When a molecule has one carbon-carbon double bond and four monovalent atoms or groups in which two atoms on same carbon are different, there will be 2 isomers, one cis and one trans.
Case 2:
When a molecule has one carbon-carbon double bond and four monovalent atoms or groups where both atoms attached to the same carbon are same, there will be no geometrical isomerism.
As based on priority, there will be only two orientations possible , in which same priority atoms are on the same side that is cis and if they are on the opposite side that is trans.
