Solvated electron

For alkali metals in liquid ammonia, the solution is blue when dilute and copper-colored when more concentrated (> 3 molar).

The blue colour of the solution is due to ammoniated electrons, which absorb energy in the visible region of light.

The reaction is reversible: evaporation of the ammonia solution produces a film of metallic sodium.

Alkali metals also dissolve in some small primary amines, such as methylamine and ethylamine[7] and hexamethylphosphoramide, forming blue solutions.

Tetrahydrofuran (THF) dissolves alkali metal, but a Birch reduction (see § Applications) analogue does not proceed without a diamine ligand.

This implies their possible existence in the upper atmosphere of Earth and involvement in nucleation and aerosol formation.

[12] It's standard electrode potential value is -2.88 V.[13] The equivalent conductivity of 177 Mho cm2 is similar to that of hydroxide ion.

[16] Solvated electrons are involved in electrode processes, a broad area with many technical applications (electrosynthesis, electroplating, electrowinning).

[17] An example of this is the intercalation of graphite with potassium and ammonia, which is then exfoliated by spontaneous dissolution in THF to produce a graphenide solution.

[26] They noted based on absorption spectra that different metals and different solvents (methylamine, ethylamine) produce the same blue color, attributed to a common species, the solvated electron.

Photos of two solutions in round-bottom flasks surrounded by dry ice; one solution is dark blue, the other golden.
Solutions obtained by dissolution of lithium in liquid ammonia. The solution at the top has a dark blue color and the lower one a golden color. The colors are characteristic of solvated electrons at electronically insulating and metallic concentrations, respectively.