Question

For $[Fe{F}_6{]}^{3-}$ and $\left[Fe\right(CN{)}_6{]}^{3-}$ genetic moment of the fluoride complex is expected to be

• A. The same as the magnetic moment of the cyanide complex
• B. Larger than the magnetic moment of the cyanide complex because there are more unpaired electrons in the fluoride complex
• C. Smaller than the magnetic moment of the cyanide complex because there are more unpaired electrons in the fluoride complex
• D. Larger than the magnetic moment of the cyanide complex because there are few unpaired electrons in the fluoride complex

Answer 1

The correct option is B Larger than the magnetic moment of the cyanide complex because there are more unpaired electrons in the fluoride complex

For $[Fe{F}_6{]}^{3-}$ and $\left[Fe\right(CN{)}_6{]}^{3-}$ magnetic moment of the fluoride complex is expected to be larger than the magnetic moment of the cyanide complex because there are more unpaired electrons in the fluoride complex. Higher is the number of unpaired electrons, higher is the magnetic moment.

Cyanide is a strong field ligand. It forms low spin or spin paired complexes. $Fe\left(III\right)$ ion in $\left[Fe\right(CN{)}_6{]}^{3-}$ with $3d^5$ electronic configuration has one unpaired electron.

Fluoride is a weak ligand. It forms high spin or spin free complexes. In $[Fe{F}_6{]}^{3-}$, $Fe\left(III\right)$ has 5 unpaired electrons.