The crystal field stabilization energy of $[\mathrm{Cr(NH_3)_6}]^{3+}$ with $\Delta_o$ value of $21600\ \mathrm{cm^{-1}}$ is $y\ \mathrm{cm^{-1}}$. The value of $|y|$ is ___. (rounded off to the nearest integer)
Cr(III) is a $d^3$ ion. In an octahedral field the three electrons all go into the lower $t_{2g}$ orbitals, $t_{2g}^3e_g^0$.
**Crystal field stabilisation energy:** each $t_{2g}$ electron contributes $-0.4\Delta_o$ and each $e_g$ electron $+0.6\Delta_o$: $$\text{CFSE}=3(-0.4\Delta_o)+0(0.6\Delta_o)=-1.2\Delta_o .$$