Chemistry - f-block Question with Solution | TestHub

In case of lanthanoids, 4 f orbitals lie too deep and hence the magnetic effect of the motion of the electron in its orbital is not quenched out. Here spin contribution $\mathrm{S}$ and orbital contribution $\mathrm{L}$ couple together to give a new quantum number $\mathrm{J}$. Thus magnetic moment of lanthanoids is given by, $\mu =g\sqrt{J(J+1)}$ where $\mathrm{J}=\mathrm{L}-\mathrm{S}$ when the shell is less than half fill $\mathrm{J}=\mathrm{L}+\mathrm{S}$ when the shell is more than half fill and $\mathrm{g}=1\frac{1}{2}+\frac{\mathrm{S}(\mathrm{S}+1)-\mathrm{L}(\mathrm{L}+1)}{2\mathrm{J}(\mathrm{J}+1)}$