Difference between revisions of "Sodium" - New World Encyclopedia

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{{Elementbox_header | number=11 | symbol=Na | name=sodium | left=[[neon]] | right=[[magnesium]] | above=[[lithium|Li]] | below=[[potassium|K]] | color1=#ff6666 | color2=black }}
 
{{Elementbox_header | number=11 | symbol=Na | name=sodium | left=[[neon]] | right=[[magnesium]] | above=[[lithium|Li]] | below=[[potassium|K]] | color1=#ff6666 | color2=black }}
 
{{Elementbox_series | [[alkali metal]]s }}
 
{{Elementbox_series | [[alkali metal]]s }}
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:''For sodium in the diet, see [[Edible salt]].''
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'''Sodium''' (chemical symbol '''Na''', [[atomic number]] 11) is a member of a group of [[chemical element]]s known as alkali [[metal]]s. Silvery in color, it is soft, waxy, and lightweight. It is highly reactive, oxidizing rapidly in air and reacting violently with [[water]] to produce the alkali sodium hydroxide and [[hydrogen]] gas. Given its reactivity, sodium is not found as a free metal in nature but is bound to other elements in the form of compounds. It also occurs as [[Ion (physics)|cations]] in seawater.
  
'''Sodium'''  (chemical symbol '''Na''', [[atomic number]] 11) is a member of a group of [[chemical element]]s known as alkali [[metal]]s. Soft and waxy, it is silvery in color and highly reactive. It oxidizes rapidly in air. It reacts violently with [[water]] to produce the alkali sodium hydroxide and [[hydrogen]] gas. In nature, it is bound to other elements in the form of compounds, or it occurs as [[Ion (physics)|cations]] in solution.
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Sodium metal can be used to isolate some other metals from their compounds, smoothen metal surfaces, and manufacture several compounds. Sodium vapor lamps provide bright illumination at low cost. An alloy of sodium and [[potassium]] (NaK) is a heat-transfer medium and a chemical reducing agent.
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{{toc}}
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Moreover, the compounds of sodium have numerous applications. Common [[salt]], or table salt, is sodium chloride, widely used as a food flavoring. It provides the body with sodium ions, which are essential nutrients, but excessive amounts are harmful for health. It is also an agent for de-icing highways in the winter. Sodium bicarbonate is an antacid, a leavening agent in baking, and an ingredient in some forms of toothpaste. Sodium hydroxide is a powerful chemical base, but sodium bicarbonate and sodium carbonate are also used to raise the alkalinity of solutions. The carbonate, chloride, and hydroxide of sodium are important industrial chemicals, used in the manufacture of [[glass]], pulp and [[paper]], textiles, soaps and detergents, and other sodium salts.
  
The ions, alloys, and compounds of potassium have a wide range of applications. Sodium ions are essential nutrients for living organisms and are found in seawater and most [[soil]] types.
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== Isolation and etymology ==
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Compounds of sodium have long been known. The [[metal]] itself was first isolated in 1807, when Sir [[Humphry Davy]] carried out the [[electrolysis]] of [[caustic soda]] (sodium hydroxide). Sodium was deposited on the cathode.
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The name ''sodium'' comes from the [[English language|English]] word, ''soda''. The symbol for sodium, Na, comes from the [[neo-Latin]] name for a common sodium compound called ''natrium''. That name in turn comes from the [[Greek language|Greek]] ''nítron'', a kind of natural [[salt]]. In medieval [[Europe]], a compound of sodium with the [[Latin]] name ''sodanum'' was used as a [[headache]] remedy.
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== Occurrence and production ==
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Sodium is the most abundant alkali metal and makes up about 2.6 percent by weight of the [[Earth]]'s crust. Naturally occurring sodium is bound to other elements in many minerals. The most common sodium-containing mineral is [[halite]] (or rock salt), chemically known as sodium chloride. Other [[mineral]]s that contain sodium include [[cryolite]] (sodium aluminum fluoride), soda ash (sodium carbonate), and soda niter (or Chile saltpeter, sodium nitrate), as well as several members of the amphibole and zeolite groups of minerals.
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Sodium is relatively abundant in [[star]]s. Its spectral lines, known as the sodium D lines, are among the most prominent in starlight.
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At the end of the nineteenth century, sodium was chemically prepared by heating [[sodium carbonate]] with [[carbon]] to 1,100 °C. The reaction may be written as follows.
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:Na<sub>2</sub>CO<sub>3</sub> (liquid) + 2 C (solid, coke) &rarr; 2 Na (vapor) + 3 CO (gas).
  
*''Natrium'' in [[Latin]]).  
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Sodium is now produced commercially through the [[electrolysis]] of fused (liquefied) [[sodium chloride]]. In this process, known as the Downs process, [[calcium chloride]] is mixed with the sodium chloride to lower the [[melting point]] below 600 &deg;C. Sodium, but not [[calcium]], is deposited on the cathode. This method is less expensive than the earlier method of electrolyzing [[sodium hydroxide]].
* it is abundant in natural compounds (especially [[halite]]).
 
It is highly reactive, burns with a yellow flame, reacts violently with [[water]] and [[oxidation|oxidizes]] in air necessitating storage in an inert environment.
 
  
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== Notable characteristics ==
  
[Potassium is a member of a group of [[chemical element]]s known as alkali [[metal]]s. It is a soft metal and is silvery white when freshly cut, but it tarnishes rapidly on exposure to [[Earth's atmosphere|air]]. Less dense than water, it is the second least dense metal after [[lithium]]. It reacts violently with [[water]] to produce the alkali potassium hydroxide and [[hydrogen]] gas.]
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[[Image:Flametest—Na.swn.jpg|thumb|left|200px|The flame test for sodium displays a brilliantly bright yellow emission due to the so-called "sodium D lines" at 588.9950 and 589.5924 nanometers.]]
  
