( ( ( ( The number ) ( of ( ( protons plus ) neutrons ) ) ) ( in ( ( the nucleus ) ( of ( an atom ) ) ) ) ) . )
(ROOT (NP (NP (DT The) (NN number)) (PP (IN of) (NP (NNS protons) (CC plus) (NNS neutrons))) (PP (IN in) (NP (NP (DT the) (NN nucleus)) (PP (IN of) (NP (DT an) (NN atom))))) (. .)))
The number of protons plus neutrons in the nucleus of an atom.
(ROOT (S (S (S (VP (VBG Adding) (NP (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NNS protons)))) (CC plus) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NP (NNS neutrons)) (PP (IN in) (NP (DT an) (NN atom))))))))) (VP (VBZ decides) (NP (PRP$ its) (JJ approximate) (NN mass)))) (: ;) (S (NP (JJ atomic) (NN number)) (VP (VBZ is) (NP (NP (DT another) (NN word)) (PP (IN for) (NP (DT this) (NN value)))))) (. .)))