Total number of unpaired electrons present in d orbitals of ${\mathrm{Co}}^{2+}$ and ${\mathrm{Cr}}^{3+}$ is _____.

The number of unpaired electrons present in a given element determines whether the compound is paramagnetic or diamagnetic in nature.

The electronic configuration of $\text{C}{\text{o}}^{2+}$ is $\left[\text{Ar}\right]\text{3}{\text{d}}^{\text{7}}$ and it has one unpaired electron. The electronic configuration of $\text{C}{\text{r}}^{3+}$is ${\text{[Ar]3d}}^3$ and it has 3 unpaired electrons.

Thus, the total number of unpaired electrons that are present in d orbitals of ${\mathrm{Co}}^{2+}$ and ${\mathrm{Cr}}^{3+}$ is 4(1+3).