( ( ( The ( total number ) ) ( of ( ( ( protons and ) neutrons ) ( in ( the nucleus ) ) ) ) ) ( is ( ( ( the ( mass number ) ) , ) A. ) ) )
(ROOT (S (NP (NP (DT The) (JJ total) (NN number)) (PP (IN of) (NP (NP (NNS protons) (CC and) (NNS neutrons)) (PP (IN in) (NP (DT the) (NN nucleus)))))) (VP (VBZ is) (NP (NP (DT the) (JJ mass) (NN number)) (, ,) (NP (NNP A.))))))
The total number of protons and neutrons in the nucleus is the mass number, A.
(ROOT (S (NP (NP (DT The) (NN mass)) (PP (IN of) (NP (NNS atoms)))) (VP (VBZ is) (VP (VBN based) (PP (IN on) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NNS protons) (CC and) (NNS neutrons))))) (PP (IN in) (NP (NN nucleus))))) (. .)))