Editing Sodium (section)

==Chemistry==
{{Main|Sodium compounds}}
Sodium atoms have 11 electrons, one more than the stable configuration of the [[noble gas]] [[neon]]. The first and second [[ionization energies]] are 495.8&nbsp;kJ/mol and 4562&nbsp;kJ/mol, respectively. As a result, sodium usually forms [[ionic compound]]s involving the Na<sup>+</sup> cation.<ref>{{cite book|title=Cambridge International AS and A Level Chemistry Coursebook|author=Lawrie Ryan|author2= Roger Norris|publisher=Cambridge University Press, 2014|edition=illustrated|isbn=978-1-107-63845-7|page=36|date=31 July 2014}}</ref>

===Metallic sodium===
Metallic sodium is generally less reactive than [[potassium]] and more reactive than [[lithium]].<ref>{{cite web|last=De Leon|first=N.|title=Reactivity of Alkali Metals|url=http://www.iun.edu/~cpanhd/C101webnotes/modern-atomic-theory/alkali-reac.html|publisher=[[Indiana University Northwest]]|access-date=7 December 2007|archive-date=16 October 2018|archive-url=https://web.archive.org/web/20181016113143/http://www.iun.edu/~cpanhd/C101webnotes/modern-atomic-theory/alkali-reac.html|url-status=dead}}</ref> Sodium metal is highly reducing, with the [[standard reduction potential]] for the Na<sup>+</sup>/Na couple being −2.71 volts,<ref>{{cite book|last1=Atkins|first1=Peter W.|last2=de Paula|first2=Julio|title=Physical Chemistry|date=2002|edition=7th|publisher=W. H. Freeman|isbn=978-0-7167-3539-7|oclc=3345182|url=https://archive.org/details/physicalchemistr0000atki}}</ref> though potassium and lithium have even more negative potentials.<ref>{{cite book|last=Davies|first=Julian A.|title=Synthetic Coordination Chemistry: Principles and Practice|date=1996|publisher=World Scientific|isbn=978-981-02-2084-6|oclc=717012347|page=293}}</ref>

===Salts and oxides===
{{Category see also|Sodium compounds}}
[[File:NaCl polyhedra.png|thumb|The structure of [[sodium chloride]], showing octahedral coordination around Na<sup>+</sup> and Cl<sup>−</sup> centres. This framework disintegrates when dissolved in water and reassembles when the water evaporates.]]
Sodium compounds are of immense commercial importance, being particularly central to industries producing [[glass]], [[paper]], [[soap]], and [[textile]]s.{{Sfn|Greenwood|Earnshaw|1997|p=89}} The most important sodium compounds are [[table salt]] (Na[[chloride|Cl]]), [[soda ash]] (Na<sub>2</sub>[[carbonate|CO<sub>3</sub>]]), [[baking soda]] (Na[[Bicarbonate|HCO<sub>3</sub>]]), [[sodium hydroxide|caustic soda]] (NaOH), [[sodium nitrate]] (Na[[nitrate|NO<sub>3</sub>]]), di- and tri-[[sodium phosphates]], [[sodium thiosulfate]] (Na<sub>2</sub>[[thiosulfate|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).<ref name="Holl" /> In compounds, sodium is usually [[ionic bond|ionically bonded]] to water and anions and is viewed as a [[HSAB|hard]] [[Lewis acid]].<ref>{{cite book|last=Cowan|first=James A.|title=Inorganic Biochemistry: An Introduction|date=1997|publisher=Wiley-VCH|isbn=978-0-471-18895-7|page=7|oclc=34515430}}</ref>

[[File:Sodium stearate v2.svg|thumb|center|upright=1.4|Two equivalent images of the chemical structure of [[sodium stearate]], a typical soap]]
Most [[soap]]s are sodium salts of [[fatty acid]]s. Sodium soaps have a higher melting temperature (and seem "harder") than potassium soaps.<ref name="Holl">{{cite book|publisher=Walter de Gruyter|date=1985|edition=91–100|pages=931–943|isbn=978-3-11-007511-3|title=Lehrbuch der Anorganischen Chemie|last1=Holleman|first1=Arnold F.|last2=Wiberg|first2=Egon|last3=Wiberg|first3=Nils|language=de}}</ref>

Like all the [[alkali metal]]s, sodium reacts [[Exothermic reaction|exothermically]] with water. The reaction produces caustic soda ([[sodium hydroxide]]) and flammable [[hydrogen]] gas. When burned in air, it forms primarily [[sodium peroxide]] with some [[sodium oxide]].{{sfn|Greenwood|Earnshaw|1997|p=84}}

