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)^(3+)=[(Xe)] 4 (f)^(l) (Ce)^(l)+). is paramagnetic
.mu_( magnetic )^(*)=sqrt(n(n+2).
n= number of unpaired electrons .(Ce)^(2). has only one unpaired electron of 4f subshell
i.e. n=1
.+mu_( magnetic )=sqrt(1(1+2)=sqrt(3)=1.73 (~B): (M).