View source for Chemistry:Manganese

{{Short description|Chemical element with atomic number 25}}
{{Infobox manganese}}

'''Manganese''' is a [[Chemistry:Chemical element|chemical element]]; it has [[Chemistry:Symbol|symbol]] '''Mn''' and [[Physics:Atomic number|atomic number]] 25. It is a hard, brittle, silvery metal, often found in [[Earth:Mineral|mineral]]s in combination with [[Chemistry:Iron|iron]]. Manganese was first isolated in the 1770s.<!--Gahn surely did so in 1774, but there is some dispute over whether Ignaz Gottfried Kaim hadn't already done it in 1770--> Manganese is a [[Chemistry:Transition metal|transition metal]] with a multifaceted array of industrial [[Chemistry:Alloy|alloy]] uses, particularly in [[Chemistry:Stainless steel|stainless steel]]s. It improves strength, workability, and resistance to wear. Manganese oxide is used as an oxidising agent; as a rubber additive; and in glass making, fertilisers, and ceramics. Manganese sulfate can be used as a fungicide.

Manganese is also an essential human dietary element, important in macronutrient metabolism, bone formation, and [[Biology:Free radical|free radical]] defense systems. It is a critical component in dozens of proteins and enzymes.<ref name="Erikson-2019" /> It is found mostly in the bones, but also the liver, kidneys, and brain.<ref name="Emsley2001" /> In the human brain, the manganese is bound to manganese [[Biology:Metalloprotein|metalloprotein]]s, most notably [[Biology:Glutamine synthetase|glutamine synthetase]] in [[Biology:Astrocyte|astrocyte]]s.

It is familiar in the laboratory in the form of the deep violet salt [[Chemistry:Potassium permanganate|potassium permanganate]]. It occurs at the [[Biology:Active site|active site]]s in some [[Biology:Enzymes|enzymes]].<ref>{{cite book|last1=Roth |first1=Jerome |last2=Ponzoni |first2=Silvia |last3=Aschner |first3=Michael|chapter=Manganese Homeostasis and Transport |editor1-first=Lucia |editor1-last=Banci |series=Metal Ions in Life Sciences |volume=12|pages=169–201 |title=Metallomics and the Cell |date=2013 |publisher=Springer |isbn=978-94-007-5560-4 |doi=10.1007/978-94-007-5561-1_6 |pmid=23595673 |pmc=6542352 }} Electronic-book {{ISBN|978-94-007-5561-1}}.</ref> Of particular interest is the use of a Mn-O [[Chemistry:Atom cluster|cluster]], the [[Biology:Oxygen-evolving complex|oxygen-evolving complex]], in the production of oxygen by plants.

==Characteristics==

===Physical properties===
Manganese is a silvery-gray [[Chemistry:Metal|metal]] that resembles iron. It is hard and very brittle, difficult to fuse, but easy to oxidize.<ref name="Holl">{{cite book|publisher=Walter de Gruyter|date=1985|edition=91–100 |pages=1110–1117|isbn=978-3-11-007511-3|title=Lehrbuch der Anorganischen Chemie|first=Arnold F.|last=Holleman|author2=Wiberg, Egon|author3=Wiberg, Nils|language=de|chapter=Mangan}}</ref> Manganese metal and its common ions are [[Physics:Paramagnetic|paramagnetic]].<ref name="magnet">{{cite book |url=https://archive.org/details/crchandbookofche81lide |url-status=dead |title=Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics |publisher=CRC press |isbn=978-0-8493-0485-9 |first=David R. |last=Lide |date=2004 |url-access=registration |access-date=7 September 2019 |archive-url=https://web.archive.org/web/20191217023342/https://archive.org/details/crchandbookofche81lide |archive-date=17 December 2019 }}</ref> Manganese tarnishes slowly in air and oxidizes ("rusts") like iron in water containing dissolved oxygen.{{Citation needed|date=February 2023}}

===Isotopes===
{{Main|Physics:Isotopes of manganese}}
Naturally occurring manganese is composed of one stable [[Physics:Isotope|isotope]], <sup>55</sup>Mn. Several radioisotopes have been isolated and described, ranging in [[Physics:Atomic weight|atomic weight]] from 46 u (<sup>46</sup>Mn) to 72 u (<sup>72</sup>Mn). The most stable are <sup>53</sup>Mn with a [[Physics:Half-life|half-life]] of 3.7&nbsp;million years, <sup>54</sup>Mn with a half-life of 312.2 days, and <sup>52</sup>Mn with a half-life of 5.591 days. All of the remaining [[Physics:Radioactive|radioactive]] isotopes have half-lives of less than three hours, and the majority of less than one minute. The primary decay mode in isotopes lighter than the most abundant stable isotope, <sup>55</sup>Mn, is [[Physics:Electron capture|electron capture]] and the primary mode in heavier isotopes is [[Physics:Beta decay|beta decay]].<ref name="Audi" /> Manganese also has three meta states.<ref name="Audi">{{NUBASE2016}}</ref>

Manganese is part of the [[Physics:Iron group|iron group]] of elements, which are thought to be synthesized in large [[Astronomy:Star|star]]s shortly before the [[Astronomy:Supernova|supernova]] explosion.<ref>{{cite web |url=https://www.science.org/content/article/galaxy-s-brightest-explosions-go-nuclear-unexpected-trigger-pairs-dead-stars |title=The galaxy's brightest explosions go nuclear with an unexpected trigger: pairs of dead stars |work=Science |last=Clery |first=Daniel |date=4 June 2020 |access-date=26 July 2021 }}</ref> <sup>53</sup>Mn decays to <sup>53</sup>Cr with a half-life of 3.7&nbsp;million years. Because of its relatively short half-life, <sup>53</sup>Mn is relatively rare, produced by cosmic rays impact on [[Chemistry:Iron|iron]].<ref>{{cite journal |last1=Schaefer |first1=Jeorg|last2=Faestermann |first2=Thomas |title=Terrestrial manganese-53 – A new monitor of Earth surface processes |journal=Earth and Planetary Science Letters|volume=251|issue=3–4 |pages=334–345|date=2006 |doi=10.1016/j.epsl.2006.09.016 |bibcode=2006E&PSL.251..334S |last3=Herzog |first3=Gregory F. |last4=Knie |first4=Klaus |last5=Korschinek |first5=Gunther |last6=Masarik |first6=Jozef |last7=Meier |first7=Astrid |last8=Poutivtsev |first8=Michail |last9=Rugel |first9=Georg |last10=Schlüchter |first10=Christian |last11=Serifiddin |first11=Feride |last12=Winckler |first12=Gisela}}</ref> Manganese isotopic contents are typically combined with [[Chemistry:Chromium|chromium]] isotopic contents and have found application in isotope geology and [[Physics:Radiometric dating|radiometric dating]]. Mn–Cr isotopic ratios reinforce the evidence from [[Physics:Aluminium-26|<sup>26</sup>Al]] and [[Physics:Palladium-107|<sup>107</sup>Pd]] for the early history of the [[Astronomy:Solar System|Solar System]]. Variations in <sup>53</sup>Cr/<sup>52</sup>Cr and Mn/Cr ratios from several [[Astronomy:Meteorite|meteorite]]s suggest an initial <sup>53</sup>Mn/<sup>55</sup>Mn ratio, which indicate that Mn–Cr isotopic composition must result from ''in situ'' decay of <sup>53</sup>Mn in differentiated planetary bodies. Hence, <sup>53</sup>Mn provides additional evidence for [[Physics:Nucleosynthesis|nucleosynthetic]] processes immediately before coalescence of the Solar System.<ref>{{cite journal|doi=10.1016/S0016-7037(99)00312-9 |title=53Mn-53Cr evolution of the early solar system|year=1999|last1=Birck|first1=J. |last2=Rotaru|last3=Allègre|journal=Geochimica et Cosmochimica Acta|volume=63|pages=4111–4117|first2=M.|first3=C.|bibcode=1999GeCoA..63.4111B |issue=23–24}}</ref><ref>{{cite journal |doi=10.1016/S0016-7037(98)00189-6|title=Early solar system timescales according to 53Mn-53Cr systematics |year=1998|last1=Lugmair |first1=G.|journal=Geochimica et Cosmochimica Acta|volume=62|pages=2863–2886|bibcode=1998GeCoA..62.2863L|issue=16 |last2=Shukolyukov |first2=A.}}</ref><ref>{{cite journal|doi=10.1023/A:1005243228503|title=On The 53Mn Heterogeneity In The Early Solar System|year=2000|last1=Shukolyukov|first1=Alexander|last2=Lugmair |journal=Space Science Reviews|volume=92|pages=225–236|first2=Günter W.|bibcode=2000SSRv...92..225S}}</ref><ref>{{cite journal |doi=10.1016/j.gca.2008.03.023|title=53Mn–53Cr systematics of the early Solar System revisited|year=2008|last1=Trinquier|first1=A. |last2=Birck|last3=Allègre|last4=Göpel|last5=Ulfbeck |journal=Geochimica et Cosmochimica Acta|volume=72|pages=5146–5163|first2=J.|first3=C. |first4=C.|first5=D.|bibcode=2008GeCoA..72.5146T |issue=20}}</ref>

