Editing Sulfate

{{Short description|Anion of sulfur with 4 oxygen atoms}}
{{About|the inorganic ion| sulfate esters (commonly used in shampoo and personal care products)|Organosulfate}}
{{Chembox
| ImageFile1 = Sulfate-ion-2D-dimensions.svg
| ImageSize1 =170px
| ImageAlt1 = The structure and bonding of the sulfate ion. The distance between the sulfur atom and an oxygen atom is 149 picometers.
| ImageFileL1 = Sulfate-3D-vdW.png
| ImageAltL1 = [[Ball-and-stick model]] of the sulfate anion
| ImageFileR1 = Sulfate-3D-balls.png
| ImageAltR1 = 
| SystematicName = 
| IUPACName = Sulfate
| OtherNames = Tetraoxosulfate(VI)<br>Tetraoxidosulfate(VI)
|Section1={{Chembox Identifiers
| CASNo = 14808-79-8
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 7IS9N8KPMG
| EINECS = 233-334-2
| PubChem = 1117
| ChemSpiderID = 1085
| SMILES = S(=O)(=O)([O-])[O-]
| InChI = 1/H2O4S/c1-5(2,3)4/h(H2,1,2,3,4)/p-2
| InChIKey = QAOWNCQODCNURD-NUQVWONBAM
| StdInChI = 1S/H2O4S/c1-5(2,3)4/h(H2,1,2,3,4)/p-2
| StdInChIKey = QAOWNCQODCNURD-UHFFFAOYSA-L
| RTECS = 
| MeSHName = 
| ChEBI = 16189 }}
|Section2={{Chembox Properties
| Formula = {{chem2|SO4(2-)}}
| S=1|O=4
| Appearance =
| ConjugateAcid = [[Hydrogensulfate]]
| Solubility = }}
|Section3={{Chembox Hazards
| MainHazards =
| FlashPt =
| AutoignitionPt = }}
}}

The '''sulfate''' or '''sulphate''' ion is a [[Polyatomic ion|polyatomic anion]] with the [[empirical formula]] {{chem2|SO4(2-)}}. Salts, acid derivatives, and [[peroxide]]s of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are [[salt (chemistry)|salt]]s of [[sulfuric acid]] and many are prepared from that acid.

==Spelling==
{{see|American and British English spelling differences}}
"Sulfate" is the spelling recommended by [[International Union of Pure and Applied Chemistry|IUPAC]], but "sulphate" was traditionally used in [[British English]].

==Structure==
The sulfate anion consists of a central [[sulfur]] atom surrounded by four equivalent [[oxygen]] atoms in a [[tetrahedron|tetrahedral]] arrangement. The symmetry of the isolated anion is the same as that of methane. The sulfur atom is in the +6 [[oxidation state]] while the four oxygen atoms are each in the −2 state. The sulfate ion carries an overall [[charge (physics)|charge]] of −2 and it is the [[conjugate acid|conjugate base]] of the '''bisulfate''' (or hydrogensulfate) ion, {{chem2|HSO4-}}, which is in turn the conjugate base of {{chem2|H2SO4}}, [[sulfuric acid]]. Organic [[sulfate ester]]s, such as [[dimethyl sulfate]], are covalent compounds and [[ester]]s of sulfuric acid. The [[tetrahedral molecular geometry]] of the sulfate ion is as predicted by [[VSEPR theory]].