[The ions, alloys, and compounds of potassium have a wide range of applications. Potassium ions are essential nutrients for living organisms and are found in seawater and most [[soil]] types. The hydroxide of potassium is an important industrial chemical, and the chloride, sulfate, and carbonate are used in [[fertilizer]]s. Potassium nitrate is used in [[gunpowder]], the carbonate is valuable for the manufacture of [[glass]], and the superoxide is a source of oxygen in portable respiratory systems.]
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As an [[alkali metal]], sodium lies in group 1 (former group 1A) of the [[periodic table]], between [[lithium]] and [[potassium]]. In addition, it is at the beginning of period 3, situated just before [[magnesium]].
  
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Like the other [[alkali metal]]s, sodium metal is a soft, lightweight, reactive metal. Owing to its extreme reactivity, its occurrence in nature takes the form of compounds, never as the pure element. Sodium metal floats on [[water]] and reacts violently with it, releasing heat, [[hydrogen]] gas, and caustic [[sodium hydroxide]] solution. When sodium or its compounds are burned in a flame, they give off a distinct yellow color, corresponding to two main spectral lines&mdash;the "sodium D lines" at wavelengths 588.9950 and 589.5924 nanometers.
  
== Isolation and etymology ==
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In 1860, in their paper "Chemical Analysis by Observation of Spectra" in the scientific journal ''Annalen der Physik und der Chemie'', [[Gustav Kirchhoff]] and [[Robert Bunsen]] reported: "In a corner of our 60 cu.m. (cubic meter) room farthest away from the apparatus, we exploded 3 mg. (milligrams) of sodium chlorate with milk sugar, while observing the nonluminous flame before the slit. After a few minutes, the flame gradually turned yellow and showed a strong sodium line that disappeared only after 10 minutes. From the weight of the sodium salt and the volume of air in the room, we easily calculate that one part by weight of air could not contain more than 1/20 millionth weight of sodium."
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Under extreme pressure, sodium departs from standard rules for changing to a liquid state. Most materials need more [[thermal energy]] to melt under high pressure than they do at normal atmospheric pressure. This is because the molecules are packed closer together and have less room to move. At a pressure of 30 gigapascals (300,000 times sea-level atmospheric pressure), the melting temperature of sodium begins to drop. At around 100 gigapascals, sodium melts near room temperature.
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A possible explanation for the aberrant behavior of sodium is that this element has one unpaired [[electron]] (in the outermost shell) that is pushed closer to the other ten electrons when placed under pressure, forcing interactions that are normally absent. While under pressure, solid sodium assumes several odd [[crystal]] structures, suggesting that the liquid might have unusual properties such as [[superconductivity]] or [[superfluidity]] (Gregoryanz et al. 2005).
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=== Isotopes ===
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There are 13 known [[isotope]]s of sodium, of which the only stable one is <sup>23</sup>Na. Sodium has two [[Radioactivity|radioactive]] [[cosmogenic]] isotopes&mdash;that is, isotopes produced when high-energy cosmic rays interact with the nuclei of sodium atoms. They are <sup>22</sup>Na, with a [[half-life]] of 2.605 years, and <sup>24</sup>Na, with a half-life of about 15 hours.
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Exposure to high levels of neutron radiation (such as from a nuclear reactor accident) converts some of the stable <sup>23</sup>Na in human blood plasma to <sup>24</sup>Na. By measuring the concentration of the latter isotope, the neutron radiation dosage to the victim can be computed.
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== Precautions ==
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Sodium metal should be handled carefully at all times. It is highly explosive in water and is a poison when uncombined with other elements. The powdered form may burn spontaneously in air or oxygen. For these reasons, sodium must be stored either in an inert atmosphere or under a liquid hydrocarbon such as mineral oil or [[kerosene]].
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== Compounds ==
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=== Sodium bicarbonate ===
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Sodium bicarbonate (NaHCO<sub>3</sub>) is also known as sodium hydrogen carbonate, or bicarbonate of soda, or baking soda. It is a soluble white compound, with a slight [[alkaline]] taste resembling that of [[sodium carbonate]]. It is found in many [[mineral spring]]s and also produced artificially.
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When exposed to an [[acid]], sodium bicarbonate releases [[carbon dioxide]] and [[water]]. The reaction is as follows.
  
Compounds of sodium have long been known. The metal itself was first isolated in 1807, when Sir [[Humphry Davy]] carried out the [[electrolysis]] of [[caustic soda]]* (sodium hydroxide). Sodium was deposited on the cathode.
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: NaHCO<sub>3</sub> + HCl Å® NaCl + H<sub>2</sub>O + CO<sub>2</sub> (gas)
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: NaHCO<sub>3</sub> + CH<sub>3</sub>COOH Å® NaCH<sub>3</sub>COO + H<sub>2</sub>O + CO<sub>2</sub> (gas)
  
The name ''sodium'' comes from the [[English language|English]] word, ''soda''. The symbol for sodium, Na, comes from the [[neo-Latin]]* name for a common sodium compound called ''natrium''. That name in turn comes from the [[Greek language|Greek]] ''nítron'', a kind of natural [[salt]]. In medieval [[Europe]], a compound of sodium with the [[Latin]] name ''sodanum'' was used as a [[headache]] remedy.
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Above 60°C, sodium bicarbonate gradually decomposes into [[sodium carbonate]], [[water]], and [[carbon dioxide]], and at 200°C it is completely decomposed into sodium carbonate:
  
== Occurrence and production ==
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: 2NaHCO<sub>3</sub> Å® Na<sub>2</sub>CO<sub>3</sub> + H<sub>2</sub>O + CO<sub>2</sub>
  
Sodium is the fourth most abundant element on our planet and the most abundant alkali metal. It makes up about 2.6% by weight of the [[Earth]]'s crust. Naturally occurring sodium is bound to other elements in many minerals. A common mineral is halite, or rock salt, which corresponds to sodium chloride, the most common compound of sodium. Other [[mineral]]s that contain sodium include albite, arfvedsonite, cryolite, glaucophane, hauyne, natron, sodalite, and soda niter.
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=== Sodium carbonate ===
  
