( ( When ( ( atoms ( of ( different elements ) ) ) ( form bonds ) ) ) ( , ( they ( ( ( do n't ) ( ( share ( the electrons ) ) equally ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NP (NNS atoms)) (PP (IN of) (NP (JJ different) (NNS elements)))) (VP (VBP form) (NP (NNS bonds))))) (, ,) (NP (PRP they)) (VP (VBP do) (RB n't) (VP (VB share) (NP (DT the) (NNS electrons)) (ADVP (RB equally)))) (. .)))
When atoms of different elements form bonds, they don't share the electrons equally.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NNS electrons)) (VP (VBP are) (VP (VBN shared) (ADVP (RB equally)))))) (, ,) (NP (PRP it)) (VP (VBZ is) (VP (VBN called) (NP (NN nonpolar) (NNS bonds)))) (. .)))