( ( ( Combined weight ) ( of ( the ( ( protons and ) neutrons ) ) ) ) ( ( gives ( atomic weight ) ) . ) )
(ROOT (S (NP (NP (VBN Combined) (NN weight)) (PP (IN of) (NP (DT the) (NNS protons) (CC and) (NNS neutrons)))) (VP (VBZ gives) (NP (JJ atomic) (NN weight))) (. .)))
Combined weight of the protons and neutrons gives atomic weight.
(ROOT (S (S (VP (TO To) (VP (VB determine) (NP (NP (DT the) (JJ atomic) (NN weight)) (PP (IN of) (NP (DT an) (NN element))))))) (, ,) (NP (PRP you)) (VP (MD should) (VP (VB add) (PRT (RP up)) (NP (NNS protons) (CC and) (NNS neutrons)))) (. .)))