Answer
As shown in the models, all four $\mathrm{Cl}^{-}$ ligands are in the same plane due to the substitution of the fourth $\mathrm{Cl}^{-}$ in the mer-isomer , but substituting a fourth $\mathrm{Cl}^{-}$ in the fic -isomer does not yield the same isomer.
Work Step by Step
See answer above.
