( ( Unlike protons ) ( , ( ( the neutrons ) ( ( may ( ( vary ( in number ) ) ( among ( atoms ( of ( the ( same element ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN Unlike) (NP (NNS protons))) (, ,) (NP (DT the) (NNS neutrons)) (VP (MD may) (VP (VB vary) (PP (IN in) (NP (NN number))) (PP (IN among) (NP (NP (NNS atoms)) (PP (IN of) (NP (DT the) (JJ same) (NN element))))))) (. .)))
Unlike protons, the neutrons may vary in number among atoms of the same element.
(ROOT (S (NP (NP (DT The) (NN number)) (PP (IN of) (NP (NNS neutrons)))) (VP (MD can) (VP (VB vary) (PP (IN between) (NP (NP (NNS atoms)) (PP (IN of) (NP (DT the) (JJ same) (NN element))))))) (. .)))