==Bonding==
[[File:Sulfate covalent-ionic.svg|thumb|Two models of the sulfate ion.<br />'''1''' with [[Chemical polarity#polar molecules|polar covalent]] bonds only; '''2''' with an [[ionic bond]]]][[Image:Sulfate-resonance-2D.png|thumb|Six resonances]]
The first description of the bonding in modern terms was by [[Gilbert N. Lewis|Gilbert Lewis]] in his groundbreaking paper of 1916, where he described the bonding in terms of electron octets around each atom. There are two double bonds, and there is a [[formal charge]] of +2 on the sulfur atom and -1 on each oxygen atom.<ref>{{cite journal|title=The Atom and the Molecule|first=Gilbert N.|last=Lewis|author-link=Gilbert N. Lewis|journal=[[J. Am. Chem. Soc.]]|volume=38|date=1916|issue=4|pages=762–785|url=http://osulibrary.oregonstate.edu/specialcollections/coll/pauling/bond/papers/corr216.3-lewispub-19160400-18-large.html|doi=10.1021/ja02261a002|s2cid=95865413 }} (See page 778.)</ref>{{efn|Lewis assigned to sulfur a negative charge of two, starting from six own valence electrons and ending up with eight electrons shared with the oxygen atoms. In fact, sulfur donates two electrons to the oxygen atoms.|name=formal charge}}

Later, [[Linus Pauling]] used [[valence bond theory]] to propose that the most significant [[Resonance (chemistry)|resonance canonicals]] had two [[pi bond]]s involving d orbitals. His reasoning was that the charge on sulfur was thus reduced, in accordance with his [[Pauling's principle of electroneutrality|principle of electroneutrality]].<ref>{{cite journal|title=The modern theory of valency|first=Linus|last=Pauling|author-link=Linus Pauling|journal=[[J. Chem. Soc.]]|date=1948|volume=17|pages=1461–1467|doi=10.1039/JR9480001461|pmid=18893624|url=https://authors.library.caltech.edu/59671/}}</ref> The S−O bond length of 149&nbsp;pm is shorter than the bond lengths in [[sulfuric acid]] of 157&nbsp;pm for S−OH. The double bonding was taken by Pauling to account for the shortness of the S−O bond.

Pauling's use of d orbitals provoked a debate on the relative importance of [[pi bond]]ing and bond polarity ([[electrostatic attraction]]) in causing the shortening of the S−O bond. The outcome was a broad consensus that d orbitals play a role, but are not as significant as Pauling had believed.<ref>{{cite journal|first=C.&nbsp;A.|last=Coulson|title=d Electrons and Molecular Bonding|journal=[[Nature (journal)|Nature]]|volume=221|page=1106|date=1969|issue=5186|doi=10.1038/2211106a0|bibcode=1969Natur.221.1106C|s2cid=4162835}}</ref><ref>{{cite journal|first=K.&nbsp;A.&nbsp;R.|last=Mitchell|title=Use of outer d orbitals in bonding|journal=[[Chem. Rev.]] |volume=69|page=157|date=1969|issue=2|doi=10.1021/cr60258a001}}</ref>

A widely accepted description involving pπ&nbsp;–&nbsp;dπ bonding was initially proposed by [[Durward William John Cruickshank]]. In this model, fully occupied p orbitals on oxygen overlap with empty sulfur d orbitals (principally the d<sub>''z''<sup>2</sup></sub> and d<sub>''x''<sup>2</sup>–''y''<sup>2</sup></sub>).<ref name="cotton" /> However, in this description, despite there being some π character to the S−O bonds, the bond has significant ionic character. For sulfuric acid, computational analysis (with [[natural bond orbital]]s) confirms a clear positive charge on sulfur (theoretically +2.45) and a low 3d occupancy. Therefore, the representation with four single bonds is the optimal Lewis structure rather than the one with two double bonds (thus the Lewis model, not the Pauling model).<ref name="Stefan">{{cite journal|first1=Thorsten|last1=Stefan|first2=Rudolf|last2=Janoschek|title=How relevant are S=O and P=O Double Bonds for the Description of the Acid Molecules H<sub>2</sub>SO<sub>3</sub>, H<sub>2</sub>SO<sub>4</sub>, and H<sub>3</sub>PO<sub>4</sub>, respectively?|journal=J. Mol. Modeling|volume=6|issue=2|date=Feb 2000|pages=282–288|doi=10.1007/PL00010730|s2cid=96291857}}</ref> 

In this model, the structure obeys the [[octet rule]] and the charge distribution is in agreement with the [[electronegativity]] of the atoms. The discrepancy between the S−O bond length in the sulfate ion and the S−OH bond length in sulfuric acid is explained by donation of p-orbital electrons from the terminal S=O bonds in sulfuric acid into the antibonding S−OH orbitals, weakening them resulting in the longer bond length of the latter.

