View source for Chemistry:Chloride

{{short description|Main anion present in sea water}}
{{Chembox
| Name = Chloride anion
| ImageFileL1 = Cl-.svg
| ImageSizeL1 = 50
| ImageFileR1 = Chloride_ion.svg
| ImageSizeR1 = 60px
| SystematicName = Chloride<ref>{{Cite web|url = https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=312|title = Chloride ion - PubChem Public Chemical Database|work = The PubChem Project|location = USA|publisher = National Center for Biotechnology Information}}</ref>
|Section1={{Chembox Identifiers
| IUPHAR_ligand = 2339
| CASNo = 16887-00-6
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII = Q32ZN48698
| UNII_Ref = {{fdacite|correct|FDA}}
| PubChem = 312
| ChemSpiderID = 306
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| KEGG = C00698
| KEGG_Ref = {{keggcite|correct|kegg}}
| ChEBI = 17996
| ChEMBL = 19429
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| Beilstein = 3587171
| Gmelin = 14910
| SMILES = [Cl-]
| StdInChI = 1S/ClH/h1H/p-1
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = VEXZGXHMUGYJMC-UHFFFAOYSA-M
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
}}
|Section2={{Chembox Properties
| Formula = {{Chem2|Cl−}}
| Cl=1 
| ConjugateAcid = [[Chemistry:Hydrogen chloride|Hydrogen chloride]]
}}
|Section3={{Chembox Thermochemistry
| Entropy = 153.36&nbsp;J·K<sup>−1</sup>·mol<sup>−1</sup><ref name=b1>{{cite book| author = Zumdahl, Steven S.|title =Chemical Principles 6th Ed.| publisher = Houghton Mifflin Company| year = 2009| isbn = 978-0-618-94690-7|page=A21}}</ref>
| DeltaHf = −167&nbsp;kJ·mol<sup>−1</sup><ref name=b1 />
}}
|Section4={{Chembox Related
| OtherAnions = {{ubl|[[Chemistry:Fluoride|Fluoride]]|[[Chemistry:Bromide|Bromide]]|[[Chemistry:Iodide|Iodide]]}}
}}
}}

The term '''chloride''' refers either to a chloride [[Physics:Ion|ion]] ({{chem2|Cl−|auto=1}}), which is a negatively charged chlorine atom, or a non-charged chlorine atom covalently bonded to the rest of the molecule by a [[Chemistry:Single bond|single bond]] ({{chem2|\sCl}}). Many inorganic chlorides are [[Chemistry:Salt|salt]]s.  Many [[Chemistry:Organic compound|organic compound]]s are chlorides. The pronunciation of the word "chloride" is {{IPAc-en|ˈ|k|l|ɔər|aɪ|d}}.<ref>{{citation|last=Wells|first=John C.|year=2008|title=Longman Pronunciation Dictionary|edition=3rd|publisher=Longman|page=143|isbn=9781405881180}}</ref>

The chloride ion is an anion (negatively charged ion) with the charge Cl<sup>−</sup>. Chloride salts such as [[Chemistry:Sodium chloride|sodium chloride]] are often soluble in water.<ref name="auto">Green, John, and Sadru Damji. "Chapter 3." ''Chemistry''. Camberwell, Vic.: IBID, 2001. Print.</ref> It is an essential [[Physics:Electrolyte|electrolyte]] located in all body fluids responsible for maintaining acid/base balance, transmitting nerve impulses and regulating liquid flow in and out of cells. Other examples of ionic chlorides are [[Chemistry:Calcium chloride|calcium chloride]] {{chem2|CaCl2}} and [[Chemistry:Ammonium chloride|ammonium chloride]] {{chem2|NH4Cl}}.

The chloride is also a neutral chlorine atom [[Chemistry:Covalent bond|covalently bonded]] by a single bond to the rest of the molecule. For example, methyl chloride {{chem2|CH3Cl}} is an organic compound with a covalent C−Cl bond in which the chlorine is not an anion. Other examples of covalent chlorides are [[Chemistry:Carbon tetrachloride|carbon tetrachloride]] {{chem2|CCl4}}, [[Chemistry:Sulfuryl chloride|sulfuryl chloride]] {{chem2|SO2Cl2}} and [[Chemistry:Monochloramine|monochloramine]] {{chem2|NH2Cl}}.

