Why do compounds having similar geometry have different magnetic moment ?

Explanation

It is due to the presence of weak and strong field ligands in complexes. If CFSE is high, the complex will show low value of magnetic moment and vice-versa, e.g. `[CoF_(6)]^(3-)` and `[Co(NH_(3))_(6)]^(3+)`, the former is paramagnetic and the latter is diamagnetic because `F^(-)` is a weak field ligand and `NH_(3)` is a strong field ligand while both have similar geometry.