Question

Which of the following complex has zero magnetic moment (spin only)?

• A. $\left[\mathrm{Ni}\left(\mathrm{NH}_3\right)_6\right] \mathrm{Cl}_2$
• B. $N a_{3}\left[\right.F e F_{6}\left]\right.$
• C. $\left[\mathrm{Cr}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right] \mathrm{SO}_4$
• D. $K_{4}\left[\right.Fe\left(C N\right)_{6}\left]\right.$

Answer 1

Answer: (D)

Ferrocyanide ion $\left(\left[F e \left(C N\right)_{6}\right]\right)^{4 -}$ is diamagnetic in nature hence $K_{4}\left[\right.Fe\left(C N\right)_{6}\left]\right.$ complex has zero magnetic moment.

$\text{Fe}$ atom $\text{3d}^{\text{6}} \, \text{4s}^{\text{2}} \, \text{4p}^{\text{0}}$

$\text{Fe} \, \text{(II)}$

$\text{d}^{\text{2}} \, \text{sp}^{\text{3}}$ hybridisation