==Electronic properties==
A chloride ion (diameter 167&nbsp;[[Picometre|pm]]) is much larger than a chlorine atom (diameter 99&nbsp;pm). The chlorine atom's hold on the valence shell is weaker because the chloride anion has one more electron than it does.<ref>{{Cite web |title=Size of Atoms |url=http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch7/size.html |access-date=2022-03-03 |website=chemed.chem.purdue.edu}}</ref> The ion is colorless and diamagnetic. In aqueous solution, it is highly soluble in most cases; however, for some chloride salts, such as [[Chemistry:Silver chloride|silver chloride]], [[Chemistry:Lead(II) chloride|lead(II) chloride]], and [[Chemistry:Mercury(I) chloride|mercury(I) chloride]], they are only slightly soluble in water.<ref>{{cite book|last1=Zumdahl|first1=Steven|title=Chemical Principles|date=2013|publisher=Cengage Learning|isbn=978-1-285-13370-6|pages=109|edition=7th}}<!--|access-date=24 April 2015--></ref> In aqueous solution, chloride is bonded by the protic end of the water molecules.

==Reactions of chloride==
Chloride can be oxidized but not reduced. The first oxidation, as employed in the chlor-alkali process, is conversion to chlorine gas. Chlorine can be further oxidized to other oxides and oxyanions including [[Chemistry:Hypochlorite|hypochlorite]] (ClO<sup>−</sup>, the active ingredient in chlorine [[Chemistry:Bleach|bleach]]), [[Chemistry:Chlorine dioxide|chlorine dioxide]] (ClO<sub>2</sub>), [[Chemistry:Chlorate|chlorate]] ({{chem|ClO|3|−}}), and [[Chemistry:Perchlorate|perchlorate]] ({{chem|ClO|4|−}}).

In terms of its acid–base properties, chloride is a [[Chemistry:Weak base|weak base]] as indicated by the negative value of the p''K''<sub>a</sub> of hydrochloric acid. Chloride can be protonated by strong acids, such as sulfuric acid:
:NaCl + H<sub>2</sub>SO<sub>4</sub> → NaHSO<sub>4</sub> + HCl

Ionic chloride salts reaction with other salts to exchange anions. The presence of halide ions like chloride can be detected using [[Chemistry:Silver nitrate|silver nitrate]]. A solution containing chloride ions will produce a white [[Chemistry:Silver chloride|silver chloride]] precipitate:<ref>{{Cite web |title=Testing for halide ions - Group 0 and testing ions - GCSE Chemistry (Single Science) Revision - WJEC |url=https://www.bbc.co.uk/bitesize/guides/zm426yc/revision/2 |access-date=2022-03-03 |website=BBC Bitesize |language=en-GB}}</ref>
:Cl<sup>−</sup> + Ag<sup>+</sup> → AgCl

The concentration of chloride in an assay can be determined using a [[Chemistry:Chloridometer|chloridometer]], which detects silver ions once all chloride in the assay has precipitated via this reaction.

[[Physics:Silver chloride electrode|Chlorided silver electrodes]] are commonly used in {{Lang|la|ex vivo}} [[Biology:Electrophysiology|electrophysiology]].<ref>Molleman, Areles (2003). "Patch Clamping: An Introductory Guide to Patch Clamp Electrophysiology". Wiley & Sons. {{ISBN|978-0-471-48685-5}}.</ref>

==Other oxyanions==
Chlorine can assume [[Chemistry:Oxidation state|oxidation state]]s of −1, +1, +3, +5, or +7. Several neutral [[Chemistry:Chlorine oxide|chlorine oxide]]s are also known.

:{| class="wikitable"
|-
! Chlorine oxidation state
| −1
| +1
| +3
| +5
| +7
|-
! Name
| '''chloride'''
| [[Chemistry:Hypochlorite|hypochlorite]]
| [[Chemistry:Chlorite|chlorite]]
| [[Chemistry:Chlorate|chlorate]]
| [[Chemistry:Perchlorate|perchlorate]]
|-
! Formula
| Cl<sup>−</sup>
| ClO<sup>−</sup>
| {{chem|ClO|2|−}}
| {{chem|ClO|3|−}}
| {{chem|ClO|4|−}}
|-
! Structure
| [[File:Chloride-ion-3D-vdW.png|50px|The chloride ion]]
| [[File:Hypochlorite-3D-vdW.png|50px|The hypochlorite ion]]
| [[File:Chlorite-3D-vdW.png|50px|The chlorite ion]]
| [[File:Chlorate-3D-vdW.png|50px|The chlorate ion]]
| [[File:Perchlorate-3D-vdW.png|50px|The perchlorate ion]]
|}

