( ( If ( they ( share ( four electrons ) ) ) ) ( it ( ( is ( called ( a ( double bond ) ) ) ) . ) ) )
(ROOT (S (SBAR (IN If) (S (NP (PRP they)) (VP (VBP share) (NP (CD four) (NNS electrons))))) (NP (PRP it)) (VP (VBZ is) (VP (VBN called) (NP (DT a) (JJ double) (NN bond)))) (. .)))
If they share four electrons it is called a double bond .
(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)))) (. .)))