===Aqueous solutions===
Sodium tends to form water-soluble compounds, such as [[halides]], [[sulfate]]s, [[nitrates]], [[carboxylates]] and [[carbonate]]s. The main aqueous species are the aquo complexes [Na(H<sub>2</sub>O)<sub>''n''</sub>]<sup>+</sup>, where ''n'' = 4–8; with ''n'' = 6 indicated from X-ray diffraction data and computer simulations.<ref name="Lincoln">{{cite book|doi=10.1016/B0-08-043748-6/01055-0|title=Comprehensive Coordination Chemistry II|date=2004|isbn=978-0-08-043748-4|page=515|chapter=Metal Aqua Ions|last1=Lincoln|first1=S. F.|last2=Richens|first2=D. T.|last3=Sykes|first3=A. G.}}</ref>

Direct precipitation of sodium salts from aqueous solutions is rare because sodium salts typically have a high affinity for water. An exception is [[sodium bismuthate]] (NaBiO<sub>3</sub>),<ref>{{cite book|title=Lange's Handbook of Chemistry|publisher=McGraw-Hill|date=1998|isbn=978-0-07-016384-3|last1=Dean|first1=John Aurie|last2=Lange|first2=Norbert Adolph}}</ref> which is insoluble in cold water and decomposes in hot water.<ref name="me">{{Cite book|title=The Merck index|date=2000|publisher=Chapman & Hall Electronic Pub. Division|isbn=978-1-58488-129-2|edition=12th|pages=1357}}</ref> Because of the high solubility of its compounds, sodium salts are usually isolated as solids by evaporation or by precipitation with an organic antisolvent, such as [[ethanol]]; for example, only 0.35&nbsp;g/L of sodium chloride will dissolve in ethanol.<ref>{{cite book|last=Burgess|first= J.|title=Metal Ions in Solution|publisher=Ellis Horwood|location=New York|date=1978|isbn=978-0-85312-027-8}}</ref> A [[crown ether]] such as [[15-crown-5]] may be used as a [[phase-transfer catalyst]].<ref>{{cite book|last1=Starks|first1=Charles M.|last2=Liotta|first2=Charles L.|last3=Halpern|first3=Marc|title=Phase-Transfer Catalysis: Fundamentals, Applications, and Industrial Perspectives|date=1994|publisher=Chapman & Hall|page=162|isbn=978-0-412-04071-9|oclc=28027599}}</ref>

Sodium content of samples is determined by [[atomic absorption spectrophotometry]] or by [[potentiometry]] using ion-selective electrodes.<ref>{{cite journal|last=Levy|first=G. B.|title=Determination of Sodium with Ion-Selective Electrodes|journal=Clinical Chemistry|url=http://www.clinchem.org/content/27/8/1435|volume=27|issue=8|pages=1435–1438|date=1981|doi=10.1093/clinchem/27.8.1435|pmid=7273405|access-date=26 November 2011|archive-date=5 February 2016|archive-url=https://web.archive.org/web/20160205222850/http://www.clinchem.org/content/27/8/1435|url-status=live|doi-access=free}}</ref>

===Electrides and sodides===
Like the other alkali metals, sodium dissolves in ammonia and some amines to give deeply colored solutions; evaporation of these solutions leaves a shiny film of metallic sodium. The solutions contain the [[coordination complex]] [Na(NH<sub>3</sub>)<sub>6</sub>]<sup>+</sup>, with the positive charge counterbalanced by [[electride|electrons as anions]]; [[cryptand]]s permit the isolation of these complexes as crystalline solids. Sodium forms complexes with crown ethers, cryptands and other ligands.<ref>{{cite book|title=Applications of the Newer Techniques of Analysis|date=6 December 2012|editor=Ivor L. Simmons|publisher=Springer Science & Business Media, 2012|isbn=978-1-4684-3318-0|page=160}}</ref>

For example, [[15-crown-5]] has a high affinity for sodium because the cavity size of 15-crown-5 is 1.7–2.2&nbsp;Å, which is enough to fit the sodium ion (1.9&nbsp;Å).<ref>{{cite book|title=Design, Fabrication, Properties and Applications of Smart and Advanced Materials|editor=Xu Hou|publisher=CRC Press, 2016|edition=illustrated|isbn=978-1-4987-2249-0|page=175|date=22 June 2016}}</ref><ref>{{cite book|title=Anionic Polymerization: Principles, Practice, Strength, Consequences and Applications|editor=Nikos Hadjichristidis|editor2=Akira Hirao|publisher=Springer|edition=illustrated|isbn=978-4-431-54186-8|page=349|date=2015}}</ref> Cryptands, like crown ethers and other [[ionophore]]s, also have a high affinity for the sodium ion; derivatives of the [[alkalide]] Na<sup>−</sup> are obtainable<ref>{{cite journal|journal=[[J. Am. Chem. Soc.]]|last1=Dye|first1=J. L.|last2=Ceraso|first2=J. M.|author3=Mei Lok Tak|last4=Barnett|first4=B. L.|last5=Tehan|first5=F. J.|title=Crystalline Salt of the Sodium Anion (Na<sup>−</sup>)|date=1974|volume=96|issue=2|pages=608–609|doi=10.1021/ja00809a060|bibcode=1974JAChS..96..608D }}</ref> by the addition of cryptands to solutions of sodium in ammonia via [[disproportionation]].<ref>{{cite book|last1=Holleman|first1=A. F.|last2=Wiberg|first2=E.|last3=Wiberg|first3=N.|title=Inorganic Chemistry|publisher=Academic Press|date=2001|isbn=978-0-12-352651-9|oclc=48056955}}</ref>

