( ( ( The valence ) ( of ( an atom ) ) ) ( ( is ( ( the number ) ( of ( bonds ( it ( will ( form ( to ( give ( a ( neutral species ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN valence)) (PP (IN of) (NP (DT an) (NN atom)))) (VP (VBZ is) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NP (NNS bonds)) (SBAR (S (NP (PRP it)) (VP (MD will) (VP (VB form) (S (VP (TO to) (VP (VB give) (NP (DT a) (JJ neutral) (NN species))))))))))))) (. .)))
The valence of an atom is the number of bonds it will form to give a neutral species.
(ROOT (S (NP (NNP Valence)) (VP (VBZ is) (NP (NP (DT the) (NN term)) (PP (IN for) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (JJ covalent) (NNS bonds))))) (SBAR (S (NP (DT an) (NN atom)) (VP (MD can) (VP (VB form))))))) (. .)))
Valence is the term for the number of covalent bonds an atom can form.