Solvated electron: Difference between revisions

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A '''solvated electron''' is a [[particle|free]] [[electron]] in (solvated in) a [[solution]], and is the smallest possible [[anion]]. Solvated electrons occur widely although they are often not observed directly. 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).<ref name="c&w">{{cite book |last=Cotton |first=F.A |authorlink= |author2=G. Wilkinson |title=Advanced Inorganic Chemistry |year=1972 |publisher=John Wiley and Sons Inc |___location= |isbn=0-471-17560-9 }}</ref> 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 solvated electron is responsible for a great deal of [[Radiochemistry|radiation chemistry]].

==Properties==

Focusing on ammonia solutions, all of the alkali metals, as well as [[calcium|Ca]], [[strontium|Sr]], [[barium|Ba]], [[europium|Eu]], and [[ytterbium|Yb]] (also [[magnesium|Mg]] using an electrolytic process<ref>C. Combellas, F. Kanoufi, A. Thiebault, ''J. Electroanalytical Chem'' 499(1), 144-151 (2001) {{DOI|10.1016/S0022-0728(00)00504-0}}</ref>), dissolve to give the characteristic blue solutions. Other amines, such as [[methylamine]] and [[ethylamine]], are also suitable solvents.<ref>{{Greenwood&Earnshaw2nd}}</ref>

A lithium ammonia solution at −60&nbsp;°C is saturated at about 16&nbsp;mol% metal (16&nbsp;MPM in the local jargon). When the concentration is increased in this range [[electrical conductivity]] increases from 10⁻² to 10⁴&nbsp;[[ohm]]⁻¹[[Centimetre|cm]]⁻¹ (larger than liquid [[mercury (element)|mercury]]). At around 8&nbsp;MPM, a "transition to the metallic state" (TMS) takes place (also called a "metal to nonmetal transition" (MNMT)). At 4&nbsp;MPM a liquid-liquid phase separation takes place: the less dense gold-color phase becomes immiscible from a more dense blue phase. Above 8 MPM the solution is bronze/gold-colored. In the same concentration range the overall [[density]] decreases by 30%.