===Organosodium compounds===
{{Main|Organosodium chemistry}}
[[File:Monensin2.png|thumb|The structure of the complex of sodium (Na<sup>+</sup>, shown in yellow) and the antibiotic [[monensin]]-A]]
Many organosodium compounds have been prepared. Because of the high polarity of the C-Na bonds, they behave like sources of [[carbanion]]s (salts with organic [[anion]]s). Some well-known derivatives include [[sodium cyclopentadienide]] (NaC<sub>5</sub>H<sub>5</sub>) and [[trityl]] sodium ((C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>CNa).<ref>{{OrgSynth | first1=W. B.  Jr. | last1=Renfrow |first2=C. R. | last2= Hauser |year=1943 |title=Triphenylmethylsodium |collvol=2 |collvolpages=607 |prep=CV2P0607}}</ref> [[Sodium naphthalene]], Na<sup>+</sup>[C<sub>10</sub>H<sub>8</sub>•]<sup>−</sup>, a strong reducing agent, forms upon mixing Na and naphthalene in ethereal solutions.{{sfn|Greenwood|Earnshaw|1997|p=111}}

===Intermetallic compounds===
Sodium forms alloys with many metals, such as potassium, [[calcium]], [[lead]], and the [[group 11 element|group 11]] and [[group 12 elements|12]] elements. Sodium and potassium form KNa<sub>2</sub> and [[NaK]]. NaK is 40–90% potassium and it is liquid at [[ambient temperature]]. It is an excellent thermal and electrical conductor. Sodium-calcium alloys are by-products of the electrolytic production of sodium from a binary salt mixture of NaCl-CaCl<sub>2</sub> and ternary mixture NaCl-CaCl<sub>2</sub>-BaCl<sub>2</sub>. Calcium is only partially [[miscible]] with sodium, and the 1–2% of it dissolved in the sodium obtained from said mixtures can be precipitated by cooling to 120&nbsp;°C and filtering.<ref name="pearson1991">{{cite book |author1=Paul Ashworth |author2=Janet Chetland |editor1-last=Brian |editor1-first=Pearson |title=Speciality chemicals: Innovations in industrial synthesis and applications |date=31 December 1991 |publisher=Elsevier Applied Science |location=London |isbn=978-1-85166-646-1 |pages=259–278 |access-date=27 July 2021 |url=https://books.google.com/books?id=i0AEIrEUfg0C&pg=PA259 |edition=illustrated |archive-date=16 December 2021 |archive-url=https://web.archive.org/web/20211216161948/https://books.google.com/books?id=i0AEIrEUfg0C&pg=PA259 |url-status=live }}</ref>

In a liquid state, sodium is completely miscible with lead. There are several methods to make sodium-lead alloys. One is to melt them together and another is to deposit sodium electrolytically on molten lead cathodes. NaPb<sub>3</sub>, NaPb, Na<sub>9</sub>Pb<sub>4</sub>, Na<sub>5</sub>Pb<sub>2</sub>, and Na<sub>15</sub>Pb<sub>4</sub> are some of the known sodium-lead alloys. Sodium also forms alloys with [[gold]] (NaAu<sub>2</sub>) and [[silver]] (NaAg<sub>2</sub>). Group 12 metals ([[zinc]], [[cadmium]] and [[Mercury (element)|mercury]]) are known to make alloys with sodium. NaZn<sub>13</sub> and NaCd<sub>2</sub> are alloys of zinc and cadmium. Sodium and mercury form NaHg, NaHg<sub>4</sub>, NaHg<sub>2</sub>, Na<sub>3</sub>Hg<sub>2</sub>, and Na<sub>3</sub>Hg.<ref>{{cite book|title=Alloys: Preparation, Properties, Applications|last=Habashi|first=Fathi|publisher=John Wiley & Sons, 2008|isbn=978-3-527-61192-8|pages=278–280|date=21 November 2008}}</ref>