However, Pauling's representation for sulfate and other main group compounds with oxygen is still a common way of representing the bonding in many textbooks.<ref name="cotton">{{cite book|author1-link=F. Albert Cotton|last1=Cotton|first1=F. Albert|author2-link=Geoffrey Wilkinson|last2=Wilkinson|first2=Geoffrey|date=1966|title=Advanced Inorganic Chemistry|edition=2nd|location=New York, NY|publisher=Wiley}}</ref><ref name="greenwood" /> The apparent contradiction can be clarified if one realizes that the [[covalent bond|covalent]] double bonds in the Lewis structure actually represent bonds that are strongly polarized by more than 90% towards the oxygen atom. On the other hand, in the structure with a [[dipolar bond]], the charge is localized as a [[lone pair]] on the oxygen.<ref name="Stefan" />

==Preparation==
Typically [[metal sulfate]]s are prepared by treating metal oxides, metal carbonates, or the metal itself with [[sulfuric acid]]:<ref name=greenwood>{{Greenwood&Earnshaw}}</ref>
:{{chem2 | Zn + H2SO4 -> ZnSO4 + H2 }}
:{{chem2 | Cu(OH)2 + H2SO4 -> CuSO4 + 2 H2O }}
:{{chem2 | CdCO3 + H2SO4 -> CdSO4 + H2O + CO2 }}
Although written with simple anhydrous formulas, these conversions generally are conducted in the presence of water.  Consequently the product sulfates are [[water of crystallization|hydrated]], corresponding to [[zinc sulfate]] {{chem2|ZnSO4*7H2O}}, [[copper(II) sulfate]] {{chem2|CuSO4*5H2O}}, and [[cadmium sulfate]] {{chem2|CdSO4*H2O}}.

Some metal [[sulfide]]s can be oxidized to give metal sulfates.

==Properties==
There are numerous examples of ionic sulfates, many of which are highly [[solubility|soluble]] in [[water]]. Exceptions include [[calcium sulfate]], [[strontium sulfate]], [[lead(II) sulfate]], [[barium sulfate]], [[silver sulfate]], and [[mercury sulfate]], which are poorly soluble. [[Radium sulfate]] is the most insoluble sulfate known. The barium derivative is useful in the [[gravimetric analysis]] of sulfate: if one adds a solution of most barium salts, for instance [[barium chloride]], to a solution containing sulfate ions, barium sulfate will precipitate out of solution as a whitish powder. This is a common laboratory test to determine if sulfate anions are present.

The sulfate ion can act as a ligand attaching either by one oxygen (monodentate) or by two oxygens as either a [[chelate]] or a bridge.<ref name=greenwood/> An example is the complex {{chem2|[[Cobalt|Co]]([[Ethylenediamine|en]])2(SO4)]+Br−}}<ref name=greenwood/> or the neutral metal complex {{chem2|[[Platinum|Pt]]SO4([[Triphenylphosphine|PPh3]])2]}} where the sulfate ion is acting as a [[denticity|bidentate]] ligand. The metal–oxygen bonds in sulfate complexes can have significant covalent character.

==Uses and occurrence==

===Commercial applications===
[[File:Objectes de la Sala Horta i Marjal (27190138015).jpg|thumb|upright|Knapsack sprayer used to apply sulfate to vegetables. [[Valencian Museum of Ethnology]].]]
Sulfates are widely used industrially. Major compounds include:

* [[Gypsum]], the natural mineral form of hydrated [[calcium sulfate]], is used to produce [[plaster]]. About 100 million tonnes per year are used by the construction industry.
* [[Copper sulfate]], a common [[algaecide]], the more stable form ([[Copper(II) sulfate|{{chem2|CuSO4}}]]) is used for galvanic cells as electrolyte
* [[Iron(II) sulfate]], a common form of iron in mineral supplements for humans, animals, and soil for plants
* [[Magnesium sulfate]] (commonly known as [[Epsom salts]]), used in therapeutic baths
* [[Lead(II) sulfate]], produced on both plates during the discharge of a [[lead–acid battery]]
* [[Sodium laureth sulfate]], or SLES, a common [[detergent]] in shampoo formulations
* [[Polyhalite]], {{chem2|K2Ca2Mg(SO4)4*2H2O}}, used as [[fertiliser]].

