( ( ( Electrons and ) ( Chemical Periodicity ) ) ( ( covers ( ( the behavior ) ( of ( electrons ( in atoms ) ) ) ) ) ; ) )
(ROOT (S (NP (NP (NNS Electrons)) (CC and) (NP (NNP Chemical) (NNP Periodicity))) (VP (VBZ covers) (NP (NP (DT the) (NN behavior)) (PP (IN of) (NP (NP (NNS electrons)) (PP (IN in) (NP (NNS atoms))))))) (: ;)))
Electrons and Chemical Periodicity  covers the behavior of electrons in atoms;
(ROOT (S (NP (NP (DT The) (JJ chemical) (NN behavior)) (PP (IN of) (NP (NNS elements)))) (VP (MD can) (ADVP (RB largely)) (VP (VB be) (VP (VBN explained) (PP (IN by) (NP (NN electron) (NNS configurations)))))) (. .)))