Identify the correct decreasing order of wavelength of light absorbed for the following complex ions:
$I. [Co(H_2O)_6]^{3+}$
$II. [Co(CN)_6]^{3-}$
$III. [CoI_6]^{3-}$
$IV. [Co(en)_3]^{3+}$

The value of $CFSE$ in a tetrahedral complex having a $3d^4$ configuration of the metal ion,surrounded by strong field ligands,will be:

The Crystal Field Stabilisation Energy $(CFSE)$ for $[CoCl_{6}]^{4-}$ is $18000 \; cm^{-1}$. The $CFSE$ for $[CoCl_{4}]^{2-}$ will be $...... \ cm^{-1}$.

Simplified absorption spectra of three complexes $(i), (ii)$ and $(iii)$ of $M^{n+}$ ion are provided below; their $\lambda_{max}$ values are marked as $A, B$ and $C$ respectively. The correct match between the complexes and their $\lambda_{max}$ values is
$(i)$ $[M(NCS)_6]^{(-6+n)}$
$(ii)$ $[MF_6]^{(-6+n)}$
$(iii)$ $[M(NH_3)_6]^{n+}$

The order of energy absorbed,which is responsible for the color of the following complexes,is:

The crystal field stabilisation energy $(CFSE)$ and the spin-only magnetic moment in Bohr Magneton $(BM)$ for the complex $K_3[Fe(CN)_6]$ are,respectively