碱金属
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 is 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.