( ( Each ( water molecule ) ) ( ( ( ( consists ( of ( ( 2 atoms ) ( of ( hydrogen bonded ) ) ) ) ) ( to ( ( 1 atom ) ( of oxygen ) ) ) ) and ) ( thus ( has ( the ( chemical ( formula ( H ( 2 O. ) ) ) ) ) ) ) ) )
(ROOT (S (NP (DT Each) (NN water) (NN molecule)) (VP (VP (VBZ consists) (PP (IN of) (NP (NP (CD 2) (NNS atoms)) (PP (IN of) (NP (NN hydrogen) (NNS bonded))))) (PP (TO to) (NP (NP (CD 1) (NN atom)) (PP (IN of) (NP (NN oxygen)))))) (CC and) (VP (ADVP (RB thus)) (VBZ has) (NP (DT the) (NN chemical) (NN formula) (NNP H) (CD 2) (NNP O.))))))
Each water molecule consists of 2 atoms of hydrogen bonded to 1 atom of oxygen and thus has  the chemical formula H 2 O.
(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.