In: Chemistry
which is the least reactive alkali metal? Based on oxidation potentials why is this unexpected?
Lithium is the least reactive
alkali metals easily lose ns1 electron and thus they have high values of oxidation potential
M + aq —> M+(eq) + e
The standard oxidation potentials of a alkali metals are listed below,
Li Na K Rb Cs
+3.05 +2.71 +2.93 +2.99 +2.99
More is oxidation potential, more is the tendency to get oxidized and thus more powerful is reducing nature in aqueous medium that is why alkali metals liberate H2 from H2O and HCl.
2H2O + 2M —> 2MOH + H2; 2HCl + 2M —> 2MCl + H2
However, an examination of ionization energy for alkali metals reveals that Li should have the minimum tendency to lose electron and thus its reducing nature should be minimum. The greatest reducing nature of Li in aq. medium is accounted due to the maximum hydration energy of Li+ ion.