Sodium is relatively abundant in [[star]]s. Its spectral lines, known as the sodium D lines, are among the most prominent in starlight.
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Sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>), also known as washing soda or soda ash, is a sodium [[salt]] of carbonic acid (H<sub>2</sub>CO<sub>3</sub>). It most commonly occurs as a [[crystal]]line heptahydrate (Na<sub>2</sub>CO<sub>3</sub>.7H<sub>2</sub>O) that readily loses water from the crystals to form a white powder, the monohydrate (Na<sub>2</sub>CO<sub>3</sub>.H<sub>2</sub>O). It has a cooling, [[alkaline]] taste and can be extracted from the ashes of many [[plant]]s. It is produced artificially in large quantities from [[common salt]] (sodium chloride).
  
At the end of the nineteenth century, sodium was chemically prepared by heating [[sodium carbonate]]* with [[carbon]] to 1,100 &deg;C. The reaction may be written as follows.
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Although sodium carbonate is soluble in [[water]], it can occur naturally in arid regions, especially in the [[mineral]] deposits (''evaporites'') formed when seasonal [[lake]]s evaporate. Deposits of the mineral [[natron]], a combination of sodium carbonate and sodium bicarbonate, have been mined from dry lake bottoms in [[Egypt]] since ancient times, when [[natron]] was used in the preparation of [[mummy|mummies]] and in the early manufacture of glass.
:Na<sub>2</sub>CO<sub>3</sub> (liquid) + 2 C (solid, coke) &rarr; 2 Na (vapor) + 3 CO (gas).
 
  
Sodium is now produced commercially through the [[electrolysis]] of fused (liquefied) [[sodium chloride]]*. In this process, known as the Downs process, [[calcium chloride]]* is mixed with the sodium chloride to lower the [[melting point]] below 600 &deg;C. Sodium, but not [[calcium]], is deposited on the cathode. This method is less expensive than the earlier method of electrolyzing [[sodium hydroxide]]*.
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=== Sodium chloride ===
  
== Notable characteristics ==
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Sodium chloride, also known as common salt or table salt, is a compound with the [[chemical formula]] NaCl. It is found in large quantities in seawater and as the mineral [[halite]] or rock salt. It is the [[salt]] most responsible for the salinity of the [[ocean]]s. It is produced by the evaporation of seawater, brine wells, and salt lakes, and by mining rock salt.
  
[[Image:Flametest—Na.swn.jpg|thumb|left|200px|The flame test for sodium displays a brilliantly bright yellow emission due to the so called "sodium D-lines" at 588.9950 and 589.5924 nanometers.]]
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This salt is essential to [[life]] on [[Earth]]. It is present (at various concentrations) in most biological tissues and body fluids. The concentration of sodium ions in the [[blood]] is directly related to the regulation of safe body-fluid levels. The propagation of [[nerve impulse]]s (by "signal transduction") is regulated by sodium [[Ion (physics)|ion]]s. Humans are unusual among [[primate]]s in secreting large amounts of salt by [[sweating]]. On the other hand, too much salt in the body is bad for health.
  
Like the other [[alkali metal]]s, sodium metal is a soft, light-weight, silvery white, reactive metal. Owing to its extreme reactivity, in nature it occurs only combined into compounds, and never as a pure elemental metal. Sodium metal floats on [[water]], and reacts violently with it releasing heat, flammable [[hydrogen]] gas and caustic [[sodium hydroxide]] solution.
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As the main ingredient in [[edible salt]], sodium chloride is commonly used as a [[condiment]] and food [[preservative]]. Its usefulness as a food preservative helped eliminate human dependency on the seasonal availability of food and allowed travel over long distances. By the [[Middle Ages]], caravans consisting of as many as 40,000 [[camel]]s traversed four hundred miles of the [[Sahara]] bearing salt, sometimes trading it for [[Slavery|slaves]].
  
In 1860, in their paper "Chemical Analysis by Observation of Spectra" published in the scientific journal ''Annalen der Physik und der Chemie'', [[Gustav Kirchhoff]]* and [[Robert Bunsen]]* reported: "In a corner of our 60 cu.m. (cubic meter) room farthest away from the apparatus, we exploded 3 mg. (milligrams) of sodium chlorate with milk sugar, while observing the nonluminous flame before the slit. After a few minutes, the flame gradually turned yellow and showed a strong sodium line that disappeared only after 10 minutes. From the weight of the sodium salt and the volume of air in the room, we easily calculate that one part by weight of air could not contain more than 1/20 millionth weight of sodium."
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There are many references to common salt in the [[Bible]]. A familiar story is about Lot's wife, who was turned into a pillar of salt when she disobeyed the [[angel]]s and looked back at the wicked city of [[Sodom]] ([[Genesis]] 19:26). In the [[Sermon on the Mount]], [[Jesus]] told his followers that they were the "salt of the earth," referring to their internal, spiritual
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flavoring that they needed to distribute to others. Furthermore, in several religious traditions, common salt is used to bless (or spiritually purify) people, places, and things. This usage is probably based on the clean appearance of pure salt, its chemical stability, and its value for living things.
  
Sodium ions are necessary for regulation of blood and body fluids, transmission of nerve impulses, heart activity, and certain metabolic functions. It is widely considered that most people consume more than is needed, in the form of [[sodium chloride]], or table salt, and that this can have a negative effect on the health.
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=== Sodium hydroxide ===
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Sodium hydroxide (NaOH), also known as lye or caustic soda, is a strong chemical base, widely used in chemical laboratories and in industry. The pure substance is a white solid, available in pellets, flakes, and granules, and also as a 50 percent saturated solution. It readily absorbs [[water]] and [[carbon dioxide]] from the air, so it should be stored in an airtight container.
  
