Definition: A metallic element, atomic no. 11, atomic wt. 22.989768; an alkali metal oxidizing readily in air or water; its salts are found in natural biologic systems and are extensively used in medicine and industry. The sodium ion is the most plentiful extracellular ion in the body. For organic sodium salts not listed here, see under the name of the organic acid portion.
[Mod. L. fr. soda]