9.29 Amongst the following ions which one has the highest magnetic moment value?

(i) [Cr(H2O)6]3+        (ii) [Fe(H2O)6]2+            

(iii) [Zn(H2O)6]2+ 

Step 1:

The formula for calculating magnetic moment is as follows:

 µ = \(\sqrt{n(n+2)}BM\)

Here, n is the number of unpaired electrons

Step 2:

(i)

In [Cr(H2O)6]3+, Cr oxidation state is +3 and it is a 3d3 system.

No. of unpaired electrons in [Cr(H2O)6]3+ = 3
 
Then, μ = n(n+2)                = 3(3+2)               = 15                 ~4 BM
 
(ii)
In [Fe(H2O)6]2+, Fe oxidation state is +2 and it is a 3d6 system.
No. of unpaired electrons in [Fe(H2O)6]2+ = 4
Then, μ = 4(4+2)                = 24                 ~5 BM
(iii)
In [Zn(H2O)6]2+, Zn oxidation state is +2 and it is a 3d10 system

No. of unpaired electrons in [Zn(H2O)6]2+ = 0
Hence, [Fe(H2O)6]2+ has the highest magnetic moment value.