Under extreme pressure, sodium departs from standard rules for changing to a liquid state. Most materials need more [[thermal energy]] to melt under pressure than they do at normal atmospheric pressure. This is because the molecules are packed closer together and have less room to move.
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This substance is very soluble in water, and the process of dissolving it liberates heat. It also dissolves in other polar solvents such as [[ethanol]] and [[methanol]], but it is insoluble in nonpolar solvents such as diethyl ether.
At a pressure of 30 [[gigapascal]]s (300,000 times sea level atmospheric pressure), the melting temperature of sodium begins to drop. At around 100 gigapascals, sodium will melt near room temperature.
 
  
A possible explanation for the aberrant behavior of sodium is that this element has one free [[electron]] that is pushed closer to the other 10 electrons when placed under pressure, forcing interactions that are not normally present. While under pressure, solid sodium assumes several odd [[crystal structure]]s suggesting that the liquid might have unusual properties such as [[Superconductivity|superconduction]] or [[Superfluid|superfluidity]]. (Gregoryanz, ''et al.'', 2005)
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Gloves and eye protection should be worn when using sodium hydroxide, because it can cause [[chemical burn]]s, injury or scarring, and [[blindness]]. An apron of polyvinyl chloride is also recommended when concentrated solutions or the solid form are used. It should be stored well away from strong acids such as sulfuric acid.
  
== Isotopes ==
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Caustic soda is produced by the [[electrolysis]] of an aqueous solution of sodium chloride. It builds up at the [[cathode]], where water is reduced to hydrogen gas and [[hydroxide]] ions. The process, called the "chloralkali process," also produces [[chlorine]].
  
Thirteen [[isotope]]s of sodium have been recognized. The only stable isotope is <sup>23</sup>Na. Sodium has two [[radioactive]] [[cosmogenic]] isotopes (<sup>22</sup>Na, [[half-life]] = 2.605 years; and <sup>24</sup>Na, half-life &asymp; 15 hours).
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Sodium hydroxide is an ionic compound, made up of sodium ions and [[hydroxide]] ions. The hydroxide ion makes sodium hydroxide a strong base, which reacts with acids to form [[water]] and the corresponding salts. For example, with [[hydrochloric acid]], sodium chloride is formed:
  
Acute neutron radiation exposure (e.g., from a nuclear [[criticality accident]]) converts some of the stable <sup>23</sup>Na in human blood plasma to <sup>24</sup>Na. By measuring the concentration of this isotope, the neutron radiation dosage to the victim can be computed.
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:NaOH(aq) + HCl(aq) Å® NaCl(aq) + H<sub>2</sub>O(l)
  
== Applications ==
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Such [[acid-base reaction]]s can also be used for [[titration]]s, and this is a common way for measuring the concentration of acids. Related to this is the reaction of sodium hydroxide with acidic oxides such as [[carbon dioxide]] (CO<sub>2</sub>) and [[sulfur dioxide]] (SO<sub>2</sub>). Such reactions are often used to "scrub" harmful acidic gases (like SO<sub>2</sub> and H<sub>2</sub>S) and prevent their release into the atmosphere.
[[Image:Na-lamp-3.jpg|200px|left]]
 
  
Sodium in its metallic form can be used to refine some reactive metals, such as [[zirconium]] and [[potassium]], from their compounds. This alkali metal is also a component of [[sodium chloride]] (NaCl) which is vital to [[life]]. Other uses:
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Sodium hydroxide slowly reacts with glass to form [[sodium silicate]], so glass joints and stopcocks exposed to NaOH have a tendency to "freeze." Laboratory flasks and glass-lined [[chemical reactor]]s are damaged by long exposure to hot sodium hydroxide, and the glass becomes frosted. Sodium hydroxide does not attack [[iron]] or [[copper]], but many other metals&mdash;such as [[aluminum]], [[zinc]], and [[titanium]]&mdash;are attacked rapidly. For this reason, aluminum pans should never be cleaned with lye.
*In certain [[alloy]]s to improve their structure.
 
*In [[soap]], in combination with [[fatty acid]]s.
 
*To descale metal (make its surface smooth).
 
*To purify molten metals.
 
*In [[sodium vapor lamp]]s, an efficient means of producing light from electricity see the picture left.
 
*As a [[heat transfer fluid]] in some types of [[nuclear reactors]] and inside the hollow [[valve]]s of high-performance [[internal combustion engine]]s.
 
  
[[NaCl]], a compound of sodium ions and [[chloride]] ions, is an important [[heat transfer]] material.
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Unlike NaOH, the hydroxides of most metals are insoluble, and therefore sodium hydroxide can be used to precipitate metal hydroxides. One such hydroxide is [[aluminum hydroxide]], used as a gelatinous [[flocculation|floc]] to filter out particulate matter in [[water treatment]].
  
[[Image:Starfield Optical Range - sodium laser.jpg|thumb|right|300px|A dye laser used at the Starfire Optical Range for LIDAR and laser guide star experiments is tuned to the sodium D line and used to excite sodium atoms in the upper atmosphere.]]
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== Applications ==
  
== Compounds ==
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Sodium, its alloys, ions, and compounds have a wide range of applications. Some of them are listed below.
[[Sodium chloride]] or [[halite]], better known as common salt, is the most common compound of sodium, but sodium occurs in many other [[mineral]]s, such as [[amphibole]], [[cryolite]], [[soda niter]] and [[zeolite]]. 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.
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*The metallic form of sodium can be used to isolate some metals, such as [[zirconium]] and [[potassium]], from their compounds.
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*Sodium metal is used to manufacture several compounds, including sodium cyanide, sodium hydride, and sodium peroxide.
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*Sodium is used to descale (smoothen) metal surfaces and to purify molten metals.
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*Sodium vapor lamps provide an efficient means of producing light from electricity.
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*Sodium is added to certain [[alloy]]s to improve their structure.
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*An alloy of sodium and [[potassium]] (NaK) is a heat-transfer medium and a chemical reducing agent.
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*Soap is generally a sodium salt of certain fatty acids.
  
