Relative stability of $\ce{V^2+}$ and $\ce{V^3+}$ and their Standard Electrode Potential

My book - [NCERT Chemistry for Class XII](https://www.google.com/url?sa=t&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjS9qXh-L_3AhVCUGwGHXfyB1wQFnoECAQQAQ&url=https%3A%2F%2Fncert.nic.in%2Fncerts%2Fl%2Flech108.pdf&usg=AOvVaw1-_qfZQpw5U2hzhzKO-4G7) -Page 218 Contains the following paragraph:


[![enter image description here](https://i.stack.imgur.com/sp1RT.png)](https://i.stack.imgur.com/sp1RT.png)


Initially they mention that the Low value for Standard Electrode Potential of $\ce{Sc^3+/Sc^2+}$ is due to the higher stability of $\ce{Sc^3+}$ which makes sense as it would have a lesser tendency to move to the $+2$ oxidation state.


But later on, they mention that the Lower value of SEP of $\ce{V^3+/V^2+}$ is due to the stability of $\ce{V^2+}$.


I get that the half filled $\ce{t\_{2g}}$ configuration would make $\ce{V^2+}$ more stable but then, shouldn't the SEP value become higher rather than being low? As $\ce{V^3+}$ would have more tendency to move to $\ce{V^2+}$




The $\ce{E^°(M^3+/M^2+)}$ standard electrode potential for $\ce{V}$ has a low negative (that is, a relatively more positive) value. This is attributed to the greater stability of $\ce{V^2+}$ as given in the text.


This can be seen in the $\ce{E^°(M^3+/M^2+)}$ values for $\ce{Ti,V,Cr}$ being $\pu{-0.37, -0.26, -0.41}$ respectively.


The book is not very clear in its meaning of low in this case. Looking at the table of values and comparing the $\ce{E^°(M^3+/M^2+)}$ of nearby elements can help you understand the text better.


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[An independent source](https://chem.libretexts.org/Ancillary_Materials/Reference/Reference_Tables/Electrochemistry_Tables/P1%3A_Standard_Reduction_Potentials_by_Element) gives $-0.37$ for titanium, $-0.26$ for vanadium and $-0.42$ for chromium, showing that vanadium is *relatively high* compared with its immediate neighbors. The book should have said "less negative" rather than "comparatively low".


In any event the effect of half-filling the $t\_{2g}$ orbitals is weak compared with half-filling all of the $3d$ subshell. The above source gives $+1.5$ for manganese versus the aforementioned $-0.42$ for chromium and $+0.77$ for iron. Half-filling the $t\_{2g}$ orbitals alone would have more impact with ligands that have a stronger splitting than water.


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