( ( ( ( Mass number ) , ) ( ( A ( The ( total number ) ) ) ( of ( ( nucleons ( -LRB- ( ( ( protons and ) neutrons ) -RRB- ) ) ) ( in ( ( the nucleus ) ( of ( ( an atom ) ( of ( an element ) ) ) ) ) ) ) ) ) ) . )
(ROOT (NP (NP (NNP Mass) (NN number)) (, ,) (NP (NP (DT A) (DT The) (JJ total) (NN number)) (PP (IN of) (NP (NP (NP (NNS nucleons)) (PRN (-LRB- -LRB-) (NP (NP (NNS protons)) (CC and) (NP (NNS neutrons))) (-RRB- -RRB-))) (PP (IN in) (NP (NP (DT the) (NN nucleus)) (PP (IN of) (NP (NP (DT an) (NN atom)) (PP (IN of) (NP (DT an) (NN element)))))))))) (. .)))
Mass number, A The total number of nucleons (protons and neutrons) in the nucleus of an atom of an element.
(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))))) (. .)))