The sodium compounds that are the most important to industry are common salt (Na[[chlorine|Cl]]), [[soda ash]] (Na<sub>2</sub>[[carbon|C]][[oxygen|O]]<sub>3</sub>), [[baking soda]] (Na[[hydrogen|H]]CO<sub>3</sub>), [[sodium hydroxide|caustic soda]] (NaOH), [[sodium nitrate|Chile saltpeter]] (Na[[nitrogen|N]]O<sub>3</sub>), di- and tri-sodium phosphates, [[sodium thiosulfate]] (hypo, Na<sub>2</sub>[[sulfur|S]]<sub>2</sub>O<sub>3</sub> · 5H<sub>2</sub>O), and [[borax]] (Na<sub>2</sub>[[boron|B]]<sub>4</sub>O<sub>7</sub> · 10H<sub>2</sub>O).
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[[Image:Starfield Optical Range - sodium laser.jpg|thumb|right|300px|A dye laser used at the Starfire Optical Range for LIDAR and laser guide star experiments is tuned to the sodium D line and used to excite sodium atoms in the upper atmosphere]]
  
''See also [[:category:Sodium compounds|sodium compounds]].''
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*Sodium bicarbonate is used as an antacid to treat acid indigestion and as an ingredient in some types of toothpaste. In combination with acidic materials (such as lemon juice), it acts as a leavening agent in baking. It is commonly used to increase the alkalinity of water in pools and spas, especially when the chlorine content is high.
  
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*Sodium carbonate is used in the manufacture of [[glass]], [[paper]], [[detergent]]s, and chemicals such as sodium silicates and phosphates. Many chemical industries use it as an [[alkaline]] agent. It is widely used in processing photographic film, when alkaline conditions are needed for the action of [[Photographic developer|developing agents]]. Domestically, it is used as a water softener for laundry, as it prevents [[magnesium]] and [[calcium]] ions in hard water from bonding to the detergent.
  
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*Sodium chloride is widely used as a flavor enhancer in foods. It is also used in [[manufacturing]] pulp and paper, setting dyes in textiles, and producing [[soap]]s and [[detergent]]s. In much of North America, large quantities of rock salt are used to help clear highways of ice during winter. In addition, sodium chloride is the raw material used to produce [[chlorine]], which in turn is used for the production of many modern materials including [[polyvinyl chloride]] and [[pesticide]]s.
  
== Precautions ==
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* Sodium hydroxide is used in industry mostly as a strong [[chemical compound|chemical]] [[pH|base]] in the manufacture of pulp and [[paper]], [[textile]]s, [[soap]]s, and [[detergent]]s. It is used to drive chemical reactions and to measure the concentrations of acids. Food uses of lye include washing or chemical peeling of [[fruit]]s and [[vegetable]]s, [[chocolate]] and [[cocoa]] processing, [[caramel]] color production, [[poultry]] scalding, [[soft drink]] processing, and [[ice cream]] thickening. [[Olive]]s are often soaked in lye to soften them, while [[pretzel]]s and [[Germany|German]] [[lye roll]]s are glazed with a lye solution before baking to make them crisp. Sodium hydroxide is used in the home as an agent for unclogging blocked drains.
Sodium's metallic form is highly explosive in water and is a poison when uncombined with other elements. The powdered form may combust spontaneously in air or oxygen. This metal should be handled carefully at all times. Sodium must be stored either in an inert [[Earth's atmosphere|atmosphere]], or under a liquid hydrocarbon such as mineral oil or [[kerosene]].
 
  
 
==Physiology and sodium ions==
 
==Physiology and sodium ions==
Sodium ions play a diverse and important 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]].
 
  
Some potent [[neurotoxin]]s, such as [[batrachotoxin]], increase the sodium ion permeability of the [[cell membrane]]s in nerves and muscles, causing a massive and irreversible [[depolarization]] of the membranes, with potentially fatal consequences.
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Sodium ions play important roles in a variety of physiological processes. For example, sodium ions are necessary for the regulation of blood and body fluids, transmission of nerve impulses, heart activity, and various metabolic functions.
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Unfortunately, many people ingest sodium chloride (table salt) in excess, which can have negative effects on health. It can lead to elevated levels of [[blood pressure]], which in turn is associated with increased risks of [[heart attack]] and [[stroke]]. Excessive salt consumption can also dehydrate the human body.
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Many [[microorganism]]s cannot live in an overly salty environment, as water is drawn out of their cells by [[osmosis]]. For this reason, salt is used to preserve some foods, such as smoked bacon or fish. It has also been used to disinfect wounds.
  
 
==References==
 
==References==
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* [[Periodic table]]
 
* [[Periodic table]]
* [[:Category:Sodium compounds]]
 
* [[:Category:Alkali metals]]
 
  
 
==External links==
 
==External links==
 
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All links retrieved January 30, 2023.
 