===Allotropes===
{|align=right
| [[File:Alpha-Mn.png|thumb|x160px|Unit cell of an α-Mn crystal]]
| [[File:Beta-Mn.png|thumb|x160px|Unit cell of a β-Mn crystal]]
|}
Four [[Physics:Allotropy|allotropes]] (structural forms) of solid manganese are known, labeled α, β, γ and δ, and occurring at successively higher temperatures. All are metallic, stable at standard pressure, and have a cubic crystal lattice, but they vary widely in their atomic structures.<ref name="Young 1975">{{cite journal |last1=Young |first1=D.A. |title=Phase diagrams of the elements |url=https://inis.iaea.org/search/search.aspx?orig_q=RN:7255152 |website=International Nuclear Information System |publisher=LNL |access-date=30 January 2023 |page=15 |date=1975}}</ref><ref name="Dhananjayan 1969">{{cite book |last1=Dhananjayan |first1=N. |last2=Banerjee |first2=T. |title=Crystallographic modifications of manganese and their transformation characteristics. ''Chapter 1 of:'' Structure of Electro-Deposited Manganese. |date=1969 |pages=3–28 |publisher=CSIR-NML |url=https://eprints.nmlindia.org/5609/}}</ref><ref name="Kemmitt 1973">{{cite book | last1=Kemmitt | first1=R. D. W. | last2=Peacock | first2=R. D. | title=The Chemistry of Manganese, Technetium and Rhenium. Pergamon Texts in Inorganic Chemistry. | publisher=Elsevier Science | publication-place=Saint Louis | date=1973 | isbn=978-1-4831-3806-0 | oclc=961064866 | page=778}}</ref>

'''Alpha manganese''' (α-Mn) is the equilibrium phase at room temperature. It has a body-centered cubic lattice and is unusual among elemental metals in having a very complex unit cell, with 58 atoms per cell (29 atoms per primitive unit cell) in four different types of site.<ref name="Bradley 1927">{{cite journal | first1=A.J. | last1=Bradley | first2=J. | last2=Thewlis | title=The crystal structure of α-manganese | journal=Proceedings of the Royal Society of London, Series A | volume=115 | issue=771 | year=1927 | issn=0950-1207 | doi=10.1098/rspa.1927.0103 | pages=456–471| bibcode=1927RSPSA.115..456B | doi-access=free }}</ref><ref name="Young 1975" /> It is [[Physics:Paramagnetic|paramagnetic]] at room temperature and [[Physics:Antiferromagnetic|antiferromagnetic]] at temperatures below {{convert|95|K|C|sigfig=3}}.<ref name="Lawson 1994">{{cite journal | last1=Lawson | first1=A. C. | last2=Larson | first2=Allen C. | last3=Aronson | first3=M. C. | display-authors=0 | title=Magnetic and crystallographic order in α-manganese | journal=J. Appl. Phys. | volume=76 | issue=10 | date=1994 | pages=7049–7051 | issn=0021-8979 | doi=10.1063/1.358024| bibcode=1994JAP....76.7049L }}</ref>

{|align=right
|[[File:Phase diagram of manganese (1975).png|thumb|190px|Phase diagram of manganese<ref name="Young 1975" />]]
|}
'''Beta manganese''' (β-Mn) forms when heated above the transition temperature of {{convert|973|K|C F|sigfig=3}}<!-- For the α-β transition, "Young 1975" gives about 1000 K; "Kemmitt 1973" gives 700±3 C (973 K)-->.  It has a primitive cubic structure with 20 atoms per unit cell at two types of sites, which is as complex as that of any other elemental metal.<ref name="Prior 2004">{{cite journal | last1=Prior | first1=Timothy J | last2=Nguyen-Manh | first2=Duc | last3=Couper | first3=Victoria J | last4=Battle | first4=Peter D | title=Ferromagnetism in the beta-manganese structure: Fe<sub>1.5</sub>Pd<sub>0.5</sub>Mo<sub>3</sub>N | journal=Journal of Physics: Condensed Matter | volume=16 | issue=13 | date=2004 | issn=0953-8984 | doi=10.1088/0953-8984/16/13/008 | pages=2273–2281| bibcode=2004JPCM...16.2273P | s2cid=250784683 }}</ref> It is easily obtained as a metastable phase at room temperature by rapid quenching. It does not show [[Physics:Magnetism|magnetic ordering]], remaining paramagnetic down to the lowest temperature measured (1.1&nbsp;K).<ref name="Prior 2004" /><ref name="Funahashi 1984">{{cite journal | last1=Funahashi | first1=S. | last2=Kohara | first2=T. | title=Neutron diffuse scattering in β-manganese | journal=J. Appl. Phys. | volume=55 | issue=6 | date=1984 | issn=0021-8979 | doi=10.1063/1.333561 | pages=2048–2050| bibcode=1984JAP....55.2048F }}</ref><ref name="Duschanek 1989">{{cite journal | last1=Duschanek | first1=H. | last2=Mohn | first2=P. | last3=Schwarz | first3=K. | title=Antiferromagnetic and ferromagnetic gamma-manganese generalisation of the fixed-spin-moment method | journal=Physica B: Condensed Matter | volume=161 | issue=1–3 | year=1989 | issn=0921-4526 | doi=10.1016/0921-4526(89)90120-8 | pages=139–142}}</ref>

'''Gamma manganese''' (γ-Mn) forms when heated above {{convert|1370|K|C F|sigfig=3}}.<!-- For the beta-gamma transition, "Duschanek 1989" gives 1368 K; "Garlen 2015" gives 1373 K; both round to 1370 K --> It has a simple face-centered cubic structure (four atoms per unit cell). When quenched to room temperature it converts to β-Mn, but it can be stabilized at room temperature by alloying it with at least 5 percent of other elements (such as C, Fe, Ni, Cu, Pd or Au), and these solute-stabilized alloys distort into a face-centered [[Physics:Tetragonal crystal system|tetragonal]] structure.<ref name="Bacon 1970">{{cite journal | last1=Bacon | first1=G E | last2=Cowlam | first2=N | title=A study of some alloys of gamma -manganese by neutron diffraction | journal=Journal of Physics C: Solid State Physics | volume=3 | issue=3 | date=1970| issn=0022-3719 | doi=10.1088/0022-3719/3/3/023 | pages=675–686| bibcode=1970JPhC....3..675B }}</ref><ref name="Duschanek 1989">{{cite journal | last1=Duschanek | first1=H. | last2=Mohn | first2=P. | last3=Schwarz | first3=K. | title=Antiferromagnetic and ferromagnetic gamma-manganese generalisation of the fixed-spin-moment method | journal=Physica B: Condensed Matter | volume=161 | issue=1–3 | year=1989 | issn=0921-4526 | doi=10.1016/0921-4526(89)90120-8 | pages=139–142}}</ref>

'''Delta manganese''' (δ-Mn) forms when heated above {{convert|1406|K|C F|sigfig=3}}<!-- For the γ-δ transition, "Dhananjayan 1969" says 1134 C (= approx 1407 K); "Duschanek 1989" indicates 1406 K; "Young 1975" shows about 1400±20 K in the phase diagram (though its text states "near 1520 K", which seems to be a typo because it matches the melting point, not the gamma-delta transition). --> and is stable up to the manganese melting point of {{convert|1519|K|C F|sigfig=3}}. It has a body-centered cubic structure (two atoms per cubic unit cell).<ref name="Dhananjayan 1969" /><ref name="Duschanek 1989" />

==Chemical compounds==
[[File:Chlorid manganatý.JPG|thumb|left|upright|[[Chemistry:Manganese(II) chloride|Manganese(II) chloride]] crystals – the pale pink color of Mn(II) salts is due to a spin-forbidden 3d transition.<ref>{{cite book|title=Shriver and Atkins' Inorganic Chemistry|date=2010|publisher=Oxford University Press|isbn=978-0-19-923617-6|chapter=Ch. 20}}</ref>]]

Common [[Chemistry:Oxidation state|oxidation state]]s of manganese are +2, +3, +4, +6, and +7, although all oxidation states from −3 to +7 except –2 have been observed. Manganese in oxidation state +7 is represented by salts of the intensely purple permanganate anion MnO<sub>4</sub><sup>−</sup>. [[Chemistry:Potassium permanganate|Potassium permanganate]] is a commonly used laboratory [[Biology:Reagent|reagent]] because of its oxidizing properties; it is used as a topical medicine (for example, in the treatment of fish diseases). Solutions of potassium permanganate were among the first stains and fixatives to be used in the preparation of biological cells and tissues for electron microscopy.<ref>{{cite journal |doi=10.1083/jcb.2.6.799 |last=Luft |first=J. H.|date=1956 |title=Permanganate – a new fixative for electron microscopy |journal=Journal of Biophysical and Biochemical Cytology |volume=2 |pages=799–802 |pmid=13398447 |issue=6 |pmc=2224005}}</ref>

Aside from various permanganate salts, Mn(VII) is represented by the unstable, volatile derivative Mn<sub>2</sub>O<sub>7</sub>. Oxyhalides (MnO<sub>3</sub>F and MnO<sub>3</sub>Cl) are powerful oxidizing agents.<ref name="Holl" />  The most prominent example of Mn in the +6 oxidation state is the green anion [[Chemistry:Manganate|manganate]], [MnO<sub>4</sub>]<sup>2-</sup>.  Manganate salts are intermediates in the extraction of manganese from its ores.  Compounds with oxidation states +5 are somewhat elusive, one example is the blue anion [[Chemistry:Hypomanganate|hypomanganate]] [MnO<sub>4</sub>]<sup>3-</sup>.

