Question

The substances which contain species with unpaired electrons in their orbitals behave as paramagnetic substances. Such substances are weakly attracted by the magnetic field. The paramagnetism is expressed in terms of the magnetic moment. The magnetic moment is related to the number of unpaired electrons according to the following relation:

Magnetic moment, $\mu =\sqrt{n(n+2)}BM$ where, $n=$ number of unpaired electrons.
$BM$ stands for Bohr magneton, a unit of the magnetic moment.
$1BM=\frac{eh}{4\pi mc}=9.27\times {10}^{-24}{Am}^2$ or $J{T}^{-1}$

An ion of a $d$-block element has a magnetic moment $5.92BM$. Select the ion among the following

• A. ${Zn}^{2+}$
• B. ${Sc}^{3+}$
• C. ${Mn}^{2+}$
• D. ${Cr}^{3+}$

Answer 1

The correct option is C ${Mn}^{2+}$

The magnetic moment of 5.92 BM corresponds to 5 unpaired electrons.
$\mu =\sqrt{n(n+2)}BM$
$5.92=\sqrt{n(n+2)}BM$
$35=n(n+2)$
$n=5$
The ion is $M{n}^{2+}$ with electronic configuration $3d^5$ and 5 unpaired electrons.
$Z{n}^{2+}3d^{10}0$ unpaired electrons.
$S{c}^{3+}3d^{0}0$ unpaired electrons.
$C{r}^{3+}3d^{3}3$ unpaired electrons.