( ( Each ( water molecule ) ) ( ( contains ( ( ( ( ( 3 atoms ) , ) ( 2 ( of hydrogen ) ) ) and ) ( 1 ( of oxygen ) ) ) ) . ) )
(ROOT (S (NP (DT Each) (NN water) (NN molecule)) (VP (VBZ contains) (NP (NP (CD 3) (NNS atoms)) (, ,) (NP (NP (CD 2)) (PP (IN of) (NP (NN hydrogen)))) (CC and) (NP (NP (CD 1)) (PP (IN of) (NP (NN oxygen)))))) (. .)))
Each water molecule contains 3 atoms, 2 of hydrogen and 1 of oxygen.
(ROOT (S (NP (NP (CD 2) (NN hydrogen)) (, ,) (NP (CD 1) (NN oxygen) (NNS atoms))) (VP (VBP combine) (S (VP (TO to) (VP (VB make) (PRT (RP up)) (NP (NP (DT a) (NN molecule)) (PP (IN of) (NP (NN water)))))))) (. .)))
2 hydrogen, 1 oxygen atoms combine to make up a molecule of water.