Compounds with Mn in oxidation state +5 are rarely encountered and often found associated with an oxide (O<sup>2-</sup>) or [[Chemistry:Nitride|nitride]] (N<sup>3-</sup>) ligand.<ref>{{cite journal |doi=10.1021/ar400147y|title=Reactivity of Nitrido Complexes of Ruthenium(VI), Osmium(VI), and Manganese(V) Bearing Schiff Base and Simple Anionic Ligands |year=2014 |last1=Man |first1=Wai-Lun |last2=Lam |first2=William W. Y. |last3=Lau |first3=Tai-Chu |journal=Accounts of Chemical Research |volume=47 |issue=2 |pages=427–439 |pmid=24047467 }}</ref><ref>{{cite journal |doi=10.1021/ar700039y|title=Corrolazines: New Frontiers in High-Valent Metalloporphyrinoid Stability and Reactivity |year=2007 |last1=Goldberg |first1=David P. |journal=Accounts of Chemical Research |volume=40 |issue=7 |pages=626–634 |pmid=17580977 }}</ref>

Mn(IV) is somewhat enigmatic because it is common in nature but far rarer in synthetic chemistry. The most common Mn ore, [[Chemistry:Pyrolusite|pyrolusite]], is MnO<sub>2</sub>.  It is the dark brown pigment of many cave drawings but is also a common ingredient in [[Chemistry:Dry cell|dry cell]] batteries.  Complexes of Mn(IV) are well known, but they require elaborate ligands. Mn(IV)-OH complexes are an intermediate in some [[Biology:Enzyme|enzyme]]s, including the oxygen evolving center (OEC) in plants.<ref>{{cite journal |doi=10.1021/cr4004874|title=Mn4Ca Cluster in Photosynthesis: Where and How Water is Oxidized to Dioxygen |year=2014 |last1=Yano |first1=Junko |last2=Yachandra |first2=Vittal |journal=Chemical Reviews |volume=114 |issue=8 |pages=4175–4205 |pmid=24684576 |pmc=4002066 }}</ref>

Simple derivatives Mn<sup>+3</sup> are rarely encountered but can be stabilized by suitably basic ligands.  [[Chemistry:Manganese(III) acetate|Manganese(III) acetate]] is an oxidant useful in [[Chemistry:Organic synthesis|organic synthesis]]. Solid compounds of manganese(III) are characterized by its strong purple-red color and a preference for distorted octahedral coordination resulting from the Jahn-Teller effect.{{citation needed|date=February 2023}}

[[File:KMnO4 in H2O.jpg|thumb|left|upright=0.55|Aqueous solution of KMnO<sub>4</sub> illustrating the deep purple of Mn(VII) as it occurs in permanganate]]
A particularly common oxidation state for manganese in aqueous solution is +2, which has a pale pink color. Many manganese(II) compounds are known, such as the aquo complexes derived from [[Chemistry:Manganese(II) sulfate|manganese(II) sulfate]] (MnSO<sub>4</sub>) and [[Chemistry:Manganese(II) chloride|manganese(II) chloride]] (MnCl<sub>2</sub>). This oxidation state is also seen in the mineral [[Chemistry:Rhodochrosite|rhodochrosite]] ([[Chemistry:Manganese(II) carbonate|manganese(II) carbonate]]). Manganese(II) commonly exists with a high spin, S = 5/2 ground state because of the high pairing energy for manganese(II). There are no spin-allowed d–d transitions in manganese(II), which explain its faint color.<ref>Rayner-Canham, Geoffrey and Overton, Tina (2003) ''Descriptive Inorganic Chemistry'', Macmillan, p. 491, {{ISBN|0-7167-4620-4}}.</ref>
{| class="wikitable floatright"
|-
! colspan=2|Oxidation states of manganese<ref name="Schmidt">{{cite book|title=Anorganische Chemie II.|chapter=VII. Nebengruppe |pages=100–109|first=Max|last=Schmidt|publisher=Wissenschaftsverlag|date=1968|language=de}}</ref>
|-
| −3 || {{chem|Mn(CO)(NO)|3|}}
|-
| −1 || [[Chemistry:Pentacarbonylhydridomanganese|{{chem|H|Mn|(CO)|5}}]]
|-
| 0 || [[Chemistry:Dimanganese decacarbonyl|{{chem|Mn|2|(CO)|10}}]]
|-
| +1 || [[Chemistry:Methylcyclopentadienyl manganese tricarbonyl|{{chem|MnC|5|H|4|CH|3|(CO)|3}}]]
|-
| '''+2''' || [[Chemistry:Manganese(II) chloride|{{chem|MnCl|2}}]], [[Chemistry:Manganese(II) carbonate|{{chem|MnCO|3}}]], [[Chemistry:Manganese(II) oxide|{{chem|MnO}}]]
|-
| '''+3''' || [[Chemistry:Manganese(III) fluoride|{{chem|MnF|3}}]], [[Chemistry:Manganese(III) acetate|{{chem|Mn(OAc)|3}}]], [[Chemistry:Manganese(III) oxide|{{chem|Mn|2|O|3}}]]
|-
| '''+4''' || [[Chemistry:Manganese dioxide|{{chem|MnO|2}}]]
|-
| +5 || [[Chemistry:Potassium hypomanganate|{{chem|K|3|MnO|4}}]]
|-
| '''+6''' || [[Chemistry:Potassium manganate|{{chem|K|2|MnO|4}}]]
|-
| '''+7''' || [[Chemistry:Potassium permanganate|{{chem|KMnO|4}}]], [[Chemistry:Manganese heptoxide|{{chem|Mn|2|O|7}}]]
|-
|colspan=2 style="font-size: smaller; text-align: center"|Common oxidation states are in bold.
|}

===Organomanganese compounds===
{{main|Chemistry:Organomanganese chemistry}}
Manganese forms a large variety of organometallic derivatives, i.e., compounds with Mn-C bonds. The organometallic derivatives include numerous examples of Mn in its lower oxidation states, i.e. Mn(-III) up through Mn(I). This area of organometallic chemistry is attractive because Mn is inexpensive and of relatively low toxicity.{{citation needed|date=February 2023}}

Of greatest commercial interest is "MMT", [[Chemistry:Methylcyclopentadienyl manganese tricarbonyl|methylcyclopentadienyl manganese tricarbonyl]], which is used as an anti-knock compound added to gasoline (petrol) in some countries.  It features Mn(I). Consistent with other aspects of Mn(II) chemistry, [[Chemistry:Manganocene|manganocene]] ({{chem2|Mn(C5H5)2}}) is high-spin.  In contrast, its neighboring metal iron forms an air-stable, low-spin derivative in the form of [[Chemistry:Ferrocene|ferrocene]] ({{chem2|Fe(C5H5)2}}).  When conducted under an atmosphere of [[Chemistry:Carbon monoxide|carbon monoxide]], reduction of Mn(II) salts gives [[Chemistry:Dimanganese decacarbonyl|dimanganese decacarbonyl]] {{chem2|Mn2(CO)10}}, an orange and volatile solid.  The air-stability of this Mn(0) compound (and its many derivatives) reflects the powerful electron-acceptor properties of carbon monoxide. Many alkene complexes and alkyne complexes are derived from {{chem2|Mn2(CO)10}}.{{citation needed|date=February 2023}}

In Mn(CH<sub>3</sub>)<sub>2</sub>(dmpe)<sub>2</sub>, Mn(II) is low spin, which contrasts with the high spin character of its precursor, MnBr<sub>2</sub>(dmpe)<sub>2</sub> (dmpe =  (CH<sub>3</sub>)<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>P(CH<sub>3</sub>)<sub>2</sub>).<ref>{{cite journal |doi=10.1021/ja00360a054|title=Hydrido, alkyl, and ethylene 1,2-bis(dimethylphosphino)ethane complexes of manganese and the crystal structures of MnBr2(dmpe)2, &#91;Mn(AlH4)(dmpe)2&#93;2 and MnMe2(dmpe)2 |year=1983 |last1=Girolami |first1=Gregory S. |last2=Wilkinson |first2=Geoffrey |last3=Thornton-Pett |first3=Mark |last4=Hursthouse |first4=Michael B. |journal=Journal of the American Chemical Society |volume=105 |issue=22 |pages=6752–6753 }}</ref> Polyalkyl and polyaryl derivatives of manganese often exist in higher oxidation states, reflecting the electron-releasing properties of alkyl and aryl ligands.  One example is [Mn(CH<sub>3</sub>)<sub>6</sub>]<sup>2-</sup>.{{citation needed|date=February 2023}}

