<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>
the solution of alkali metal in liquid nh3 is blue coloured due to
the presence of solvated electrons