==Occurrence in nature==
In nature, chloride is found primarily in seawater, which has a chloride ion concentration of 19400&nbsp;mg/liter.<ref>{{Cite web|title=Chloride and Salinity|url=https://www.ldeo.columbia.edu/edu/k12/snapshotday/activities/2011/Classroom%20HS%20activity/chloride%20conversion/Chloride%20and%20Salinity.pdf|date=8 September 2011|access-date=8 January 2023|website=colombia.edu}}</ref> Smaller quantities, though at higher concentrations, occur in certain inland seas and in subterranean brine wells, such as the Great Salt Lake in Utah and the [[Earth:Dead Sea|Dead Sea]] in [[Place:Israel|Israel]].<ref>{{cite book |last1=Greenwood |first1=N. N. |title=Chemistry of the elements |date=1984 |publisher=Pergamon Press |location=Oxford [Oxfordshire] |isbn=9780750628327 |edition=1st}}</ref> 
Most chloride salts are soluble in water, thus, chloride-containing minerals are usually only found in abundance in dry climates or deep underground. Some chloride-containing minerals include [[Chemistry:Halite|halite]] (sodium chloride NaCl), [[Chemistry:Sylvite|sylvite]] (potassium chloride KCl), [[Chemistry:Bischofite|bischofite]] (MgCl<sub>2</sub>∙6H<sub>2</sub>O), [[Chemistry:Carnallite|carnallite]] (KCl∙MgCl<sub>2</sub>∙6H<sub>2</sub>O), and [[Chemistry:Kainite|kainite]] (KCl∙MgSO<sub>4</sub>∙3H<sub>2</sub>O). It is also found in evaporite minerals such as chlorapatite and [[Chemistry:Sodalite|sodalite]].

===Role in biology===
Chloride has a major physiological significance, which includes regulation of [[Biology:Osmotic pressure|osmotic pressure]], electrolyte balance and acid-base homeostasis. Chloride is present in all [[Biology:Body fluid|body fluid]]s,<ref>{{Cite journal|title=The distribution of total body chloride in man|journal=Journal of Clinical Investigation|last1=Deane|first1=Norman|volume=31|last2=Ziff|first2=Morris|issue=2|doi=10.1172/JCI102592|year=1952|at=p. 201, Table 1|language=en|pmc=436401|pmid=14907900|last3=Smith|first3=Homer W.}}</ref> and is the most abundant extracellular anion which accounts for around one third of [[Biology:Extracellular fluid|extracellular fluid]]'s [[Biology:Tonicity|tonicity]].<ref>{{cite journal |last1=Berend |first1=Kenrick |last2=van Hulsteijn |first2=Leonard Hendrik |last3=Gans |first3=Rijk O.B. |title=Chloride: The queen of electrolytes? |journal=European Journal of Internal Medicine |date=April 2012 |volume=23 |issue=3 |pages=203–211 |doi=10.1016/j.ejim.2011.11.013 |pmid=22385875}}</ref><ref>{{cite journal |last1=Rein |first1=Joshua L. |last2=Coca |first2=Steven G. |title="I don't get no respect": the role of chloride in acute kidney injury |journal=American Journal of Physiology. Renal Physiology |date=1 March 2019 |volume=316 |issue=3 |pages=F587–F605 |doi=10.1152/ajprenal.00130.2018 |pmid=30539650 |issn=1931-857X |pmc=6459301}}</ref>

Chloride is an essential [[Physics:Electrolyte#Physiological importance|electrolyte]], playing a key role in maintaining cell [[Homeostasis#Overview|homeostasis]] and transmitting action potentials in neurons.<ref>{{cite journal |title=Molecular Structure and Physiological Function of Chloride Channels |url=http://physrev.physiology.org/content/82/2/503 |journal=Physiological Reviews |date=2002-04-01 |issn=0031-9333 |pmid=11917096 |pages=503–568 |volume=82 |issue=2 |doi=10.1152/physrev.00029.2001 |first1=Thomas J. |last1=Jentsch |first2=Valentin |last2=Stein |first3=Frank |last3=Weinreich |first4=Anselm A. |last4=Zdebik}}</ref> It can flow through chloride channels (including the GABA<sub>A</sub> receptor) and is transported by KCC2 and NKCC2 transporters.

