Question

A complex of certain metal has the magnetic moment of $4.89BM$ whereas another complex of the same metal with same oxidation state has zero magnetic moment. The metal ion could be :

• A. $C{o}^{2+}$
• B. $M{n}^{2+}$
• C. $F{e}^{2+}$
• D. $F{e}^{3+}$

Answer 1

The correct option is C $F{e}^{2+}$

(magnetic moment $\mu =\sqrt{n}(n+2)$ where n is no. of unpaired electron).

In high spin complex, metal ion has 4 unpaired electron and

in low spin complex it has zero unpaired electron.

So ion is $F{e}^{+2},d^6{t}_{2g}^4{e}_g^2$ high spin, 4 unpaired electron.

$F{e}^{+2},d^6{t}_{2g}^6{e}_g^0$ low spin, zero unpaired electron.

So ion is $F{e}^{+2}$.

Hence option C is correct.