( ( ( ( mass number ) - ) ( ( Total number ) ( of ( ( ( protons and ) neutrons ) ( in ( ( the nucleus ) ( of ( an ( ( atom or ) ion ) ) ) ) ) ) ) ) ) . )
(ROOT (NP (NP (JJ mass) (NN number)) (: -) (NP (NP (JJ Total) (NN number)) (PP (IN of) (NP (NP (NNS protons) (CC and) (NNS neutrons)) (PP (IN in) (NP (NP (DT the) (NN nucleus)) (PP (IN of) (NP (DT an) (NN atom) (CC or) (NN ion)))))))) (. .)))
mass number - Total number of protons and neutrons in the nucleus of an atom or ion.
(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))))) (. .)))