Standard Electrode Potentials and Metallurgy : The method employed for extracting a metal from its ore depends on the nature of the metal, that of the ore and may be related to the position of the metal in the electrochemical series. In general, metals with reduction potential less than - 0.5 volt yield compounds which are very difficult to reduce. Such metals are isolated by electrolysis. On the other hand noble metals with reduction potential + 0.5 volt form easily reducible compounds.
The standard electrode potential of a metal is a measure of its tendency to go into solution as hydrated ion. On the other hand, in metallurgical extractions we generally come across ores which are to be reduced to the metallic state. Thus, it maybe said that a metal higher up in the electrochemical series should be more difficult to reduce to metallic form. As we move down, the reduction becomes more and more easy. However, it must be borne in mind that this is a very general statement and cannot be strictly applied because metals are seldom extracted from aqueous solutions.
Energy Factors and Electrode Potentials — The heat of sublimation (S) of solid metal, the ionization energy (I) of gaseous metal atom and the heat of hydration (H) of gaseous ion are the contributory factors towards electrode potential (E). These factors may be consolidated in a Born-Haber type of cycle.
 

$\text{ Thus, }\mathrm{E}=+\mathrm{S}+\mathrm{I}-\mathrm{H}$
Sublimation and ionization energies are positive because energy is supplied while hydration energy is an exothermic process. As expected, ionization energies of alkali metals follow the trend : Li>Na>K>Rb>Cs
It means Li has the least tendency to lose electron among alkali metals. However, from electrochemical series we find that lithium is the most reducing in character (E° for a ${\mathrm{Li}}^{+}/\mathrm{Li}$ = -3.05 volt). The anomalous behaviour of Li is understandable from the fact that heat of hydration of its ion is highest because of small size. The contribution of this hydration factor towards electrode potential makes Li even more reducing than Na or K.