8.38 What can be inferred from the magnetic moment values of the following complex species ?

Example                                    Magnetic Moment (BM)

K_{4}[Mn(CN)_{6})                                2.2

[Fe(H_{2}O)_{6}]^{2+}                                          5.3

K_{2}[MnCl_{4}]                                            5.9

Answers (1)
M manish

Magnetic moment is given as - \mu = \sqrt{n(n+2)}
Putting the value on n = 1, 2, 3, 4, 5  (number of unpaired electrons in d-orbital)
we get the value of \mu are 1.732, 2.83, 3.87, 4.899, 5.92 respectively.

By comparing with our calculation we get the values n nearest to 1. It means, in above compound d-orbital has one unpaired electron(Mn^{2+} = [d^{5}]), which means CN is astrong field ligand that cause force pairing of the electron.

After comparing with our calculation the nearest value of n = 4. Here iron is in +2 oxidation state (d^{6} configuration). So, we can say that H_{2}O is a weak field ligand, which not cause any force pairing.

By observing we get the nearest value of n is 5. So, in this complex Manganese has d^{5} configuration. So, we conclude that Cl  ligand does not cause any force pairing and hence it is a weak ligand.