The hexaquo manganese (II) ion contains five unpaired electrons, while the hexacyano ion contains only one unpaired electron. Explain using Crystal Field Theory.



[Mn(H2O)6]+2



[Mn(CN)6]4-



Oxidation state of manganese:


Overall charge balance:


X + 6(0) = 2


X = + 2



Oxidation state of manganese:


Overall charge balance:


X + 6(-1) = -4


X = + 2



Outer electronic configuration of Mn = d5



Outer electronic configuration of Mn = d5



H2O is a weak field ligand so it does not cause pairing of the electron. Therefore Mn undergoes sp3d2 hybridization. Geometry is octahedral. Therefore the 5 unpaired electrons from the d orbital remain as it is.



CN is a strong field ligand so it causes pairing of the electron(5 electrons get paired to form 2 pairs and one unpaired electron). Therefore Mn undergoes d2sp3 hybridization. Geometry is octahedral.



Mn in + 2 oxidation state:


In presence of CN- Ligands:



d2sp3 hybridisation:



Electronic configuration of [Mn(CN)6]4-:



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