<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 occur in water and other solvents; in fact, 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 . </P> <P> The solvated electron is responsible for a great deal of radiation chemistry . </P>

The solution of alkali metal in liquid nh3 is blue coloured due to