Geometric Isomers
The C=C bond has restricted rotation. Groups attached to each carbon cannot move around. If there are two different groups on each carbon atom of the C=C bond then there are two different spatial arrangements.
If one of the groups on each carbon atom is the same (for example, each carbon has an H atom) then cis-trans notation can be used. If all the groups are different, then E-Z notation is used. With E-Z notation molecules with the highest priority groups (highest atomic number) on the same side are Z-isomers and on the opposite side are E-isomers.
