( ( ( The ( total number ) ) ( of ( bonds ( formed ( by ( an atom ) ) ) ) ) ) ( ( is ( called ( ( the valence ) ( of ( the atom ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ total) (NN number)) (PP (IN of) (NP (NP (NNS bonds)) (VP (VBN formed) (PP (IN by) (NP (DT an) (NN atom))))))) (VP (VBZ is) (VP (VBN called) (NP (NP (DT the) (NN valence)) (PP (IN of) (NP (DT the) (NN atom)))))) (. .)))
The total number of bonds formed by an atom is called the valence of the atom.
(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.