Question

How many of the following has 4 unpaired electrons? $C{r}^{2+},C{o}^{3+},C{u}^{2+},N{i}^{2+}$

Answer 1

Answer: 2

Ions	Electronic configuration	No. of unpaired electrons
$C{r}^{2+}$	$\left[Ar\right]3d^4$	$4$
$C{o}^{3+}$	$\left[Ar\right]3d^6$	$4$
$C{u}^{2+}$	$\left[Ar\right]3d^9$	$1$
$N{i}^{2+}$	$\left[Ar\right]3d^8$	$2$