Question

The stable oxidation state of Cr in the presence of a weak field ligand is:

• A. $C{r}^{2+}$
• B. $C{r}^{3+}$
• C. $C{r}^{4+}$
• D. $C{r}^{6+}$

Answer 1

The correct option is B $C{r}^{3+}$

More the number of electrons in the $t_{2g}$ orbitals and less the number of electrons in the $e_g$ orbitals, more will be the CFSE and greater will be the stability.

$C{r}^{3+}$ is the most stable because, in aqueous solution, it has a higher CFSE on account of the half filled $t_{2g}^3$ energy level of the 3d orbitals in octahedral spliting.

$C{r}^{2+}$ is less stable because, it has one electron in the $e_g$ orbital.