==History==
The origin of the name manganese is complex. In ancient times, two black minerals were identified from the regions of the Magnetes (either Magnesia, located within modern Greece, or Magnesia ad Sipylum, located within modern Turkey).<ref name="LanguageHAt">{{cite web |last1=languagehat |title=MAGNET. |url=http://languagehat.com/magnet/ |website=languagehat.com |access-date=18 June 2020 |language=en |date=28 May 2005}}</ref> They were both called ''magnes'' from their place of origin, but were considered to differ in sex. The male ''magnes'' attracted iron, and was the iron ore now known as [[Physics:Lodestone|lodestone]] or [[Chemistry:Magnetite|magnetite]], and which probably gave us the term [[Physics:Magnet|magnet]]. The female ''magnes'' ore did not attract iron, but was used to decolorize glass. This female ''magnes'' was later called ''magnesia'', known now in modern times as [[Chemistry:Pyrolusite|pyrolusite]] or [[Chemistry:Manganese dioxide|manganese dioxide]].<ref>{{Cite book |last=Pliny the Elder |url=https://www.gutenberg.org/cache/epub/62704/pg62704-images.html |title=Natural History of Pliny. BOOK XXXVI. THE NATURAL HISTORY OF STONES. |chapter=Chapter 25—THE MAGNET: THREE REMEDIES |author-link=Pliny the Elder}}</ref> Neither this mineral nor elemental manganese is magnetic. In the 16th century, manganese dioxide was called ''manganesum'' (note the two Ns instead of one) by glassmakers, possibly as a corruption and concatenation of two words, since alchemists and glassmakers eventually had to differentiate a ''magnesia nigra'' (the black ore) from ''magnesia alba'' (a white ore, also from Magnesia, also useful in glassmaking). Michele Mercati called magnesia nigra ''manganesa'', and finally the metal isolated from it became known as ''manganese'' ({{Lang-de|Mangan}}). The name ''magnesia'' eventually was then used to refer only to the white magnesia alba (magnesium oxide), which provided the name [[Chemistry:Magnesium|magnesium]] for the free element when it was isolated much later.<ref>{{cite web|last=Calvert|first=J. B.|url=http://mysite.du.edu/~jcalvert/phys/chromang.htm|title=Chromium and Manganese|access-date=10 December 2022|date=24 January 2003|url-status=dead|archive-url=https://web.archive.org/web/20161231161307/http://mysite.du.edu/~jcalvert/phys/chromang.htm|archive-date=31 December 2016}}</ref>

[[File:Lascaux painting.jpg|thumb| left |alt=A drawing of a left-facing bull, in black, on a cave wall |Some of the cave paintings in Lascaux, {{wipe|France}}, use manganese-based pigments.<ref name="Lascaux">{{cite journal|doi=10.1088/0957-0233/14/9/310|title=Analysis of rock art painting and technology of Palaeolithic painters|date=2003|last=Chalmin|first=Emilie |author2=Menu, Michel |author3=Vignaud, Colette|journal=Measurement Science and Technology|volume=14|pages=1590–1597|issue=9|s2cid=250842390 }}</ref>]]

Manganese dioxide, which is abundant in nature, has long been used as a pigment. The cave paintings in Gargas that are 30,000 to 24,000 years old are made from the mineral form of MnO<sub>2</sub> pigments.<ref>{{cite journal|doi=10.1007/s00339-006-3510-7|title=Minerals discovered in paleolithic black pigments by transmission electron microscopy and micro-X-ray absorption near-edge structure|date=2006|last1=Chalmin|first1=E.|last2=Vignaud|first2=C. |last3=Salomon|first3=H.|last4=Farges|first4=F.|last5=Susini|first5=J. |last6= Menu|first6=M.|journal=Applied Physics A|volume=83 |pages=213–218|issue=12|bibcode=2006ApPhA..83..213C|hdl=2268/67458|s2cid=9221234|url=http://orbi.ulg.ac.be/bitstream/2268/67458/1/fulltext.pdf}}</ref>

Manganese compounds were used by Egyptian and Roman glassmakers, either to add to, or remove, color from glass.<ref>{{cite journal |doi=10.1126/science.133.3467.1824|date=1961|last=Sayre|first=E. V.|author2=Smith, R. W.|title=Compositional Categories of Ancient Glass |volume=133|issue=3467|pages=1824–1826|journal=Science|pmid=17818999|bibcode=1961Sci...133.1824S|s2cid=25198686}}</ref> Use as "glassmakers soap" continued through the [[History:Middle Ages|Middle Ages]] until modern times and is evident in 14th-century glass from Venice.<ref name="ItGlass" />

[[File:Gahn Johan Gottlieb.jpg|thumb|upright|Credit for first isolating manganese is usually given to Johan Gottlieb Gahn.]]

Because it was used in glassmaking, manganese dioxide was available for experiments by alchemists, the first chemists. [[Biography:Ignatius Gottfried Kaim|Ignatius Gottfried Kaim]] (1770) and Johann Glauber (17th century) discovered that manganese dioxide could be converted to [[Chemistry:Permanganate|permanganate]], a useful laboratory reagent.<ref>{{cite journal|journal=Centaurus|volume=19|issue=4|title=The Discovery of an Element|first=E.|last=Rancke-Madsen|doi=10.1111/j.1600-0498.1975.tb00329.x|pages=299–313|date=1975|bibcode=1975Cent...19..299R}}</ref> Kaim also may have reduced manganese dioxide to isolate the metal, but that is uncertain.<ref name=Miskowiec>{{cite journal |last1=Miśkowiec |first1=Paweł |date=2022 |title=Name game: the naming history of the chemical elements—part 1—from antiquity till the end of 18th century |journal=Foundations of Chemistry |volume= 25|issue= |pages= 29–51|doi=10.1007/s10698-022-09448-5 |doi-access=free }}</ref> By the mid-18th century, the Swedish chemist [[Biography:Carl Wilhelm Scheele|Carl Wilhelm Scheele]] used manganese dioxide to produce [[Chemistry:Chlorine|chlorine]]. First, [[Chemistry:Hydrochloric acid|hydrochloric acid]], or a mixture of dilute [[Chemistry:Sulfuric acid|sulfuric acid]] and [[Chemistry:Sodium chloride|sodium chloride]] was made to react with manganese dioxide, and later hydrochloric acid from the [[Chemistry:Leblanc process|Leblanc process]] was used and the manganese dioxide was recycled by the [[Chemistry:Weldon process|Weldon process]]. The production of chlorine and [[Chemistry:Hypochlorite|hypochlorite]] [[Chemistry:Bleach|bleach]]ing agents was a large consumer of manganese ores.{{citation needed|date=February 2023}}

Scheele and others were aware that pyrolusite (mineral form of manganese dioxide) contained a new element. [[Biography:Johan Gottlieb Gahn|Johan Gottlieb Gahn]] isolated an impure sample of manganese metal in 1774, which he did by reducing the dioxide with [[Chemistry:Carbon|carbon]].{{citation needed|date=February 2023}}

The manganese content of some iron ores used in Greece led to speculations that steel produced from that ore contains additional manganese, making the Spartan steel exceptionally hard.<ref>{{cite journal|doi=10.1002/ajim.20524|date=2007|title=From lead to manganese through mercury: mythology, science, and lessons for prevention|volume=50|issue=11|pages=779–787 |journal=American Journal of Industrial Medicine|pmid=17918211|last1=Alessio|first1=L.|last2=Campagna|first2=M.|last3=Lucchini|first3=R.}}</ref> Around the beginning of the 19th century, manganese was used in steelmaking and several patents were granted. In 1816, it was documented that iron alloyed with manganese was harder but not more brittle. In 1837, British academic James Couper noted an association between miners' heavy exposure to manganese and a form of [[Medicine:Parkinson's disease|Parkinson's disease]].<ref name="Couper 1837 41–42" /> In 1912, United States patents were granted for protecting firearms against rust and corrosion with manganese phosphate electrochemical conversion coatings, and the process has seen widespread use ever since.<ref>{{cite book|title=Production of Manganese Ferroalloys|publisher=Tapir Academic Press |date=2007|isbn=978-82-519-2191-6|chapter=History of omanganese|pages=11–12|author=Olsen, Sverre E.|author2=Tangstad, Merete |author3=Lindstad, Tor}}</ref>

The invention of the Leclanché cell in 1866 and the subsequent improvement of batteries containing manganese dioxide as cathodic [[Chemistry:Depolarizer|depolarizer]] increased the demand for manganese dioxide. Until the development of batteries with [[Chemistry:Nickel–cadmium battery|nickel–cadmium]] and lithium, most batteries contained manganese. The zinc–carbon battery and the [[Physics:Alkaline battery|alkaline battery]] normally use industrially produced manganese dioxide because naturally occurring manganese dioxide contains impurities. In the 20th century, manganese dioxide was widely used as the cathodic for commercial disposable dry batteries of both the standard (zinc–carbon) and alkaline types.<ref name="ChiuZMnO2">{{cite journal|doi=10.1002/ciuz.19800140502|title=Moderne Verfahren der Großchemie: Braunstein |date=1980|last=Preisler|first=Eberhard|journal=Chemie in unserer Zeit|language=de|volume=14|pages=137–148|issue=5}}</ref>

