( ( ( The ( total number ) ) ( of ( ( protons and ) neutrons ) ) ) ( ( together ( in ( a nucleus ) ) ) ( ( is ( ( the ( atomic ( mass number ) ) ) ( of ( the nucleus ) ) ) ) . ) ) )
(ROOT (S (NP (NP (DT The) (JJ total) (NN number)) (PP (IN of) (NP (NNS protons) (CC and) (NNS neutrons)))) (ADVP (RB together) (PP (IN in) (NP (DT a) (NN nucleus)))) (VP (VBZ is) (NP (NP (DT the) (JJ atomic) (NN mass) (NN number)) (PP (IN of) (NP (DT the) (NN nucleus))))) (. .)))
The total number of protons and neutrons together in a nucleus is the atomic mass number of the nucleus.
(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))))) (. .)))