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

The correct order of the following complexes in terms of their crystal field stabilization energies $(CFSE)$ is:

The Crystal Field Stabilization Energy $(CFSE)$ and magnetic moment (spin-only) of an octahedral aqua complex of a metal ion $(M^{2+})$ are $-0.8\, \Delta_{0}$ and $3.87\, BM$,respectively. Identify $(M^{2+})$:

Number of complexes with an even number of electrons in $t_{2g}$ orbitals is -
$[Fe(H_2O)_6]^{2+}, [Co(H_2O)_6]^{2+}, [Co(H_2O)_6]^{3+}, [Cu(H_2O)_6]^{2+}, [Cr(H_2O)_6]^{2+}$

The magnitude of crystal field stabilisation energy in octahedral field depends on :
$I.$ The nature of the ligand
$II.$ The charge on the metal ion
$III.$ Whether the metal is in the first,second or third row of the transition elements

For which of the following pairs of complexes is the crystal field splitting energy $\Delta_0$ for $II > \Delta_0$ for $I$?

$I$	$II$
$(a). [Cr(H_2O)_6]^{2+}$	$[Cr(H_2O)_6]^{3+}$
$(b). [Fe(H_2O)_6]^{3+}$	$[Fe(CN)_6]^{3-}$
$(c). [Fe(CN)_6]^{3-}$	$[Ru(CN)_6]^{3-}$
$(d). [NiF_6]^{4-}$	$[NiF_6]^{2-}$