Chloride is usually (though not always) at a higher extracellular concentration, causing it to have a negative [[Biology:Reversal potential|reversal potential]] (around −61&nbsp;mV at 37&nbsp;°C in a mammalian cell).<ref>{{cite web |title=Equilibrium potentials |url=http://www.d.umn.edu/~jfitzake/Lectures/DMED/IonChannelPhysiology/MembranePotentials/EquilibriumPotentials.html |website=www.d.umn.edu}}</ref> Characteristic concentrations of chloride in model organisms are: in both ''E. coli'' and budding yeast are 10–200&nbsp;[[Physics:Molar concentration|mM]] (dependent on medium), in mammalian cells 5–100&nbsp;mM and in [[Biology:Blood plasma|blood plasma]] 100&nbsp;mM.<ref>{{cite web|url = http://book.bionumbers.org/what-are-the-concentrations-of-different-ions-in-cells/|title =Cell Biology by the Numbers: What are the concentrations of different ions in cells? |website =book.bionumbers.org|first1= Ron|last1= Milo|first2= Rob |last2=Philips|access-date=24 March 2017}}</ref>

The concentration of chloride in the blood is called [[Chemistry:Serum chloride|serum chloride]], and this concentration is regulated by the kidneys. A chloride ion is a structural component of some proteins; for example, it is present in the [[Biology:Amylase|amylase]] enzyme. For these roles, chloride is one of the essential [[Chemistry:Mineral (nutrient)|dietary mineral]] (listed by its element name ''chlorine''). [[Biology:Serum (blood)|Serum]] chloride levels are mainly regulated by the kidneys through a variety of transporters that are present along the nephron.<ref>{{cite journal |last1=Nagami |first1=Glenn T. |title=Hyperchloremia – Why and how |journal=Nefrología (English Edition) |date=1 July 2016 |volume=36 |issue=4 |pages=347–353 |doi=10.1016/j.nefro.2016.04.001 |pmid=27267918 |url=https://www.revistanefrologia.com/en-hyperchloremia-why-how-articulo-S021169951630025X |language=en |issn=2013-2514|doi-access=free }}</ref> Most of the chloride, which is filtered by the glomerulus, is reabsorbed by both proximal and distal tubules (majorly by proximal tubule) by both active and passive transport.<ref>{{cite journal |last1=Shrimanker |first1=Isha |last2=Bhattarai |first2=Sandeep |title=Electrolytes |url=https://pubmed.ncbi.nlm.nih.gov/31082167/ |website=StatPearls |publisher=StatPearls Publishing |date=2020|pmid=31082167 }}</ref>

===Corrosion===
[[Image:NaCl polyhedra.png|thumb|right|The structure of sodium chloride, revealing the tendency of chloride ions (green spheres<!--even though both spheres are equiv-->) to link to several cations.]]
The presence of chlorides, such as in seawater, significantly worsens the conditions for [[Chemistry:Pitting corrosion|pitting corrosion]] of most metals (including stainless steels, aluminum and high-alloyed materials). Chloride-induced corrosion of steel in concrete lead to a local breakdown of the protective oxide form in alkaline concrete, so that a subsequent localized corrosion attack takes place.<ref>{{cite book |last1=Criado |first1=M. |title=Handbook of Alkali-Activated Cements, Mortars and Concretes |publisher=Woodhead Publishing |isbn=978-1-78242-276-1 |pages=333–372 |chapter-url=https://www.sciencedirect.com/science/article/pii/B9781782422761500137 |language=en |chapter=13. The corrosion behaviour of reinforced steel embedded in alkali-activated mortar|date=January 2015 |doi=10.1533/9781782422884.3.333 }}</ref>

===Environmental threats===
Increased concentrations of chloride can cause a number of ecological effects in both aquatic and terrestrial environments. It may contribute to the acidification of streams, mobilize radioactive soil metals by ion exchange, affect the mortality and reproduction of aquatic plants and animals, promote the invasion of saltwater organisms into previously freshwater environments, and interfere with the natural mixing of lakes. Sodium chloride has also been shown to change the composition of microbial species at relatively low concentrations. It can also hinder the denitrification process, a microbial process essential to nitrate removal and the conservation of water quality, and inhibit the nitrification and respiration of organic matter.<ref>{{cite book |last1=Kaushal |first1=S. S. |title=Encyclopedia of Inland Waters |publisher=Academic Press |isbn=978-0-12-370626-3 |pages=23–29 |language=en |chapter=Chloride|date=19 March 2009 }}</ref>