*[http://www.webelements.com/webelements/elements/text/Na/index.html WebElements.com – Sodium]
 
*[http://www.webelements.com/webelements/elements/text/Na/index.html WebElements.com – Sodium]
*[http://www.theodoregray.com/PeriodicTable/Elements/011/index.html The Wooden Periodic Table Table's Entry on Sodium]
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*[http://www.theodoregray.com/PeriodicTable/Elements/011/index.html The Wooden Periodic Table Table Entry on Sodium]
 
*[http://www.americanheart.org/presenter.jhtml?identifier=4708 Dietary Sodium]
 
*[http://www.americanheart.org/presenter.jhtml?identifier=4708 Dietary Sodium]
  
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[[Category:Chemistry]]
 
[[Category:Chemistry]]
  
{{credit|69271585}}
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{{credit5|Sodium|69271585|Sodium_bicarbonate|69387229|Sodium_carbonate|69193552|Sodium_chloride|67824084|Sodium_hydroxide|69339562}}

Latest revision as of 21:54, 30 January 2023

11 neonsodiummagnesium
Li

Na

K
Na-TableImage.png
periodic table
General
Name, Symbol, Number sodium, Na, 11
Chemical series alkali metals
Group, Period, Block 1, 3, s
Appearance silvery white
Na,11.jpg
Atomic mass 22.98976928(2) g/mol
Electron configuration [Ne] 3s1
Electrons per shell 2, 8, 1
Physical properties
Phase solid
Density (near r.t.) 0.968 g/cm³
Liquid density at m.p. 0.927 g/cm³
Melting point 370.87 K
(97.72 °C, 207.9 °F)
Boiling point 1156 K
(883 °C, 1621 °F)
Critical point (extrapolated)
2573 K, 35 MPa
Heat of fusion 2.60 kJ/mol
Heat of vaporization 97.42 kJ/mol
Heat capacity (25 °C) 28.230 J/(mol·K)
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 554 617 697 802 946 1153
Atomic properties
Crystal structure cubic body centered
Oxidation states 1
(strongly basic oxide)
Electronegativity 0.93 (Pauling scale)
Ionization energies
(more)
1st: 495.8 kJ/mol
2nd: 4562 kJ/mol
3rd: 6910.3 kJ/mol
Atomic radius 180 pm
Atomic radius (calc.) 190 pm
Covalent radius 154 pm
Van der Waals radius 227 pm
Miscellaneous
Magnetic ordering paramagnetic
Electrical resistivity (20 °C) 47.7 nΩ·m
Thermal conductivity (300 K) 142 W/(m·K)
Thermal expansion (25 °C) 71 µm/(m·K)
Speed of sound (thin rod) (20 °C) 3200 m/s
Speed of sound (thin rod) (r.t.) 10 m/s
Shear modulus 3.3 GPa
Bulk modulus 6.3 GPa
Mohs hardness 0.5
Brinell hardness 0.69 MPa
CAS registry number 7440-23-5
Notable isotopes
Main article: Isotopes of sodium
iso NA half-life DM DE (MeV) DP
22Na syn 2.602 y β+ 0.546 22Ne
ε - 22Ne
γ 1.2745 -
23Na 100% Na is stable with 12 neutrons

Sodium (chemical symbol Na, atomic number 11) is a member of a group of chemical elements known as alkali metals. Silvery in color, it is soft, waxy, and lightweight. It is highly reactive, oxidizing rapidly in air and reacting violently with water to produce the alkali sodium hydroxide and hydrogen gas. Given its reactivity, sodium is not found as a free metal in nature but is bound to other elements in the form of compounds. It also occurs as cations in seawater.

Sodium metal can be used to isolate some other metals from their compounds, smoothen metal surfaces, and manufacture several compounds. Sodium vapor lamps provide bright illumination at low cost. An alloy of sodium and potassium (NaK) is a heat-transfer medium and a chemical reducing agent.

Moreover, the compounds of sodium have numerous applications. Common salt, or table salt, is sodium chloride, widely used as a food flavoring. It provides the body with sodium ions, which are essential nutrients, but excessive amounts are harmful for health. It is also an agent for de-icing highways in the winter. Sodium bicarbonate is an antacid, a leavening agent in baking, and an ingredient in some forms of toothpaste. Sodium hydroxide is a powerful chemical base, but sodium bicarbonate and sodium carbonate are also used to raise the alkalinity of solutions. The carbonate, chloride, and hydroxide of sodium are important industrial chemicals, used in the manufacture of glass, pulp and paper, textiles, soaps and detergents, and other sodium salts.

Isolation and etymology

Compounds of sodium have long been known. The metal itself was first isolated in 1807, when Sir Humphry Davy carried out the electrolysis of caustic soda (sodium hydroxide). Sodium was deposited on the cathode.

The name sodium comes from the English word, soda. The symbol for sodium, Na, comes from the neo-Latin name for a common sodium compound called natrium. That name in turn comes from the Greek nítron, a kind of natural salt. In medieval Europe, a compound of sodium with the Latin name sodanum was used as a headache remedy.

Occurrence and production

Sodium is the most abundant alkali metal and makes up about 2.6 percent by weight of the Earth's crust. Naturally occurring sodium is bound to other elements in many minerals. The most common sodium-containing mineral is halite (or rock salt), chemically known as sodium chloride. Other minerals that contain sodium include cryolite (sodium aluminum fluoride), soda ash (sodium carbonate), and soda niter (or Chile saltpeter, sodium nitrate), as well as several members of the amphibole and zeolite groups of minerals.

Sodium is relatively abundant in stars. Its spectral lines, known as the sodium D lines, are among the most prominent in starlight.

At the end of the nineteenth century, sodium was chemically prepared by heating sodium carbonate with carbon to 1,100 °C. The reaction may be written as follows.

Na2CO3 (liquid) + 2 C (solid, coke) → 2 Na (vapor) + 3 CO (gas).

Sodium is now produced commercially through the electrolysis of fused (liquefied) sodium chloride. In this process, known as the Downs process, calcium chloride is mixed with the sodium chloride to lower the melting point below 600 °C. Sodium, but not calcium, is deposited on the cathode. This method is less expensive than the earlier method of electrolyzing sodium hydroxide.

Notable characteristics

The flame test for sodium displays a brilliantly bright yellow emission due to the so-called "sodium D lines" at 588.9950 and 589.5924 nanometers.

As an alkali metal, sodium lies in group 1 (former group 1A) of the periodic table, between lithium and potassium. In addition, it is at the beginning of period 3, situated just before magnesium.

