( ( ( The ( atomic mass ) ) ( -LRB- ( ( also ( ( referred to ) ( as ( the ( atomic weight ) ) ) ) ) -RRB- ) ) ) ( ( is ( ( the number ) ( of ( ( ( protons and ) neutrons ) ( in ( an atom ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ atomic) (NN mass)) (PRN (-LRB- -LRB-) (VP (ADVP (RB also)) (VBN referred) (S (VP (TO to))) (PP (IN as) (NP (DT the) (JJ atomic) (NN weight)))) (-RRB- -RRB-))) (VP (VBZ is) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NP (NNS protons) (CC and) (NNS neutrons)) (PP (IN in) (NP (DT an) (NN atom))))))) (. .)))
The atomic mass (also referred to as the atomic weight) is the number of protons and neutrons in an atom.
(ROOT (S (NP (NP (DT The) (NN sum)) (PP (IN of) (NP (NP (DT the) (NNS masses)) (PP (IN of) (NP (NP (DT the) (NNS atoms)) (PP (IN in) (NP (DT the) (NN formula)))))))) (VP (VBZ is) (VP (VBN referred) (PP (TO to) (NP (RB as) (JJ molecular) (NN mass))))) (. .)))