Alkalide

An alkalide is a chemical compound in which alkali metal atoms are anions (negative ions) with a charge or oxidation state of –1. Until the first discovery of alkalides in the 1970s, alkali metals were only known to appear in salts only as cations (positive ions) with a charge or oxidation state of +1. These types of compounds are of theoretical interest due to their unusual stoichiometry and low ionization potentials. Alkalide compounds are chemically related to the electrides, salts in which trapped electrons are effectively the anions. An alkalide is a chemical compound in which alkali metal atoms are anions (negative ions) with a charge or oxidation state of –1. Until the first discovery of alkalides in the 1970s, alkali metals were only known to appear in salts only as cations (positive ions) with a charge or oxidation state of +1. These types of compounds are of theoretical interest due to their unusual stoichiometry and low ionization potentials. Alkalide compounds are chemically related to the electrides, salts in which trapped electrons are effectively the anions. Alkali metals form many well-known stable salts. Sodium chloride (common table salt), Na+Cl−, illustrates the usual role of an alkali metal such as sodium. In the empirical formula for this ionic compound, the positively charged sodium ion balanced by a negatively charged chloride ion. The traditional explanation for stable Na+ is that the loss of one electron from elemental sodium to produce a cation with charge of +1 produces a stable closed-shell electron configuration.