Question

The d-electron configuration of $C{r}^{2+},M{n}^{2+},F{e}^{2+}\text{and}C{o}^{2+}$ are $d^4$,$d^5$, $d^6$ and $d^7$ respectively. Which one of the following will exhibit minimum paramagnetic behaviour? (Atomic number of Cr=24, Mn=25, Fe =26, Co=27)

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

Answer 1

The correct option is C

$C{o}^{2+}$

The d-electron configuration of $C{r}^{2+},M{n}^{2+},F{e}^{2+}\text{and}C{o}^{2+}$ are $d^4$,$d^5$, $d^6$ and $d^7$ respectivelyAs spin only magnetic moment is $\sqrt{n(n+2)}B.M.$ where n is no. of unpaired electron.
So ion with minimum number of unpaired electron will have minimum paramagnetism.
$C{o}^{2+}$ have minimum paramagnetic behaviour as it has minimum unpaired electron.