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Sodium
Notable CharacteristicsLike the other alkali metals, sodium is a soft, light-weight, silvery white, reactive element that is never found unbound in nature. Sodium floats in water and decomposes it releasing hydrogen and forming hydroxide. If ground to a fine enough power, sodium will ignite spontaneously in water. However, this metal does not normally ignite in air below 388 Kelvin.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:
NaK, an alloy of sodium and potassium, 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 Medieval 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% 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 in 1997 but reagent grade (ACS) sodium cost about US$35 per pound in 1990. It is the cheapest of all metals by volume.Isolation (* follow): 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 (NaHCO3), caustic soda (NaOH), Chile saltpeter (NaNO3), 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).PrecautionsIn its powdered form sodium is explosive in water and a poison combined and uncombined with many other elements. This metal should be handled carefully at all times. Sodium cannot be maintained in an inert atmosphere and contact with water and other substances that sodium reacts with should be avoided.
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