The \(\text{E}^\circ\) value for the \(\text{Mn}^{3+}\,/\,\text{Mn}^{2+}\) couple is more positive than that of \(\text{Cr}^{3+}\,/\,\text{Cr}^{2+}\) or \(\text{Fe}^{3+}\,/\,\text{Fe}^{2+}\) due to change of: