (VP (VBP have) (NP (NP (DT the) (JJ same) (NN number)) (PP (IN of) (NP (NP (ADJP (JJ protons) (CC but) (JJ different)) (NNS numbers)) (PP (IN of) (NP (NP (NNS neutrons)) (PP (IN in) (NP (PRP$ their) (NNS nuclei)))))))))))) (VP (VBP are) (VP (VBN called) (NP (NNS isotopes)))) (. .)))
For a given element, two or more nuclides which have the same number of protons but different numbers of neutrons in their nuclei are called isotopes.
(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))) (. .)))