Question

For the octahedral complexes of $F{e}^{3+}$ in $SC{N}^{-}$(thiocyanato-S) and in $C{N}^{-}$ ligand environments, the difference between the spin-only magnetic moment in BM (when approximated to the nearest integer) is
[Atomic number of $Fe=26$]

Answer 1

$SC{N}^{-}$ is weak field effect (WFE) ligand whereas $C{N}^{-}$ is strong field effect (SFE) ligand.
Spin only magnetic moment $=\sqrt{5(5+2)}=\sqrt{35}\text{BM}$
Spin only magnetic moment $=\sqrt{1(1+2)}=\sqrt{3}\text{BM}$
Difference $=\sqrt{35}-\sqrt{3}\simeq 4$