Alkalide

Alkali metals form many well-known stable salts. Sodium chloride (common table salt), , illustrates the usual role of an alkali metal such as sodium. In the empirical formula for this ionic compound, the positively charged sodium ion is balanced by a negatively charged chloride ion. The traditional explanation for stable 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. ==Nomenclature and known cases==

There are known alkalides for some of the alkali metals: • Sodide or natride, • Potasside or kalide, • Rubidide, • Caeside, Alkalides of the other alkali metals have not yet been discovered: • Lithide, • Francide, ==Examples==

Normally, alkalides are thermally labile due to the high reactivity of the alkalide anion, which is theoretically able to break most covalent bonds including the carbon–oxygen bonds in a typical cryptand. The introduction of a special cryptand ligand containing amines instead of ether linkages has allowed the isolation of kalides and natrides that are stable at room temperature. Several alkalides have been synthesized: • A compound in which hydrogen ions are encapsulated by adamanzane, known as hydrogen natride or "inverse sodium hydride" (hydrogen sodide or hydrogen natride ), has been observed. • Sodium-crypt natride, [Na(cryptand[2.2.2])]+Na−, has been observed. This salt contains both and . The cryptand isolates and stabilizes the , preventing it from being reduced by the . • Barium azacryptand-sodide, Ba2+[H5Azacryptand[2.2.2−Na−⋅2CH3NH2, has been synthesized. • Anionic sodium dimers have been observed. ==References==