The correct statement about the magnetic properties of \(\left[\mathrm{Fe}(\mathrm{CN})_6\right]^{3-}\) and \(\left[\mathrm{FeF}_6\right]^{3-}\) is

• Correct answer
  A

  Both are paramagnetic
• B

  Both are diamagnetic
• C

  \(\left[\mathrm{Fe}(\mathrm{CN})_6\right]^{3-}\) is diamagnetic, \(\left[\mathrm{FeF}_6\right]^{3-}\) is paramagnetic
• D

  \(\left[\mathrm{Fe}(\mathrm{CN})_6\right]^{3-}\) is paramagnetic, \(\left[\mathrm{FeF}_6\right]^{3-}\) is diamagnetic

Solution

Hint : \(\mathrm{Fe}^{+3}=[\mathrm{Ar}] 3 \mathrm{~d}^5 4 \mathrm{~s}^0\) For \(\left[\mathrm{Fe}(\mathrm{CN})_6\right]^{3-}\)
Pairing of \(\mathrm{e}^{-}\)takes place as \(\mathrm{CN}^{-}\)is strong field ligand but has one unpaired electron thus paramagnetic. For \(\left[\mathrm{FeF}_6\right]^{-3}\) As \(\mathrm{F}^{\text {- }}\) is weak field ligand, so no pairing of electron, thus it has five unpaired electron. Therefore paramagnetic.

Hence, the correct answer is option: 'A'.