===Occurrence in nature===
[[Sulfate-reducing bacteria]], some anaerobic microorganisms, such as those living in sediment or near deep sea thermal vents, use the reduction of sulfates coupled with the oxidation of organic compounds or hydrogen as an energy source for chemosynthesis.

==History==
Some sulfates were known to alchemists. The vitriol salts, from the Latin ''vitreolum'', glassy, were so-called because they were some of the first transparent crystals known.<ref>{{cite book|title=Inorganic and Theoretical Chemistry|first=F. Sherwood|last=Taylor|edition=6th|date=1942|publisher=William Heinemann}}</ref> [[Green vitriol]] is [[iron]](II) sulfate heptahydrate, {{chem2|FeSO4*7H2O}}; [[blue vitriol]] is [[copper]](II) sulfate pentahydrate, {{chem2|CuSO4*5H2O}} and [[white vitriol]] is zinc sulfate heptahydrate, {{chem2|ZnSO4*7H2O}}. [[Alum]], a double sulfate of [[potassium]] and [[aluminium]] with the formula {{chem2|K2Al2(SO4)4*24H2O}}, figured in the development of the chemical industry.

==Environmental effects==
Sulfates occur as microscopic particles ([[Particulate|aerosols]]) resulting from [[fossil fuel]] and [[biomass]] combustion. They increase the acidity of the [[Earth's atmosphere|atmosphere]] and form [[acid rain]]. <!-- do sulfate aerosols per se comprise "acid rain" vs. aerobic oxidation of SO2 and SO3 to give H2SO4--> The [[Anaerobic organism|anaerobic]] [[sulfate-reducing bacteria]] ''[[Desulfovibrio]] desulfuricans'' and ''[[Desulfovibrio vulgaris|D. vulgaris]]'' can remove the black [[sulfate crust]] that often tarnishes buildings.<ref>{{cite journal|date= Nov 2006| pages=1075–1079| title=Saving a fragile legacy. Biotechnology and microbiology are increasingly used to preserve and restore the worlds cultural heritage| author=Andrea Rinaldi| journal=EMBO Reports| pmc=1679785| pmid=17077862| doi=10.1038/sj.embor.7400844| volume=7| issue=11}}</ref>

===Main effects on climate===
[[Image:Climate Change Attribution.png|thumb|250px|This figure shows the level of agreement between a [[climate model]] driven by five factors and the [[historical temperature record]]. The negative component identified as "sulfate" is associated with the aerosol emissions blamed for global dimming.]]
{{excerpt|Global dimming#History|paragraph=2}}
[[File:SulufrDioxide2017.png|thumb|left|Sulfur dioxide in the world on April 15, 2017. Note that sulfur dioxide moves through the atmosphere with prevailing winds and thus local sulfur dioxide distributions vary day to day with weather patterns and seasonality.]]
{{excerpt|Global dimming#Causes|paragraph=1|hat=no|files=no}}

====Reversal and accelerated warming====
{{excerpt|Global dimming#Reversal|paragraph=1}}
{{excerpt|Global dimming#Historical cooling|hat=no|files=no}}

{{excerpt|Global dimming#Future|paragraphs=1,3|hat=no|files=no}}

====Hydrological cycle====
{{excerpt|Global dimming#Relationship with water cycle|paragraph=1}}