==Occurrence==
Manganese comprises about 1000&nbsp;[[Parts per million|ppm]] (0.1%) of the [[Earth:Earth's crust|Earth's crust]], the 12th most abundant of the crust's elements.<ref name="Emsley2001">{{cite book|title=Nature's Building Blocks: An A-Z Guide to the Elements|last=Emsley|first=John|publisher=Oxford University Press|date=2001|location=Oxford, UK|isbn=978-0-19-850340-8|chapter=Manganese|pages=[https://archive.org/details/naturesbuildingb0000emsl/page/249 249–253]|chapter-url=https://books.google.com/books?id=j-Xu07p3cKwC|url=https://archive.org/details/naturesbuildingb0000emsl/page/249}}</ref> Soil contains 7–9000&nbsp;ppm of manganese with an average of 440&nbsp;ppm.<ref name="Emsley2001" /> The atmosphere contains 0.01&nbsp;μg/m<sup>3</sup>.<ref name="Emsley2001" /> Manganese occurs principally as [[Chemistry:Pyrolusite|pyrolusite]] (MnO<sub>2</sub>), [[Chemistry:Braunite|braunite]] (Mn<sup>2+</sup>Mn<sup>3+</sup><sub>6</sub>)SiO<sub>12</sub>),<ref>{{cite journal|pages=65–71 |journal=Contributions to Mineralogy and Petrology|title=Geochemistry of braunite and associated phases in metamorphosed non-calcareous manganese ores of India|first=P. K.|last=Bhattacharyya|author2=Dasgupta, Somnath |author3=Fukuoka, M. |author4=Roy Supriya |doi=10.1007/BF00371403|date=1984|volume=87|issue=1|bibcode=1984CoMP...87...65B|s2cid=129495326}}</ref> [[Chemistry:Psilomelane|psilomelane]] {{chem2|(Ba,H2O)2Mn5O10}}, and to a lesser extent as [[Chemistry:Rhodochrosite|rhodochrosite]] ([[Chemistry:Manganese(II) carbonate|MnCO<sub>3</sub>]]).

{|class="wikitable"
|[[File:ManganeseOreUSGOV.jpg|center|120px]]
|[[File:Mineraly.sk - psilomelan.jpg|center|140px]]
|[[File:Spiegeleisen.jpg|center|150px]]
|[[File:Dendrites01.jpg|center|130px]]
|[[File:The Searchlight Rhodochrosite Crystal.jpg|center|140px]]
|-
|Manganese ore
|Psilomelane (manganese ore)
|[[Chemistry:Spiegeleisen|Spiegeleisen]] is an iron alloy with a manganese content of approximately 15%.
|Manganese oxide dendrites on limestone from Solnhofen, Germany – a kind of pseudofossil. Scale is in mm
|Mineral [[Chemistry:Rhodochrosite|rhodochrosite]] ([[Chemistry:Manganese(II) carbonate|manganese(II) carbonate]])
|}
[[File:World Manganese Production 2006.svg|thumb|upright=1.6|Percentage of manganese output in 2006 by countries<ref name="USGSMCS2009">USGS Mineral Commodity Summaries 2009</ref>]]

The most important manganese ore is pyrolusite (MnO<sub>2</sub>). Other economically important manganese ores usually show a close spatial relation to the iron ores, such as [[Chemistry:Sphalerite|sphalerite]].<ref name="Holl" /><ref>{{Cite journal|last1=Cook|first1=Nigel J.|last2=Ciobanu|first2=Cristiana L.|last3=Pring|first3=Allan|last4=Skinner|first4=William|last5=Shimizu|first5=Masaaki|last6=Danyushevsky|first6=Leonid|last7=Saini-Eidukat|first7=Bernhardt|last8=Melcher|first8=Frank|date=2009|title=Trace and minor elements in sphalerite: A LA-ICPMS study|url=https://linkinghub.elsevier.com/retrieve/pii/S0016703709003263|journal=Geochimica et Cosmochimica Acta|language=en|volume=73|issue=16|pages=4761–4791|doi=10.1016/j.gca.2009.05.045|bibcode=2009GeCoA..73.4761C}}</ref> Land-based resources are large but irregularly distributed. About 80% of the known world manganese resources are in South Africa; other important manganese deposits are in Ukraine, Australia, India, China, Gabon and Brazil.<ref name="USGSMCS2009" /> According to 1978 estimate, the ocean floor has 500&nbsp;billion tons of [[Earth:Manganese nodule|manganese nodule]]s.<ref>{{cite journal|doi=10.1016/j.micron.2008.10.005|pages=350–358|date=2009|title=Manganese/polymetallic nodules: micro-structural characterization of exolithobiontic- and endolithobiontic microbial biofilms by scanning electron microscopy|volume=40 |issue=3|pmid=19027306|journal=Micron |author1=Wang, X|author2=Schröder, HC|author3=Wiens, M|author4=Schlossmacher, U|author5=Müller, WEG}}</ref> Attempts to find economically viable methods of harvesting manganese nodules were abandoned in the 1970s.<ref>{{cite book |title=Manganese Nodules: Dimensions and Perspectives|journal=Marine Geology|volume=41|issue=3–4|pages=343|publisher=Springer|date=1978|isbn=978-90-277-0500-6|author=United Nations|bibcode=1981MGeol..41..343C|doi=10.1016/0025-3227(81)90092-X|oclc=4515098|series=Natural Resources Forum Library}}</ref>

In South Africa, most identified deposits are located near Hotazel in the Northern Cape Province, (Kalahari manganese fields), with a 2011 estimate of 15&nbsp;billion tons. In 2011 South Africa produced 3.4&nbsp;million tons, topping all other nations.<ref name="Mbendi">{{cite web |url=http://www.mbendi.com/indy/ming/mang/af/sa/p0005.htm |title=Manganese Mining in South Africa – Overview |publisher=MBendi Information Services |access-date=10 December 2022 |url-status=dead |archive-url=https://web.archive.org/web/20160205194737/http://www.mbendi.com/indy/ming/mang/af/sa/p0005.htm |archive-date=5 February 2016}}</ref>

Manganese is mainly mined in South Africa, Australia, China, Gabon, Brazil, India, Kazakhstan, Ghana, Ukraine and Malaysia.<ref>{{Cite journal|doi = 10.1007/s11837-018-2769-4|title = Review of Manganese Processing for Production of TRIP/TWIP Steels, Part 1: Current Practice and Processing Fundamentals|journal = JOM |volume = 70|issue = 5|pages = 680–690|year = 2018|last1 = Elliott|first1 = R|last2 = Coley|first2 = K|last3 = Mostaghel|first3 = S|last4 = Barati|first4 = M|bibcode = 2018JOM....70e.680E|s2cid = 139950857}}</ref>

== Production ==
For the production of [[Chemistry:Ferromanganese|ferromanganese]], the manganese ore is mixed with iron ore and carbon, and then reduced either in a blast furnace or in an electric arc furnace.<ref name="IndMin">{{cite book|title=Industrial Minerals & Rocks: Commodities, Markets, and Uses |edition=7th|publisher=SME|date=2006|isbn=978-0-87335-233-8|chapter=Manganese|first=L. A.|last=Corathers |author2=Machamer, J. F. |chapter-url=https://books.google.com/books?id=zNicdkuulE4C&pg=PA631|pages=631–636}}</ref> The resulting ferromanganese has a manganese content of 30–80%.<ref name="Holl" /> Pure manganese used for the production of iron-free alloys is produced by [[Engineering:Leaching (metallurgy)|leaching]] manganese ore with [[Chemistry:Sulfuric acid|sulfuric acid]] and a subsequent [[Physics:Electrowinning|electrowinning]] process.<ref name="hydrometI">{{cite journal|doi=10.1016/j.hydromet.2007.08.010 |title=Manganese metallurgy review. Part I: Leaching of ores/secondary materials and recovery of electrolytic/chemical manganese dioxide|date=2007|last=Zhang|first=Wensheng|author2=Cheng, Chu Yong|journal=Hydrometallurgy|volume=89 |pages=137–159|issue=3–4|bibcode=2007HydMe..89..137Z }}</ref>

[[File:Manganese Process Flow Diagram.jpg|thumb|upright=1.75|alt=Contains reactions and temperatures, as well as showing advanced processes such as the heat exchanger and milling process.|Process flow diagram for a manganese refining circuit]]
A more progressive extraction process involves directly reducing (a low grade) manganese ore by [[Engineering:Heap leaching|heap leaching]]. This is done by [[Percolation|percolating]] natural gas through the bottom of the heap; the natural gas provides the heat (needs to be at least 850&nbsp;°C) and the reducing agent (carbon monoxide). This reduces all of the manganese ore to manganese oxide (MnO), which is a leachable form. The ore then travels through a grinding circuit to reduce the particle size of the ore to between 150 and 250 μm, increasing the surface area to aid leaching. The ore is then added to a leach tank of sulfuric acid and [[Chemistry:Iron(II)|ferrous iron]] (Fe<sup>2+</sup>) in a 1.6:1 ratio. The iron reacts with the [[Chemistry:Manganese dioxide|manganese dioxide]] (MnO<sub>2</sub>) to form iron hydroxide (FeO(OH)) and elemental manganese (Mn).{{citation needed|date=February 2023}}

