Use Hund's rule to derive the electronic configuration of `Ce^(3+)` ion, and calculate its magnetic moment on the basis of spin-only formula.

Explanation

`Ce : 1 s^(2)2s^(2)2p^(6)3s^(2)3 p^(6)3d^(10)4s^(2)4p^(6) 4d^(10)5s^(2)5p^(6)4f^(1)5d^(1)6s^(2)`
Magnetic moment can be calculated as:
`mu=sqrt(n(n+2))`
Where,
n = number of unpaired electrons
The electronic configuration of ` 1s^(2)2s^(2)2p(6)3s(2)3p^(6)3d^(10)4s^(2)4p^(6)4d^(10)5s^(2)5p^(6)4f^(1)`
In `Ce^(3+), n = 1`
`therefore mu = 1 ( 1 +2 ) = 3 = 1.732` B.M