( ( ( Percent Composition ) ( of ( Compounds 16 ) ) ) . )
(ROOT (NP (NP (NNP Percent) (NNP Composition)) (PP (IN of) (NP (NNP Compounds) (CD 16))) (. .)))
Percent Composition of Compounds 16.
(ROOT (S (NP (DT The) (NN term) (NN percent) (NN composition)) (VP (VBZ means) (NP (DT the) (NN percentage)) (PP (IN by) (NP (NP (NN mass)) (PP (IN of) (NP (NP (DT each) (NN element)) (PP (IN in) (NP (DT a) (NN compound)))))))) (. .)))