==Production==
The chlor-alkali industry is a major consumer of the world's energy budget. This process converts sodium chloride into chlorine and sodium hydroxide, which are used to make many other materials and chemicals. The process involves two parallel reactions:
:2&nbsp;Cl<sup>−</sup> → {{chem|Cl|2}} + 2&nbsp;[[Physics:Electron|e<sup>−</sup>]]
:2&nbsp;{{chem|H|2|O}} + 2&nbsp;e<sup>−</sup> → H<sub>2</sub> + 2&nbsp;OH<sup>−</sup>
[[Image:Chloralkali membrane.svg|thumb|center|600px|Basic membrane cell used in the [[Chemistry:Electrolysis|electrolysis]] of brine. At the anode ('''A'''), chloride (Cl<sup>−</sup>) is oxidized to chlorine. The ion-selective membrane ('''B''') allows the counterion Na<sup>+</sup> to freely flow across, but prevents anions such as hydroxide (OH<sup>−</sup>) and chloride from diffusing across. At the cathode ('''C'''), water is reduced to hydroxide and hydrogen gas.]]

==Examples and uses==
An example is table salt, which is [[Chemistry:Sodium chloride|sodium chloride]] with the [[Chemistry:Chemical formula|chemical formula]] NaCl. In [[Chemistry:Water (molecule)|water]], it dissociates into Na<sup>+</sup> and Cl<sup>&minus;</sup> ions. Salts such as [[Chemistry:Calcium chloride|calcium chloride]], [[Chemistry:Magnesium chloride|magnesium chloride]], [[Chemistry:Potassium chloride|potassium chloride]] have varied uses ranging from medical treatments to cement formation.<ref name="auto"/>

Calcium chloride (CaCl<sub>2</sub>) is a salt that is marketed in [[Chemistry:Granular material|pellet]] form for removing dampness from rooms. Calcium chloride is also used for maintaining unpaved roads and for fortifying roadbases for new construction. In addition, calcium chloride is widely used as a de-icer, since it is effective in lowering the [[Physics:Melting point|melting point]] when applied to ice.<ref>{{Cite web|url=http://hyperphysics.phy-astr.gsu.edu/hbase/Chemical/saltcom.html|title=Common Salts|website=hyperphysics.phy-astr.gsu.edu|publisher=Georgia State University}}</ref>

Examples of covalently-bonded chlorides are [[Chemistry:Phosphorus trichloride|phosphorus trichloride]], [[Chemistry:Phosphorus pentachloride|phosphorus pentachloride]], and [[Chemistry:Thionyl chloride|thionyl chloride]], all three of which are reactive chlorinating [[Biology:Reagent|reagent]]s that have been used in a laboratory.

===Water quality and processing===
A major application involving chloride is [[Chemistry:Desalination|desalination]], which involves the energy intensive removal of chloride salts to give potable water. In the petroleum industry, the chlorides are a closely monitored constituent of the [[Engineering:Drilling fluid|mud system]]. An increase of the chlorides in the mud system may be an indication of drilling into a high-pressure saltwater formation. Its increase can also indicate the poor quality of a target sand.{{Citation needed|date=March 2012}}

Chloride is also a useful and reliable chemical indicator of river and groundwater fecal contamination, as chloride is a non-reactive solute and ubiquitous to sewage and potable water. Many water regulating companies around the world utilize chloride to check the contamination levels of the rivers and potable water sources.<ref>{{cite web|url=http://www.gopetsamerica.com/substance/chlorides.aspx|title=Chlorides|website=www.gopetsamerica.com|access-date=14 April 2018|archive-url=https://web.archive.org/web/20160818142707/http://www.gopetsamerica.com/substance/chlorides.aspx|archive-date=18 August 2016|url-status=dead}}</ref>

===Food===
Chloride salts such as [[Chemistry:Sodium chloride|sodium chloride]] are used to preserve food and as nutrients or condiments.

== See also ==
* [[Chemistry:Halide|Halide]] (compounds of halogens)
* Renal chloride reabsorption

== References ==
{{Reflist}}

{{Chlorides}}


[[Category:Anions]]
[[Category:Chlorides| ]]
[[Category:Dietary minerals]]

{{Sourceattribution|Chloride}}