Question

A $3d$ series metal cation forms octahedral complexes with both ${}^{-}SCN$ as well ${}^{-}CN$ ions as ligands. The complex $\left[M\right(CN{)}_6{]}^{3-}$ has a spin only magnetic moment of $\sqrt{3}BM$ whereas the complex ${\left[M\right(SCN{)}_6]}^{3-}$ has a spin only magnetic moment of $\sqrt{35}BM$. Then out of the following, metal $M$ can be

• A. $Fe$
• B. $Mn$
• C. $Co$
• D. $Ni$

Answer 1

The correct option is A $Fe$

$M^{3+}$ with $SC{N}^{-}$ has 5 unpaired $e^{-}$
$M^{3+}$ with $C{N}^{-}$ has 1 unpaired $e^{-}$
So, $M^{3+}$ has $d^5$ configuration

So, $M$ has $s^2{d}^6$ configuration