( ( ( ( Mass number ) -- ) ( ( the number ) ( of ( ( ( neutrons and ) protons ) ( in ( ( the nucleus ) ( of ( an atom ) ) ) ) ) ) ) ) . )
(ROOT (NP (NP (NNP Mass) (NN number)) (: --) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NP (NNS neutrons) (CC and) (NNS protons)) (PP (IN in) (NP (NP (DT the) (NN nucleus)) (PP (IN of) (NP (DT an) (NN atom)))))))) (. .)))
Mass number--the number of neutrons and protons in the nucleus of an atom.
(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))))) (. .)))