Q. The spin-only magnetic moment of $\left[crF_{6}\right]^{4-}$ (atomic number of Cr is 24) is
WBJEEWBJEE 2016
Solution:
$_{24}Cr=\left[Ar \right]3d^{5} 4s^{1}, Cr^{2+}$
F- is a weak field ligand, $\bigtriangleup_{0} < P, No \,\, pairing$
$\left[CrF_{6}\right]^{-4}=$
No. of unpaired $\overline{e}$ =4, Spin only magnetic moment $\left(\mu\right)$
$=\sqrt{n\left(n+2\right)}=\sqrt{4\times6} =\sqrt{24} =4.9 BM$