This process yields approximately 92% recovery of the manganese. For further purification, the manganese can then be sent to an [[Physics:Electrowinning|electrowinning]] facility.<ref name="ManganeseRecovery">{{cite web|url=http://www.americanmanganeseinc.com/wp-content/uploads/2011/08/American-Manganese-Phase-II-August-19-2010-Final-Report-Internet-Version-V2.pdf|title=The Recovery of Manganese from low grade resources: bench scale metallurgical test program completed|date=2010|author=Chow, Norman|author2=Nacu, Anca|author3=Warkentin, Doug|author4=Aksenov, Igor|author5=Teh, Hoe|name-list-style=amp|publisher=Kemetco Research Inc.|url-status=dead|archive-url=https://web.archive.org/web/20120202065633/http://www.americanmanganeseinc.com/wp-content/uploads/2011/08/American-Manganese-Phase-II-August-19-2010-Final-Report-Internet-Version-V2.pdf|archive-date=2 February 2012}}</ref>

In 1972 the CIA's [[Unsolved:Project Azorian|Project Azorian]], through billionaire [[Biography:Howard Hughes|Howard Hughes]], commissioned the ship ''Hughes Glomar Explorer'' with the cover story of harvesting manganese nodules from the sea floor.<ref>{{Cite news|url=https://www.bbc.com/news/science-environment-42994812|title=The CIA secret on the ocean floor|date=19 February 2018|work=BBC News|access-date=3 May 2018|language=en-GB}}</ref> That triggered a rush of activity to collect manganese nodules, which was not actually practical. The real mission of ''Hughes Glomar Explorer'' was to raise a sunken {{wipe|Union of Soviet Socialist Republics}} submarine, the K-129, with the goal of retrieving Soviet code books.<ref name="azorian">{{cite web |url=http://www2.gwu.edu/~nsarchiv/nukevault/ebb305/index.htm |title=Project Azorian: The CIA's Declassified History of the Glomar Explorer |publisher=National Security Archive at George Washington University |date=12 February 2010 |access-date=18 September 2013}}</ref>

An abundant resource of manganese in the form of manganese nodules found on the ocean floor.<ref>{{cite book |last1=Hein |first1=James R. |title=Encyclopedia of Marine Geosciences - Manganese Nodules |date=January 2016 |publisher=Springer |pages=408–412 |url=https://www.researchgate.net/publication/306107551 |access-date=2 February 2021}}</ref><ref>{{cite journal |last1=Hoseinpour |first1=Vahid |last2=Ghaemi |first2=Nasser |title=Green synthesis of manganese nanoparticles: Applications and future perspective–A review |journal=Journal of Photochemistry and Photobiology B: Biology |date=1 December 2018 |volume=189 |pages=234–243 |doi=10.1016/j.jphotobiol.2018.10.022 |pmid=30412855 |s2cid=53248245 |url=https://www.sciencedirect.com/science/article/abs/pii/S101113441830959X |access-date=2 February 2021}}</ref> These nodules, which are composed of 29% manganese,<ref>{{cite web |last1=International Seabed Authority |title=Polymetallic Nodules |url=https://isa.org.jm/files/files/documents/eng7.pdf |website=isa.org |publisher=International Seabed Authority |access-date=2 February 2021}}</ref> are located along the [[Earth:Seabed|ocean floor]] and the potential impact of mining these nodules is being researched. Physical, chemical, and biological environmental impacts can occur due to this nodule mining disturbing the seafloor and causing sediment plumes to form. This suspension includes metals and inorganic nutrients, which can lead to contamination of the near-bottom waters from dissolved toxic compounds. Manganese nodules are also the grazing grounds, living space, and protection for endo- and epifaunal systems. When theses nodules are removed, these systems are directly affected. Overall, this can cause species to leave the area or completely die off.<ref>{{Cite journal|last1=Oebius|first1=Horst U|last2=Becker|first2=Hermann J|last3=Rolinski|first3=Susanne|last4=Jankowski|first4=Jacek A|date=January 2001|title=Parametrization and evaluation of marine environmental impacts produced by deep-sea manganese nodule mining|url=http://dx.doi.org/10.1016/s0967-0645(01)00052-2|journal=Deep Sea Research Part II: Topical Studies in Oceanography|volume=48|issue=17–18|pages=3453–3467|doi=10.1016/s0967-0645(01)00052-2|bibcode=2001DSRII..48.3453O|issn=0967-0645}}</ref> Prior to the commencement of the mining itself, research is being conducted by {{wipe|United Nations}} affiliated bodies and state-sponsored companies in an attempt to fully understand environmental impacts in the hopes of mitigating these impacts.<ref>{{cite journal |last1=Thompson |first1=Kirsten F. |last2=Miller |first2=Kathryn A. |last3=Currie |first3=Duncan |last4=Johnston |first4=Paul |last5=Santillo |first5=David |title=Seabed Mining and Approaches to Governance of the Deep Seabed |journal=Frontiers in Marine Science |date=2018 |volume=5 |doi=10.3389/fmars.2018.00480 |s2cid=54465407 |doi-access=free |hdl=10871/130176 |hdl-access=free }}</ref>

===Oceanic environment===
Many trace elements in the ocean come from metal-rich hydrothermal particles from hydrothermal vents.<ref name="Ray-2017">{{Cite journal|last1=Ray|first1=Durbar|last2=Babu|first2=E. V. S. S. K.|last3=Surya Prakash|first3=L.|date=1 January 2017|title=Nature of Suspended Particles in Hydrothermal Plume at 3°40'N Carlsberg Ridge:A Comparison with Deep Oceanic Suspended Matter|journal=Current Science|volume=112|issue=1|pages=139|doi=10.18520/cs/v112/i01/139-146 |issn=0011-3891|doi-access=free}}</ref> Dissolved manganese (dMn) is found throughout the world's oceans, 90% of which originates from hydrothermal vents.<ref name="Hernroth-2020">{{Cite journal|last1=Hernroth|first1=Bodil|last2=Tassidis|first2=Helena|last3=Baden|first3=Susanne P.|date=March 2020|title=Immunosuppression of aquatic organisms exposed to elevated levels of manganese: From global to molecular perspective|url=http://dx.doi.org/10.1016/j.dci.2019.103536|journal=Developmental & Comparative Immunology|volume=104|pages=103536|doi=10.1016/j.dci.2019.103536|pmid=31705914|s2cid=207935992|issn=0145-305X}}</ref> Particulate Mn develops in buoyant plumes over an active vent source, while the dMn behaves conservatively.<ref name="Ray-2017" /> Mn concentrations vary between the water columns of the ocean. At the surface, dMn is elevated due to input from external sources such as rivers, dust, and shelf sediments. Coastal sediments normally have lower Mn concentrations, but can increase due to anthropogenic discharges from industries such as mining and steel manufacturing, which enter the ocean from river inputs. Surface dMn concentrations can also be elevated biologically through photosynthesis and physically from coastal upwelling and wind-driven surface currents. Internal cycling such as photo-reduction from UV radiation can also elevate levels by speeding up the dissolution of Mn-oxides and oxidative scavenging, preventing Mn from sinking to deeper waters.<ref name="Sim-2019">{{Cite journal|last1=Sim|first1=Nari|last2=Orians|first2=Kristin J.|date=October 2019|title=Annual variability of dissolved manganese in Northeast Pacific along Line-P: 2010–2013|url=http://dx.doi.org/10.1016/j.marchem.2019.103702|journal=Marine Chemistry|volume=216|pages=103702|doi=10.1016/j.marchem.2019.103702|bibcode=2019MarCh.21603702S |s2cid=203151735|issn=0304-4203}}</ref> Elevated levels at mid-depths can occur near mid-ocean ridges and hydrothermal vents. The hydrothermal vents release dMn enriched fluid into the water. The dMn can then travel up to 4,000&nbsp;km due to the microbial capsules present, preventing exchange with particles, lowing the sinking rates. Dissolved Mn concentrations are even higher when oxygen levels are low. Overall, dMn concentrations are normally higher in coastal regions and decrease when moving offshore.<ref name="Sim-2019" />

=== Soils ===
Manganese occurs in soils in three oxidation states: the divalent cation, Mn<sup>2+</sup> and as brownish-black oxides and hydroxides containing Mn (III,IV), such as MnOOH and MnO<sub>2</sub>. Soil pH and oxidation-reduction conditions affect which of these three forms of Mn is dominant in a given soil. At pH values less than 6 or under anaerobic conditions, Mn(II) dominates, while under more alkaline and aerobic conditions, Mn(III,IV) oxides and hydroxides predominate. These effects of soil acidity and aeration state on the form of Mn can be modified or controlled by microbial activity. Microbial respiration can cause both the oxidation of Mn<sup>2+</sup> to the oxides, and it can cause reduction of the oxides to the divalent cation.<ref>{{Cite book|last1=Bartlett|first1=Richmond|title=Chemical Processes in Soils|last2=Ross|first2=Donald|publisher=Soil Science Society of America|year=2005|editor-last=Tabatabai|editor-first=M.A.|series=SSSA Book Series, no. 8|location=Madison, Wisconsin|pages=461–487|chapter=Chemistry of Redox Processes in Soils|lccn=2005924447|editor-last2=Sparks|editor-first2=D.L.}}</ref>

