<P> A solvated electron is a free electron in (solvated in) a solution, and is the smallest possible anion . Solvated electrons occur widely, although it is difficult to observe them directly since their lifetimes are so short . The deep color of solutions of alkali metals in ammonia arises from the presence of solvated electrons: blue when dilute and copper - colored when more concentrated (> 3 molar). Classically, discussions of solvated electrons focus on their solutions in ammonia, which are stable for days, but solvated electrons also occur in water and other solvents--in fact, in any solvent that mediates outer - sphere electron transfer . The real hydration energy of the solvated electron can be estimated by using the hydration energy of proton in water combined with kinetic data from pulse radiolysis experiments . The solvated electron forms an acid - base pair with atomic hydrogen . </P> <P> The solvated electron is responsible for a great deal of radiation chemistry . </P> <P> Alkali metals dissolve in liquid ammonia giving deep blue solutions which are conducting in nature . The blue colour of the solution is due to ammoniated electrons which absorb energy in the visible region of light . Alkali metals also dissolve in hexamethylphosphoramide, forming blue solutions . </P>

The solution of sodium in ammonia blue in colour