Geometric isomerism Occurs when atoms rigid structure

In geometric isomers, or cis-trans isomers, of coordination compounds, the same ligands are arranged in different orders within the coordination sphere. Geometric isomerism occurs when atoms or groups of atoms can be arranged on two sides of a rigid structure. Cis means adjacent to and trans means on the opposite side of. Cis- and trans-diamminedichloroplatinum(II) are shown below. 

---