The calculate value of magnetic moment of ${ }_{23}{\mathrm{V}}^{3+}$ is 

The electronic configuration of ${ }_{23}{\mathrm{V}}^{3+}$ is $3{\mathrm{d}}^2$. It contains two unpaired electrons. Hence,$\mu /{\mu }_{\mathrm{B}}=\sqrt{2(2+2)}=2.83$.