( ( ( Formula weight ) ( of ( ( a substance ) ( -LRB- ( ( ionic compound ) -RRB- ) ) ) ) ) ( ( is ( ( the sum ) ( of ( ( the ( atomic weight ) ) ( of ( ( all elements ) ( participated ( in ( making ( ( a ( formula unit ) ) ( of ( the substance ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Formula) (NN weight)) (PP (IN of) (NP (NP (DT a) (NN substance)) (PRN (-LRB- -LRB-) (NP (JJ ionic) (NN compound)) (-RRB- -RRB-))))) (VP (VBZ is) (NP (NP (DT the) (NN sum)) (PP (IN of) (NP (NP (DT the) (JJ atomic) (NN weight)) (PP (IN of) (NP (NP (DT all) (NNS elements)) (VP (VBN participated) (PP (IN in) (S (VP (VBG making) (NP (NP (DT a) (NN formula) (NN unit)) (PP (IN of) (NP (DT the) (NN substance)))))))))))))) (. .)))
Formula weight of a substance (ionic compound) is the sum of the atomic weight of all elements participated in making a formula unit of the substance.
(ROOT (S (NP (NNS Elements)) (VP (VBP are) (NP (NP (JJ pure) (NNS substances)) (SBAR (WHNP (WDT that)) (S (VP (VBP make) (ADVP (RB up) (DT all) (NN matter))))))) (. .)))