Use Hund’s rule to derive the electronic configuration of Ce3+ ion, and calculate its magnetic moment on the basis of
‘spin-only’ formula.

Step 1:

The electronic configuration of Ce and Ce3+ are as follows:

Ce : [Xe] 4f1 5d1 6s2 
Ce3+: [Xe] 4f1 

It has one unpaired electron. 

Step 2:

Calculate the magnetic moment as follows:

Magnetic moment = \(\sqrt{n(n+2)}BM\)
Here, n is number of unpaired electron.

The value of magnetic moment is as follows:

Magnetic moment = \(\sqrt{1(1+2)}BM\)
= 1.73 BM