H cis-1. 2-Difluoroethene trans-1.2-Difluoroethene F F Cl C cis-1. 2-Dichloro-12-difluoroethene tranS-1. 2-Dichloro-1 2-difluoroethene Note; cis-trans isomerism of this type is not possible if one carbon atom of the double bond bears two identical groups bF H F H F Cl F Cl F H H F cis-1,2-Difluoroethene trans-1,2-Difluoroethene F Cl Cl F cis-1,2-Dichloro-1,2-difluoroethene trans-1,2-Dichloro-1,2-difluoroethene Note; cis-trans isomerism of this type is not possible if one carbon atom of the double bond bears two identical groups. a a a b a b d d