====Solar geoengineering====
[[File:SPICE SRM overview.jpg|thumb|upright=1.5|alt=refer to caption and image description|Proposed tethered balloon to inject [[aerosols]] into the stratosphere.]]
As the real world had shown the importance of sulfate aerosol concentrations to the global climate, research into the subject accelerated.  Formation of the aerosols and their effects on the atmosphere can be studied in the lab, with methods like [[Ion chromatography|ion-chromatography]] and [[mass spectrometry]]<ref>{{Cite journal |last1=Kobayashi |first1=Yuya |last2=Ide |first2=Yu |last3=Takegawa |first3=Nobuyuki |date=3 April 2021 |title=Development of a novel particle mass spectrometer for online measurements of refractory sulfate aerosols |url=https://doi.org/10.1080/02786826.2020.1852168 |journal=Aerosol Science and Technology |volume=55 |issue=4 |pages=371–386 |doi=10.1080/02786826.2020.1852168 |bibcode=2021AerST..55..371K |s2cid=229506768 |issn=0278-6826}}</ref> Samples of actual particles can be recovered from the [[stratosphere]] using balloons or aircraft,<ref>{{cite journal |url=https://www.researchgate.net/publication/234296252_DUSTER_Aerosol_collection_in_the_stratosphere |journal=Societa Astronomica Italiana |title=The DUSTER experiment: collection and analysis of aerosol in the high stratosphere |author1=Palumbo, P. |author2= A. Rotundi |author3=V. Della Corte |author4=A. Ciucci |author5=L. Colangeli |author6=F. Esposito |author7=E. Mazzotta Epifani |author8=V. Mennella |author9=J.R. Brucato |author10=F.J.M. Rietmeijer |author11=G. J. Flynn |author12=J.-B. Renard   |author13=J.R. Stephens |author14=E. Zona |access-date=19 February 2009 }}</ref> and remote [[satellite]]s were also used for observation.<ref name=":32">{{Cite journal |last1=Myhre |first1=Gunnar |last2=Stordal |first2=Frode |last3=Berglen |first3=Tore F. |last4=Sundet |first4=Jostein K. |last5=Isaksen |first5=Ivar S. A. |date=1 March 2004 |title=Uncertainties in the Radiative Forcing Due to Sulfate Aerosols |journal=Journal of the Atmospheric Sciences |language=EN |volume=61 |issue=5 |pages=485–498 |doi=10.1175/1520-0469(2004)061<0485:UITRFD>2.0.CO;2 |bibcode=2004JAtS...61..485M |s2cid=55623817 |issn=0022-4928|doi-access=free }}</ref> This data is fed into the [[climate model]]s,<ref>{{Cite journal |last1=Zhang |first1=Jie |last2=Furtado |first2=Kalli |last3=Turnock |first3=Steven T. |last4=Mulcahy |first4=Jane P. |last5=Wilcox |first5=Laura J. |last6=Booth |first6=Ben B. |last7=Sexton |first7=David |last8=Wu |first8=Tongwen |last9=Zhang |first9=Fang |last10=Liu |first10=Qianxia |date=22 December 2021 |title=The role of anthropogenic aerosols in the anomalous cooling from 1960 to 1990 in the CMIP6 Earth system models |url=https://acp.copernicus.org/articles/21/18609/2021/ |journal=Atmospheric Chemistry and Physics |volume=21 |issue=4 |pages=18609–18627 |language=en |doi=10.5194/acp-21-18609-2021 |bibcode=2021ACP....2118609Z |doi-access=free }}</ref> as the necessity of accounting for aerosol cooling to truly understand the rate and evolution of warming had long been apparent, with the [[IPCC Second Assessment Report]] being the first to include an estimate of their impact on climate, and every major model able to simulate them by the time [[IPCC Fourth Assessment Report]] was published in 2007.<ref>{{cite web|url=https://earthobservatory.nasa.gov/features/Aerosols/page3.php|title=Aerosols and Incoming Sunlight (Direct Effects)|publisher=[[NASA]]|date=2 November 2010}}</ref> Many scientists also see the other side of this research, which is learning how to cause the same effect artificially.<ref>{{cite web |url=https://www.sciencedaily.com/releases/2006/09/060914182715.htm |title=Stratospheric Injections Could Help Cool Earth, Computer Model Shows | access-date=19 February 2009 |publisher=ScienceDaily |date=15 September 2006 }}</ref> While discussed around the 1990s, if not earlier,<ref>{{cite journal |journal=Phil. Trans. R. Soc. A |year=1996 |volume=366 |pages=4039–56 |title=Global and Arctic climate engineering: numerical model studies |doi=10.1098/rsta.2008.0132 |author1=Launder B. |author2=J.M.T. Thompson |pmid=18757275 |issue=1882 |bibcode=2008RSPTA.366.4039C|doi-access=free }}</ref> stratospheric aerosol injection as a [[solar geoengineering]] method is best associated with [[Paul Crutzen]]'s detailed 2006 proposal.<ref name="Crutzen062" /> Deploying in the stratosphere ensures that the aerosols are at their most effective, and that the progress of clean air measures would not be reversed: more recent research estimated that even under the highest-emission scenario [[Representative Concentration Pathway|RCP 8.5]],  the addition of stratospheric sulfur required to avoid {{convert|4|C-change|F-change}} relative to now (and {{convert|5|C-change|F-change}} relative to the preindustrial) would be effectively offset by the future controls on tropospheric sulfate pollution, and the amount required would be even less for less drastic warming scenarios.<ref name="Visioni2020">{{Cite journal|last1=Visioni|first1=Daniele|last2=Slessarev|first2=Eric |last3=MacMartin|first3=Douglas G|last4=Mahowald|first4=Natalie M|last5=Goodale|first5=Christine L|last6=Xia|first6=Lili|date=1 September 2020|title=What goes up must come down: impacts of deposition in a sulfate geoengineering scenario|journal=Environmental Research Letters|volume=15|issue=9|pages=094063|doi=10.1088/1748-9326/ab94eb|bibcode=2020ERL....15i4063V|issn=1748-9326|doi-access=free}}</ref> This spurred a detailed look at its costs and benefits,<ref>{{cite web |url=http://www.met.reading.ac.uk/pg-research/downloads/2009/pgr-charlton.pdf |title=Costs and benefits of geo-engineering in the Stratosphere |author1=Andrew Charlton-Perez |author2=Eleanor Highwood |access-date=17 February 2009 |archive-date=14 January 2017 |archive-url=https://web.archive.org/web/20170114032949/http://www.met.reading.ac.uk/pg-research/downloads/2009/pgr-charlton.pdf |url-status=dead }}</ref> but even with hundreds of studies into the subject completed by the early 2020s, some notable uncertainties remain.<ref name="IPCC_WGI_SRM" >{{Cite journal |last1=Trisos |first1=Christopher H. |last2=Geden |first2=Oliver |last3=Seneviratne |first3=Sonia I. |last4=Sugiyama |first4=Masahiro |last5=van Aalst |first5=Maarten |last6=Bala |first6=Govindasamy |last7=Mach |first7=Katharine J. |last8=Ginzburg |first8=Veronika |last9=de Coninck |first9=Heleen |last10=Patt |first10=Anthony |title=Cross-Working Group Box SRM: Solar Radiation Modification |url=https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_Chapter16.pdf |journal=Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change |year=2021 |volume=2021 |pages=1238 |doi=10.1017/9781009157896.007|bibcode=2021AGUFM.U13B..05K }}</ref>