The Mn(III,IV) oxides exist as brownish-black stains and small nodules on sand, silt, and clay particles. These surface coatings on other soil particles have high surface area and carry negative charge. The charged sites can adsorb and retain various cations, especially heavy metals (e.g., Cr<sup>3+</sup>, Cu<sup>2+</sup>, Zn<sup>2+</sup>, and Pb<sup>2+</sup>). In addition, the oxides can adsorb organic acids and other compounds. The adsorption of the metals and organic compounds can then cause them to be oxidized while the Mn(III,IV) oxides are reduced to Mn<sup>2+</sup> (e.g., Cr<sup>3+</sup> to Cr(VI) and colorless [[Chemistry:Hydroquinone|hydroquinone]] to tea-colored [[Chemistry:Quinone|quinone]] polymers).<ref>{{Cite book|last1=Dixon|first1=Joe B.|title=Soil Mineralogy with Environmental Applications|last2=White|first2=G. Norman|publisher=Soil Science Society of America|year=2002|editor-last=Dixon|editor-first=J.B.|series=SSSA Book Series no. 7|location=Madison, Wisconsin|pages=367–386|chapter=Manganese Oxides|lccn=2002100258|editor-last2=Schulze|editor-first2=D.G.}}</ref>

==Applications==
Manganese has no satisfactory substitute in its major applications in metallurgy.<ref name="USGSMCS2009" /> In minor applications (e.g., manganese phosphating), [[Chemistry:Zinc|zinc]] and sometimes [[Chemistry:Vanadium|vanadium]] are viable substitutes.

===Steel===
[[File:M1917helmet.jpg|thumb|U.S. M1917 [[Engineering:Combat helmet|combat helmet]], a variant of Brodie helmet, made from Hadfield steel manganese alloy]]

Manganese is essential to iron and [[Engineering:Steelmaking|steel production]] by virtue of its [[Chemistry:Sulfur|sulfur]]-fixing, [[Engineering:Deoxidized steel|deoxidizing]], and alloying properties, as first recognized by the British metallurgist Robert Forester Mushet (1811–1891) who, in 1856, introduced the element, in the form of [[Chemistry:Spiegeleisen|Spiegeleisen]], into steel for the specific purpose of removing excess dissolved oxygen, sulfur, and phosphorus in order to improve its malleability. [[Engineering:Steelmaking|Steelmaking]],<ref>{{cite book|isbn=978-0-87170-858-8|pages=56–57|first=John D. |last=Verhoeven |date=2007 |publisher=ASM International |location=Materials Park, Ohio |title=Steel metallurgy for the non-metallurgist}}</ref> including its ironmaking component, has accounted for most manganese demand, presently in the range of 85% to 90% of the total demand.<ref name="hydrometI" /> Manganese is a key component of low-cost [[Chemistry:Stainless steel|stainless steel]].<ref name="MangUSGS2006">Manganese USGS 2006</ref><ref>{{cite journal |doi=10.1007/BF02648339 |title=Mechanism of work hardening in Hadfield manganese steel |date=1981 |last1=Dastur|first1=Y. N. |journal=Metallurgical Transactions A|volume=12|pages=749–759|last2=Leslie|first2=W. C.|issue=5|bibcode=1981MTA....12..749D|s2cid=136550117}}</ref> Often ferromanganese (usually about 80% manganese) is the intermediate in modern processes.

Small amounts of manganese improve the workability of steel at high temperatures by forming a high-melting sulfide and preventing the formation of a liquid [[Chemistry:Iron sulfide|iron sulfide]] at the grain boundaries. If the manganese content reaches 4%, the embrittlement of the steel becomes a dominant feature. The embrittlement decreases at higher manganese concentrations and reaches an acceptable level at 8%. Steel containing 8 to 15% of manganese has a high [[Physics:Tensile strength|tensile strength]] of up to 863&nbsp;MPa.<ref>{{cite book|isbn=978-1-4086-2616-0 |pages=351–352|title=Iron and Steel|first=John Henry |last=Stansbie|publisher=Read Books|url=https://books.google.com/books?id=FyogLqUxW1cC&pg=PA351 |date=2007}}</ref><ref>{{cite book|isbn=978-0-07-136076-0|pages=585–587|last=Brady|first=George S.|author2=Clauser, Henry R. |author3=Vaccari. John A. |date=2002|publisher=McGraw-Hill|location=New York, NY|title=Materials Handbook: an encyclopedia for managers, technical professionals, purchasing and production managers, technicians, and supervisors|url=https://books.google.com/books?id=vIhvSQLhhMEC&pg=PA585}}</ref> Steel with 12% manganese was discovered in 1882 by Robert Hadfield and is still known as [[Chemistry:Mangalloy|Hadfield steel (mangalloy)]]. It was used for British military steel helmets and later by the U.S. military.<ref>{{cite journal|title=Sir Robert Abbott Hadfield F.R.S. (1858–1940), and the Discovery of Manganese Steel Geoffrey Tweedale|journal=Notes and Records of the Royal Society of London|volume=40|issue=1 |date=1985|pages=63–74|doi=10.1098/rsnr.1985.0004|first=Geoffrey|last=Tweedale|jstor=531536|s2cid=73176861 |doi-access=}}</ref>

===Aluminium alloys===
{{Main|Chemistry:Aluminium alloy}}
Manganese is used in production of alloys with aluminium. Aluminium with roughly 1.5% manganese has increased resistance to corrosion through grains that absorb impurities which would lead to [[Chemistry:Galvanic corrosion|galvanic corrosion]].<ref>{{cite web |url=http://www.suppliersonline.com/propertypages/2024.asp|title=Chemical properties of 2024 aluminum allow|access-date=30 April 2009 |publisher=Metal Suppliers Online, LLC.}}</ref> The corrosion-resistant [[Chemistry:Aluminium alloy|aluminium alloy]]s 3004 and 3104 (0.8 to 1.5% manganese) are used for most beverage cans.<ref name="Al3004">{{cite book |title=Introduction to aluminum alloys and tempers|first=John Gilbert |last=Kaufman|publisher=ASM International|date=2000|isbn=978-0-87170-689-8|chapter=Applications for Aluminium Alloys and Tempers |pages=93–94|chapter-url=https://books.google.com/books?id=idmZIDcwCykC&pg=PA93}}</ref> Before 2000, more than 1.6&nbsp;million [[Tonne|tonne]]s of those alloys were used; at 1% manganese, this consumed 16,000 tonnes of manganese.{{failed verification|date=September 2018}}<ref name="Al3004" />

====Batteries====
Manganese(IV) oxide was used in the original type of dry cell [[Physics:Battery (electricity)|battery]] as an electron acceptor from zinc, and is the blackish material in carbon–zinc type flashlight cells. The manganese dioxide is reduced to the manganese oxide-hydroxide MnO(OH) during discharging, preventing the formation of hydrogen at the anode of the battery.<ref name="BattHist" />

:MnO<sub>2</sub> + H<sub>2</sub>O + e<sup>−</sup> → MnO(OH) + {{chem|OH|-}}

The same material also functions in newer [[Physics:Alkaline battery|alkaline batteries]] (usually battery cells), which use the same basic reaction, but a different electrolyte mixture. In 2002, more than 230,000&nbsp;tons of manganese dioxide was used for this purpose.<ref name="ChiuZMnO2" /><ref name="BattHist">{{cite journal|doi=10.1016/S0167-2738(00)00722-0|title=Batteries fifty years of materials development|date=2000|last=Dell|first=R. M.|journal=Solid State Ionics|volume=134|issue=1–2|pages=139–158}}</ref>

[[File:1945-P-Jefferson-War-Nickel-Reverse.JPG|upright|thumb|World-War-II-era 5-cent coin (1942-5 identified by mint mark P, D or S above dome) made from a 56% copper-35% silver-9% manganese alloy]]

====Resistors====
Copper alloys of manganese, such as [[Chemistry:Manganin|Manganin]], are commonly found in metal element shunt resistors used for measuring relatively large amounts of current. These alloys have very low [[Physics:Temperature coefficient of resistance|temperature coefficient of resistance]] and are resistant to sulfur. This makes the alloys particularly useful in harsh automotive and industrial environments.<ref name="ShuntDatasheet">{{cite web |title=WSK1216 |url=https://www.vishay.com/docs/30189/wsk1216.pdf |website=vishay |publisher=Vishay Intertechnology |access-date=30 April 2022}}</ref>

====Fertilizers and feed additive====
[[Chemistry:Manganese(II) oxide|Manganese oxide]] and sulfate are components of fertilizers.  In the year 2000, an estimated 20,000 tons of these compounds were used in fertilizers in the US alone.  A comparable amount of Mn compounds was also used in animal feeds. <ref>{{cite book |doi=10.1002/14356007.a16_123 |chapter=Manganese Compounds |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2000 |last1=Reidies |first1=Arno H. |isbn=9783527303854 }}</ref>

