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Sodium |
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Sodium Sodium is the chemical element in the periodic table that has the symbol Na (Natrium in Latin) and atom number 11. Sodium is a soft, waxy, silvery reactive metal belonging to the alkali metals that is abundant in natural compounds (especially halite). Notable characteristicsLike the other alkali metals, sodium is a soft, light-weight, silvery white, reactive element that is never found as a pure element in nature. Sodium floats in water, as well as decomposing it to release hydrogen gas and hydroxide ions. If ground to a fine enough powder, sodium will ignite spontaneously in water. However, it does not normally ignite in air below 388 kelvins. ApplicationsSodium in its metallic form is an essential component in the making of esters and in the manufacture of organic compounds. This alkali metal is also a component of sodium chloride (NaCl) which is vital to life. Other uses: NaCl, an compound of sodium ions and chloride ions, is an important heat transfer material. HistorySodium (English, soda) has long been recognized in compounds, but was not isolated until 1807 by Sir Humphry Davy through the electrolysis of caustic soda. In medieval Europe a compound of sodium with the Latin name of sodanum was used as a headache remedy. Sodium's symbol, Na, comes for the neo-Latin name for a common sodium compound named natrium, which comes from the Greek nítron, a kind of natural salt. OccurrenceSodium is relatively abundant in stars and the D spectral lines of this element are among the most prominent in star light. Sodium makes up about 2.6% by weight of the Earth's crust making it the fourth most abundant element overall and the most abundant alkali metal. It is now produced commercially through the electrolysis of completely dry fused sodium chloride. This method is less expensive than the previous method of electrolyzing sodium hydroxide. Metallic sodium cost about 15 to 20 US cents per pound (US$0.30/kg to US$0.45/kg) in 1997 but reagent grade (ACS) sodium cost about US$35 per pound (US$75/kg) in 1990. It is the cheapest of all metals by volume. CompoundsSodium chloride, better known as common salt, is the most common compound of sodium, but sodium occurs in many other minerals, such as amphibole, cryolite, halite, soda niter, zeolite, etc. Sodium compounds are important to the chemical, glass, metal, paper, petroleum, soap, and textile industries. Soap is generally a sodium salt of certain fatty acids. The sodium compounds that are the most important to industry are common salt (NaCl), soda ash (Na2CO3), baking soda (NaHCOCO3), caustic soda (NaOH), Chile saltpeter (NaNOO3), di- and tri-sodium phosphates, sodium thiosulfate (hypo, Na2S2O3 · 5H2O), and borax (Na2B4O7 · 10H2O). IsotopesThere are thirteen isotopes of sodium that have been recognized. The only stable isotope is Na-23. Sodium has two radioactive cosmogenic isotopes (Na-22, half-life = 2.605 years; Na-24, half-life ≈ 15 hours). PrecautionsSodium's powdered form is highly explosive in water and a poison combined and uncombined with many other elements. This metal should be handled carefully at all times. Sodium must be stored either in an inert atmosphere, or under mineral oil. Physiology and Na ionsSodium ions play a diverse role in many physiological processes. Excitable cells, for example, rely on the entry of Na+ to cause a depolarization. An example of this is signal transduction in the human central nervous system . ReferencesExternal links
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