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

Explanation

CE(Z=58)=`[Xe]^(54)4f^(1)5d^(1)6s^(2),Ce^(3+)=[Xe]^(54)4f^(1)` ( only one unpaired electron ).
Magnetic moment `(mu)=sqrt(n(n+2))=sqrt(3)=1.73 BM`