Positive electrode potential of copper My book (NCERT India) says that the electrode potential of metals is decided by the following factors:


Enthalpy of atomisation
Ionisation enthalpy
Hydration enthalpy


It says that the first two require energy while the latter releases energy. That's all good and I can follow till there. But then it provided this table of thermochemical data for 3d series metals (Table 8.4 page 218):



It says that the electrode potential for $\ce{Cu^2+/Cu^1+}$ is positive because the hydration enthalpy does not balance the enthalpy of atomisation and the ionisation enthalpy - which requires energy. By the same logic, simply summing up 1 &amp; 2 (sum of the first and second ionisation enthalpies) &amp; 3 would give a positive value. How is it feasible for any of the there elements to have a negative electrode potential?
The potential as it is given there is vs. standard hydrogen electrode(SHE) which has an arbitrary assigned value of 0.0000V. Through the choice of another reference, it is very easy to make all of those numbers positive or negative. The absolute value of the half cell potential can only be useful in comparison to others. So you could make arguments like Cu has a more positive potential compared to Ni(by 0.59V based on the above numbers), but that is it.