# Rationalising the trend of standard electrode potentials between the +II and +III oxidation state of first-row transition metals

Trends in standard electrode potentials of d block elements:

An examination ofthe $E^0 (\ce{M^3+}/\ce{M^2+})$ values (Table 8.2) shows the varying trends. The low value for Sc reflects the stability of $\ce{Sc^3+}$ which has a noble gas configuration. The highest value for Zn is due to the removal of an electron from the stable $\mathrm d^{10}$ configuration of $\ce{Zn^2+}$. The comparatively high value for Mn shows that $\ce{Mn^2+}\ (\mathrm d^5)$ is particularly stable, whereas comparatively low value for Fe shows the extra stability of $\ce{Fe^3+}\ (\mathrm d^5)$.The comparatively low value for V is related to the stability of $\ce{V^2+}$ half-filled $\mathrm{t_{2g}}$ level, Unit 9).

It says that low value of Sc is due to stability of $\ce{Sc^3+}$. At the same time, low value of V is due to stability of $\ce{V^2+}$. Don't these statements contradict each other? If not, could someone please explain this paragraph in an easier way? I m not able to understand it.

• chemistry.stackexchange.com/a/66172/9961 – Mithoron Nov 5 '17 at 14:31
• Yes, those statements contradict each other, so you might be better off ditching this book. My take on the matter is already linked in the comment above. – orthocresol Nov 5 '17 at 15:06
• It is a standard ncert book – user166465 Nov 5 '17 at 15:07
• Here low value of 'V' is low value in magnitude(as it is negative). Some chemistry text don't bother to write clearly in these type of cases. – Shivam Agarwal Mar 14 '18 at 15:25