==Hydrogensulfate (bisulfate)==
{{chembox
| ImageFile1 = Hydrogen sulfate.svg
| ImageSize1 = 120px
| ImageAlt1 = Hydrogen sulfate (bisulfate)
| IUPACName = Hydrogensulfate<ref>{{Citation|url = http://old.iupac.org/publications/books/rbook/Red_Book_2005.pdf|title = Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005|publisher = IUPAC|page = 129|url-status = live|archive-url = https://web.archive.org/web/20170518230415/http://old.iupac.org/publications/books/rbook/Red_Book_2005.pdf|archive-date = 2017-05-18}}</ref>
| OtherNames = Bisulfate
| Name = Hydrogensulfate
|Section1={{Chembox Identifiers
| ChEBI = 45696
| ChemSpiderID = 55666
| CASNo = 14996-02-2
| Gmelin = 2121
| PubChem = 61778
| SMILES = O[S](=O)(=O)[O-]
| StdInChI=1S/H2O4S/c1-5(2,3)4/h(H2,1,2,3,4)/p-1
| StdInChIKey = QAOWNCQODCNURD-UHFFFAOYSA-M
  }}
|Section2={{Chembox Properties
| Formula = {{chem2|HSO4−}}
| MolarMass = 97.071 g/mol
| ConjugateAcid = [[Sulfuric acid]]
| ConjugateBase = Sulfate
  }}
}}
<!-- bisulfate redirects here -->
The '''hydrogensulfate''' ion ({{chem2|HSO4-}}), also called the '''bisulfate''' ion, is the [[Conjugate (acid-base theory)|conjugate base]] of [[sulfuric acid]] ({{chem2|H2SO4}}).<ref>{{Citation|url = http://old.iupac.org/publications/books/rbook/Red_Book_2005.pdf|title = Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005|publisher = IUPAC|page = 129|url-status = live|archive-url = https://web.archive.org/web/20170518230415/http://old.iupac.org/publications/books/rbook/Red_Book_2005.pdf|archive-date = 2017-05-18}}</ref>{{efn|The prefix "bi" in "bisulfate" comes from an outdated naming system and is based on the observation that there is twice as much sulfate ({{chem2|SO4(2-)}}) in [[sodium bisulfate]] ({{chem2|NaHSO4}}) and other bisulfates as in [[sodium sulfate]] ({{chem2|Na2SO4}}) and other sulfates. See also [[bicarbonate]].}} Sulfuric acid is classified as a strong acid; in aqueous solutions it ionizes completely to form [[hydronium]] ({{chem2|H3O+}}) and hydrogensulfate ({{chem2|HSO4-}}) ions. In other words, the sulfuric acid behaves as a [[Brønsted–Lowry acid–base theory|Brønsted–Lowry acid]] and is [[deprotonation|deprotonated]] to form hydrogensulfate ion. Hydrogensulfate has a [[Valence (chemistry)|valency]] of 1. An example of a salt containing the {{chem2|HSO4-}} ion is [[sodium bisulfate]], {{chem2|NaHSO4}}. In dilute solutions the hydrogensulfate ions also dissociate, forming more hydronium ions and sulfate ions ({{chem2|SO4(2-)}}).

