Question

The ratio of magnetic moments of $Fe\left(III\right)$ and $Co\left(II\right)$ is:

• A. $\sqrt{5}:\sqrt{7}$
• B. $\sqrt{35}:\sqrt{15}$
• C. $7:3$
• D. $\sqrt{24}:\sqrt{15}$

Answer 1

The correct option is B $\sqrt{35}:\sqrt{15}$

Electronic configuration of $Fe\left(III\right)-\left[Ar\right]3d^5;$ unpaired electrons = 5;
$\therefore$ Magnetic moment $=\sqrt{5(5+2)}BM$ $=\sqrt{35}BM$
Electronic configuration of $Co\left(II\right)-\left[Ar\right]3d^7;$ unpaired electrons = 3;
magnetic moment $=\sqrt{3\times (3+2)}BM$ $=\sqrt{15}BM$
$\therefore Ratio=\frac{\sqrt{35}}{\sqrt{15}}$