Like the other alkali metals, sodium metal is a soft, lightweight, reactive metal. Owing to its extreme reactivity, its occurrence in nature takes the form of compounds, never as the pure element. Sodium metal floats on water and reacts violently with it, releasing heat, hydrogen gas, and caustic sodium hydroxide solution. When sodium or its compounds are burned in a flame, they give off a distinct yellow color, corresponding to two main spectral lines—the "sodium D lines" at wavelengths 588.9950 and 589.5924 nanometers.

In 1860, in their paper "Chemical Analysis by Observation of Spectra" in the scientific journal Annalen der Physik und der Chemie, Gustav Kirchhoff and Robert Bunsen reported: "In a corner of our 60 cu.m. (cubic meter) room farthest away from the apparatus, we exploded 3 mg. (milligrams) of sodium chlorate with milk sugar, while observing the nonluminous flame before the slit. After a few minutes, the flame gradually turned yellow and showed a strong sodium line that disappeared only after 10 minutes. From the weight of the sodium salt and the volume of air in the room, we easily calculate that one part by weight of air could not contain more than 1/20 millionth weight of sodium."

Under extreme pressure, sodium departs from standard rules for changing to a liquid state. Most materials need more thermal energy to melt under high pressure than they do at normal atmospheric pressure. This is because the molecules are packed closer together and have less room to move. At a pressure of 30 gigapascals (300,000 times sea-level atmospheric pressure), the melting temperature of sodium begins to drop. At around 100 gigapascals, sodium melts near room temperature.

A possible explanation for the aberrant behavior of sodium is that this element has one unpaired electron (in the outermost shell) that is pushed closer to the other ten electrons when placed under pressure, forcing interactions that are normally absent. While under pressure, solid sodium assumes several odd crystal structures, suggesting that the liquid might have unusual properties such as superconductivity or superfluidity (Gregoryanz et al. 2005).

Isotopes

There are 13 known isotopes of sodium, of which the only stable one is 23Na. Sodium has two radioactive cosmogenic isotopes—that is, isotopes produced when high-energy cosmic rays interact with the nuclei of sodium atoms. They are 22Na, with a half-life of 2.605 years, and 24Na, with a half-life of about 15 hours.

Exposure to high levels of neutron radiation (such as from a nuclear reactor accident) converts some of the stable 23Na in human blood plasma to 24Na. By measuring the concentration of the latter isotope, the neutron radiation dosage to the victim can be computed.

Precautions

Sodium metal should be handled carefully at all times. It is highly explosive in water and is a poison when uncombined with other elements. The powdered form may burn spontaneously in air or oxygen. For these reasons, sodium must be stored either in an inert atmosphere or under a liquid hydrocarbon such as mineral oil or kerosene.

Compounds

Sodium bicarbonate

Sodium bicarbonate (NaHCO3) is also known as sodium hydrogen carbonate, or bicarbonate of soda, or baking soda. It is a soluble white compound, with a slight alkaline taste resembling that of sodium carbonate. It is found in many mineral springs and also produced artificially.

When exposed to an acid, sodium bicarbonate releases carbon dioxide and water. The reaction is as follows.

NaHCO3 + HCl Å® NaCl + H2O + CO2 (gas)
NaHCO3 + CH3COOH Å® NaCH3COO + H2O + CO2 (gas)

Above 60°C, sodium bicarbonate gradually decomposes into sodium carbonate, water, and carbon dioxide, and at 200°C it is completely decomposed into sodium carbonate:

2NaHCO3 Å® Na2CO3 + H2O + CO2

Sodium carbonate

Sodium carbonate (Na2CO3), also known as washing soda or soda ash, is a sodium salt of carbonic acid (H2CO3). It most commonly occurs as a crystalline heptahydrate (Na2CO3.7H2O) that readily loses water from the crystals to form a white powder, the monohydrate (Na2CO3.H2O). It has a cooling, alkaline taste and can be extracted from the ashes of many plants. It is produced artificially in large quantities from common salt (sodium chloride).

Although sodium carbonate is soluble in water, it can occur naturally in arid regions, especially in the mineral deposits (evaporites) formed when seasonal lakes evaporate. Deposits of the mineral natron, a combination of sodium carbonate and sodium bicarbonate, have been mined from dry lake bottoms in Egypt since ancient times, when natron was used in the preparation of mummies and in the early manufacture of glass.

Sodium chloride

Sodium chloride, also known as common salt or table salt, is a compound with the chemical formula NaCl. It is found in large quantities in seawater and as the mineral halite or rock salt. It is the salt most responsible for the salinity of the oceans. It is produced by the evaporation of seawater, brine wells, and salt lakes, and by mining rock salt.

This salt is essential to life on Earth. It is present (at various concentrations) in most biological tissues and body fluids. The concentration of sodium ions in the blood is directly related to the regulation of safe body-fluid levels. The propagation of nerve impulses (by "signal transduction") is regulated by sodium ions. Humans are unusual among primates in secreting large amounts of salt by sweating. On the other hand, too much salt in the body is bad for health.

As the main ingredient in edible salt, sodium chloride is commonly used as a condiment and food preservative. Its usefulness as a food preservative helped eliminate human dependency on the seasonal availability of food and allowed travel over long distances. By the Middle Ages, caravans consisting of as many as 40,000 camels traversed four hundred miles of the Sahara bearing salt, sometimes trading it for slaves.

There are many references to common salt in the Bible. A familiar story is about Lot's wife, who was turned into a pillar of salt when she disobeyed the angels and looked back at the wicked city of Sodom (Genesis 19:26). In the Sermon on the Mount, Jesus told his followers that they were the "salt of the earth," referring to their internal, spiritual flavoring that they needed to distribute to others. Furthermore, in several religious traditions, common salt is used to bless (or spiritually purify) people, places, and things. This usage is probably based on the clean appearance of pure salt, its chemical stability, and its value for living things.

