( ( ( ( ( ( The ( atomic number ) ) ( -LRB- ( Z -RRB- ) ) ) ( is ( equal ( to ( ( the number ) ( of ( protons ( in ( the nucleus ) ) ) ) ) ) ) ) ) and ) ( ( ( the ( mass number ) ) ( -LRB- ( A -RRB- ) ) ) ( ( is ( equal ( to ( ( the sum ) ( of ( ( ( ( protons ( -LRB- ( Z -RRB- ) ) ) and ) neutrons ) ( -LRB- ( N -RRB- ) ) ) ) ) ) ) ) ( in ( the nucleus ) ) ) ) ) . )
(ROOT (S (S (NP (NP (DT The) (JJ atomic) (NN number)) (PRN (-LRB- -LRB-) (NP (NNP Z)) (-RRB- -RRB-))) (VP (VBZ is) (ADJP (JJ equal) (PP (TO to) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NP (NNS protons)) (PP (IN in) (NP (DT the) (NN nucleus)))))))))) (CC and) (S (NP (NP (DT the) (JJ mass) (NN number)) (PRN (-LRB- -LRB-) (NP (NNP A)) (-RRB- -RRB-))) (VP (VBZ is) (ADJP (JJ equal) (PP (TO to) (NP (NP (DT the) (NN sum)) (PP (IN of) (NP (NP (NNS protons)) (PRN (-LRB- -LRB-) (NP (NNP Z)) (-RRB- -RRB-)) (CC and) (NP (NNS neutrons)) (PRN (-LRB- -LRB-) (NP (NNP N)) (-RRB- -RRB-))))))) (PP (IN in) (NP (DT the) (NN nucleus))))) (. .)))
The atomic number (Z) is equal to the number of protons in the nucleus and the mass number (A) is equal to the sum of protons (Z) and neutrons (N) in 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))))) (. .)))