( ( Electrons ( in ( ( the ( last ( energy shell ) ) ) ( of ( an atom ) ) ) ) ) ( ( ( ( are ( called ( valence electrons ) ) ) and ) ( can ( interact ( with ( other ( atoms ( and ( form bonds ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNS Electrons)) (PP (IN in) (NP (NP (DT the) (JJ last) (NN energy) (NN shell)) (PP (IN of) (NP (DT an) (NN atom)))))) (VP (VP (VBP are) (VP (VBN called) (NP (JJ valence) (NNS electrons)))) (CC and) (VP (MD can) (VP (VB interact) (PP (IN with) (NP (JJ other) (NNS atoms) (CC and) (NN form) (NNS bonds)))))) (. .)))
Electrons in the last energy shell of an atom are called valence electrons and can interact with other atoms and form bonds.
(ROOT (S (NP (NP (NNS Electrons)) (PP (IN in) (NP (NP (DT the) (JJ outer) (NN energy) (NN level)) (PP (IN of) (NP (DT an) (NN atom)))))) (VP (VBP are) (VP (VBN called) (NP (JJ valence) (NNS electrons)))) (. .)))