Sodium
<p ><b>Sodium</b> (<img src="/c7371551-b1f6-5546-9fe8-4b5f33b3971e.png"/> <a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English" title="Wikipedia:IPA for English" >/</a><a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Key" title="Wikipedia:IPA for English" >ˈsoʊdiəm</a><a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English" title="Wikipedia:IPA for English" >/</a> <a href="http://en.wikipedia.org/wiki/Wikipedia:Pronunciation_respelling_key" title="Wikipedia:Pronunciation respelling key" ><i><b>soh</b>-dee-əm</i></a>) is a <a href="http://en.wikipedia.org/wiki/Chemical_element" title="Chemical element" >chemical element</a> with symbol <b>Na</b> (from <a href="http://en.wikipedia.org/wiki/Latin_language" title="Latin language" class="mw-redirect" >Latin</a>: <i>natrium</i>) and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the <a href="http://en.wikipedia.org/wiki/Alkali_metals" title="Alkali metals" class="mw-redirect" >alkali metals</a>; its only stable <a href="http://en.wikipedia.org/wiki/Isotope" title="Isotope" >isotope</a> is <sup >23</sup>Na. The free metal does not occur in nature, but instead must be prepared from its compounds; it was first isolated by <a href="http://en.wikipedia.org/wiki/Humphry_Davy" title="Humphry Davy" >Humphry Davy</a> in 1807 by the <a href="http://en.wikipedia.org/wiki/Electrolysis" title="Electrolysis" >electrolysis</a>of <a href="http://en.wikipedia.org/wiki/Sodium_hydroxide" title="Sodium hydroxide" >sodium hydroxide</a>. </p>
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Sodium is the sixth most abundant element in the Earth's crust, and exists in numerous minerals such as<a href="http://en.wikipedia.org/wiki/Feldspar" title="Feldspar" >feldspars</a>, <a href="http://en.wikipedia.org/wiki/Sodalite" title="Sodalite" >sodalite</a> and <a href="http://en.wikipedia.org/wiki/Halite" title="Halite" >rock salt</a>. Many salts of sodium are highly water-soluble, and their sodium has been leached by the action of water so that chloride and sodium are the most common dissolved elements by weight in the Earth's bodies of oceanic water.</p>
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Many sodium compounds are useful, such as sodium hydroxide (lye) for <a href="http://en.wikipedia.org/wiki/Soap" title="Soap" >soapmaking</a>, and sodium chloride for use as a deicing agent and a nutrient. </p>
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Sodium is an <a href="http://en.wikipedia.org/wiki/Dietary_mineral" title="Dietary mineral" >essential element</a> for all animals and some plants. In animals, sodium ions are used against <a href="http://en.wikipedia.org/wiki/Potassium" title="Potassium" >potassium</a> ions to <a href="http://en.wikipedia.org/wiki/Na%2B/K%2B-ATPase" title="Na+/K+-ATPase" >build up charges on cell membranes</a>, allowing transmission of nerve impulses when the charge is dissipated. The consequent need of animals for sodium causes it to be classified as a dietary inorganic macro-mineral.</p>