== Other sulfur oxyanions ==
{|class="wikitable"
|+Sulfur oxyanions
! Molecular formula
! Name
|-
|{{chem2|SO5(2-)}}|| [[Peroxomonosulfate]]
|-
|{{chem2|SO4(2-)}} || Sulfate
|-
|{{chem2|SO3(2-)}} || [[Sulfite]]
|-
|{{chem2|S2O8(2-)}} || [[Peroxydisulfate]]
|-
|{{chem2|S2O7(2-)}} || [[Pyrosulfate]]
|-
|{{chem2|S2O6(2-)}} || [[Dithionate]]
|-
|{{chem2|S2O5(2-)}} || [[Metabisulfite]]
|-
|{{chem2|S2O4(2-)}} || [[Dithionite]]
|-
|{{chem2|S2O3(2-)}} || [[Thiosulfate]]
|-
|{{chem2|S3O6(2-)}} || [[Trithionate]]
|-
|{{chem2|S4O6(2-)}} || [[Tetrathionate]]
|}

{{clear}}
== See also ==
* [[Sulfonate]]
* [[Lead-acid battery#Sulfation and desulfation|Sulfation and desulfation of lead–acid batteries]]
* [[Sulfate-reducing microorganism]]

== Notes ==
{{notelist}}

==References==
{{Reflist|30em}}
{{Authority control}}

{{Sulfates}}

==External links==
*[https://earth.nullschool.net/#current/particulates/surface/level/overlay=suexttau/winkel3 Current global map of aerosol optical thickness]

[[Category:Sulfates| ]]
[[Category:Particulates]]
[[Category:Sulfur oxyanions]]