Sodium hydroxide

Sodium hydroxide (NaOH), also known as lye or caustic soda, is a strong chemical base, widely used in chemical laboratories and in industry. The pure substance is a white solid, available in pellets, flakes, and granules, and also as a 50 percent saturated solution. It readily absorbs water and carbon dioxide from the air, so it should be stored in an airtight container.

This substance is very soluble in water, and the process of dissolving it liberates heat. It also dissolves in other polar solvents such as ethanol and methanol, but it is insoluble in nonpolar solvents such as diethyl ether.

Gloves and eye protection should be worn when using sodium hydroxide, because it can cause chemical burns, injury or scarring, and blindness. An apron of polyvinyl chloride is also recommended when concentrated solutions or the solid form are used. It should be stored well away from strong acids such as sulfuric acid.

Caustic soda is produced by the electrolysis of an aqueous solution of sodium chloride. It builds up at the cathode, where water is reduced to hydrogen gas and hydroxide ions. The process, called the "chloralkali process," also produces chlorine.

Sodium hydroxide is an ionic compound, made up of sodium ions and hydroxide ions. The hydroxide ion makes sodium hydroxide a strong base, which reacts with acids to form water and the corresponding salts. For example, with hydrochloric acid, sodium chloride is formed:

NaOH(aq) + HCl(aq) Å® NaCl(aq) + H2O(l)

Such acid-base reactions can also be used for titrations, and this is a common way for measuring the concentration of acids. Related to this is the reaction of sodium hydroxide with acidic oxides such as carbon dioxide (CO2) and sulfur dioxide (SO2). Such reactions are often used to "scrub" harmful acidic gases (like SO2 and H2S) and prevent their release into the atmosphere.

Sodium hydroxide slowly reacts with glass to form sodium silicate, so glass joints and stopcocks exposed to NaOH have a tendency to "freeze." Laboratory flasks and glass-lined chemical reactors are damaged by long exposure to hot sodium hydroxide, and the glass becomes frosted. Sodium hydroxide does not attack iron or copper, but many other metals—such as aluminum, zinc, and titanium—are attacked rapidly. For this reason, aluminum pans should never be cleaned with lye.

Unlike NaOH, the hydroxides of most metals are insoluble, and therefore sodium hydroxide can be used to precipitate metal hydroxides. One such hydroxide is aluminum hydroxide, used as a gelatinous floc to filter out particulate matter in water treatment.

Applications

Sodium, its alloys, ions, and compounds have a wide range of applications. Some of them are listed below.

  • The metallic form of sodium can be used to isolate some metals, such as zirconium and potassium, from their compounds.
  • Sodium metal is used to manufacture several compounds, including sodium cyanide, sodium hydride, and sodium peroxide.
  • Sodium is used to descale (smoothen) metal surfaces and to purify molten metals.
  • Sodium vapor lamps provide an efficient means of producing light from electricity.
  • Sodium is added to certain alloys to improve their structure.
  • An alloy of sodium and potassium (NaK) is a heat-transfer medium and a chemical reducing agent.
  • Soap is generally a sodium salt of certain fatty acids.
A dye laser used at the Starfire Optical Range for LIDAR and laser guide star experiments is tuned to the sodium D line and used to excite sodium atoms in the upper atmosphere
  • Sodium bicarbonate is used as an antacid to treat acid indigestion and as an ingredient in some types of toothpaste. In combination with acidic materials (such as lemon juice), it acts as a leavening agent in baking. It is commonly used to increase the alkalinity of water in pools and spas, especially when the chlorine content is high.
  • Sodium carbonate is used in the manufacture of glass, paper, detergents, and chemicals such as sodium silicates and phosphates. Many chemical industries use it as an alkaline agent. It is widely used in processing photographic film, when alkaline conditions are needed for the action of developing agents. Domestically, it is used as a water softener for laundry, as it prevents magnesium and calcium ions in hard water from bonding to the detergent.
  • Sodium chloride is widely used as a flavor enhancer in foods. It is also used in manufacturing pulp and paper, setting dyes in textiles, and producing soaps and detergents. In much of North America, large quantities of rock salt are used to help clear highways of ice during winter. In addition, sodium chloride is the raw material used to produce chlorine, which in turn is used for the production of many modern materials including polyvinyl chloride and pesticides.
  • Sodium hydroxide is used in industry mostly as a strong chemical base in the manufacture of pulp and paper, textiles, soaps, and detergents. It is used to drive chemical reactions and to measure the concentrations of acids. Food uses of lye include washing or chemical peeling of fruits and vegetables, chocolate and cocoa processing, caramel color production, poultry scalding, soft drink processing, and ice cream thickening. Olives are often soaked in lye to soften them, while pretzels and German lye rolls are glazed with a lye solution before baking to make them crisp. Sodium hydroxide is used in the home as an agent for unclogging blocked drains.

Physiology and sodium ions

Sodium ions play important roles in a variety of physiological processes. For example, sodium ions are necessary for the regulation of blood and body fluids, transmission of nerve impulses, heart activity, and various metabolic functions.

Unfortunately, many people ingest sodium chloride (table salt) in excess, which can have negative effects on health. It can lead to elevated levels of blood pressure, which in turn is associated with increased risks of heart attack and stroke. Excessive salt consumption can also dehydrate the human body.

Many microorganisms cannot live in an overly salty environment, as water is drawn out of their cells by osmosis. For this reason, salt is used to preserve some foods, such as smoked bacon or fish. It has also been used to disinfect wounds.

References
ISBN links support NWE through referral fees

  • Los Alamos National Laboratory – Sodium
  • Gregoryanz, E., et al. (2005). Melting of dense sodium. Physical Review Letters: in press.
  • Rebecca J. Donatelle. Health, The Basics. 6th ed. San Francisco: Pearson Education, Inc. 2005.

See also

External links

All links retrieved January 30, 2023.

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