====Niche====
[[Chemistry:Methylcyclopentadienyl manganese tricarbonyl|Methylcyclopentadienyl manganese tricarbonyl]] is an additive in some unleaded gasoline to boost octane rating and reduce [[Engineering:Engine knocking|engine knocking]]. <ref>{{cite web |title=EPA Comments on the Gasoline Additive MMT |url=https://www.epa.gov/gasoline-standards/epa-comments-gasoline-additive-mmt |website=epa.gov |date=5 October 2015 |publisher=EPA |access-date=25 June 2023}}</ref>

Manganese(IV) oxide (manganese dioxide, MnO<sub>2</sub>) is used as a reagent in [[Chemistry:Organic chemistry|organic chemistry]] for the oxidation of benzylic [[Chemistry:Alcohol|alcohol]]s (where the hydroxyl group is adjacent to an aromatic ring). Manganese dioxide has been used since antiquity to oxidize and neutralize the greenish tinge in glass from trace amounts of iron contamination.<ref name="ItGlass">{{cite journal |doi=10.1007/s11837-998-0024-0|title=Glassmaking in renaissance Italy: The innovation of venetian cristallo|date=1998|last=Mccray |first=W. Patrick|journal=JOM|volume=50|pages=14–19|issue=5|bibcode=1998JOM....50e..14M|s2cid=111314824}}</ref> MnO<sub>2</sub> is also used in the manufacture of oxygen and chlorine and in drying black paints. In some preparations, it is a brown pigment for [[Engineering:Paint|paint]] and is a constituent of natural [[Umber|umber]].<ref name=straightouttathetheumberwikiarticle>{{cite book |title=Shorter Oxford English Dictionary |url=https://archive.org/details/shorteroxfordeng00will_0 |publisher=Oxford University Press |year=2002 |isbn=978-0-19-860457-0 |quote=A red brown earth containing iron and manganese oxides and darker than ochre and sienna, used to make various pigments. |edition=5th}}</ref>

[[Chemistry:Tetravalence|Tetravalent]] manganese is used as an [[Physics:Activator (phosphor)|activator]] in red-emitting [[Physics:Phosphor|phosphor]]s. While many compounds are known which show [[Physics:Luminescence|luminescence]],<ref>{{cite journal|journal=RSC Advances |date=2016|volume=6|issue=89|pages=86285–86296|first=Daquin|last=Chen|author2=Zhou, Yang |author3=Zhong, Jiasong |title=A review on Mn<sup>4+</sup> activators in solids for warm white light-emitting diodes|doi=10.1039/C6RA19584A|bibcode=2016RSCAd...686285C}}</ref> the majority are not used in commercial application due to low efficiency or deep red emission.<ref>{{cite journal|journal=Journal of Luminescence |date=2016|volume=177|pages=354–360|first=Florian|last=Baur|author2=Jüstel, Thomas|title=Dependence of the optical properties of Mn<sup>4+</sup> activated A<sub>2</sub>Ge<sub>4</sub>O<sub>9</sub> (A=K,Rb) on temperature and chemical environment|doi=10.1016/j.jlumin.2016.04.046|bibcode=2016JLum..177..354B}}</ref><ref>{{Cite journal|last1=Jansen|first1=T.|last2=Gorobez|first2=J.|last3=Kirm|first3=M.|last4=Brik|first4=M. G.|last5=Vielhauer|first5=S.|last6=Oja|first6=M.|last7=Khaidukov|first7=N. M.|last8=Makhov|first8=V. N.|last9=Jüstel|first9=T.|date=1 January 2018|title=Narrow Band Deep Red Photoluminescence of Y<sub>2</sub>Mg<sub>3</sub>Ge<sub>3</sub>O<sub>12</sub>:Mn<sup>4+</sup>,Li<sup>+</sup> Inverse Garnet for High Power Phosphor Converted LEDs|journal=ECS Journal of Solid State Science and Technology|volume=7|issue=1|pages=R3086–R3092|doi=10.1149/2.0121801jss|s2cid=103724310 |doi-access=free}}</ref> However, several Mn<sup>4+</sup> activated fluorides were reported as potential red-emitting phosphors for warm-white LEDs.<ref>{{Cite journal|last1=Jansen|first1=Thomas|last2=Baur|first2=Florian|last3=Jüstel|first3=Thomas|title=Red emitting K<sub>2</sub>NbF<sub>7</sub>:Mn<sup>4+</sup> and K<sub>2</sub>TaF<sub>7</sub>:Mn<sup>4+</sup> for warm-white LED applications|journal=Journal of Luminescence|volume=192|pages=644–652|doi=10.1016/j.jlumin.2017.07.061|year=2017|bibcode=2017JLum..192..644J}}</ref><ref>{{Cite journal|last1=Zhou|first1=Zhi|last2=Zhou|first2=Nan|last3=Xia|first3=Mao|last4=Yokoyama|first4=Meiso|last5=Hintzen|first5=H. T. (Bert)|date=6 October 2016|title=Research progress and application prospects of transition metal Mn<sup>4+</sup>-activated luminescent materials|journal=Journal of Materials Chemistry C|volume=4|issue=39|pages=9143–9161|doi=10.1039/c6tc02496c}}</ref> But to this day, only K<sub>2</sub>SiF<sub>6</sub>:Mn<sup>4+</sup> is commercially available for use in warm-white [[Engineering:LED|LED]]s.<ref>{{cite web|url=https://energy.gov/sites/prod/files/2015/02/f19/setlur_emitters_2015.pdf|title=TriGain LED phosphor system using red Mn<sup>4+</sup>-doped complex fluorides|publisher=GE Global Research |access-date=10 December 2022}}</ref>

The metal is occasionally used in coins; until 2000, the only United States coin to use manganese was the "wartime" nickel from 1942 to 1945.<ref>{{cite journal|journal=Western Journal of Medicine |date=2001|volume=175|issue=2|pages=112–114|first=Raymond T.|last=Kuwahara|author2=Skinner III, Robert B. |author3=Skinner Jr., Robert B. |title=Nickel coinage in the United States|doi=10.1136/ewjm.175.2.112|pmid=11483555|pmc=1071501}}</ref> An alloy of 75% copper and 25% nickel was traditionally used for the production of nickel coins. However, because of shortage of nickel metal during the war, it was substituted by more available silver and manganese, thus resulting in an alloy of 56% copper, 35% silver and 9% manganese. Since 2000, dollar coins, for example the Sacagawea dollar and the Presidential $1 coins, are made from a brass containing 7% of manganese with a pure copper core.<ref>{{cite web|url=http://www.usmint.gov/mint_programs/golden_dollar_coin/index.cfm?action=sacDesign|title=Design of the Sacagawea dollar|publisher=United States Mint |access-date=4 May 2009}}</ref> In both cases of nickel and dollar, the use of manganese in the coin was to duplicate the electromagnetic properties of a previous identically sized and valued coin in the mechanisms of vending machines. In the case of the later U.S. dollar coins, the manganese alloy was intended to duplicate the properties of the copper/nickel alloy used in the previous [[Astronomy:Susan B. Anthony dollar|Susan B. Anthony dollar]].

Manganese compounds have been used as pigments and for the coloring of ceramics and glass. The brown color of ceramic is sometimes the result of manganese compounds.<ref>{{cite book|title=Ceramics for the Archaeologist|first=Anna Osler|last=Shepard|publisher=Carnegie Institution of Washington|date=1956|pages=40–42|isbn=978-0-87279-620-1|chapter=Manganese and Iron–Manganese Paints}}</ref> In the glass industry, manganese compounds are used for two effects. [[Chemistry:Manganese(III) oxide|Manganese(III)]] reacts with [[Chemistry:Iron(II) oxide|iron(II)]] to reduce strong green color in glass by forming less-colored iron(III) and slightly pink manganese(II), compensating for the residual color of the iron(III).<ref name="ItGlass" /> Larger quantities of manganese are used to produce pink colored glass. In 2009, Professor Mas Subramanian and associates at [[Organization:Oregon State University|Oregon State University]] discovered that manganese can be combined with [[Chemistry:Yttrium|yttrium]] and [[Chemistry:Indium|indium]] to form an intensely [[Blue|blue]], non-toxic, inert, fade-resistant pigment, YInMn blue, the first new blue pigment discovered in 200 years.{{citation needed|date=February 2023}}

==Biochemistry==
[[File:Arginase.jpeg|thumb|upright=1.3|Reactive center of arginase with boronic acid [[Biology:Enzyme inhibitor|inhibitor]] – the manganese atoms are shown in yellow.]]{{Main|Manganese in biology}}

Many classes of [[Biology:Enzyme|enzyme]]s contain manganese [[Biology:Cofactor (biochemistry)|cofactors]] including [[Biology:Oxidoreductase|oxidoreductase]]s, [[Biology:Transferase|transferase]]s, [[Biology:Hydrolase|hydrolase]]s, [[Biology:Lyase|lyase]]s, [[Biology:Isomerase|isomerase]]s and [[Biology:Ligase|ligase]]s. Other enzymes containing manganese are [[Biology:Arginase|arginase]] and a Mn-containing [[Biology:Superoxide dismutase|superoxide dismutase]] (Mn-SOD). Some [[Biology:Reverse transcriptase|reverse transcriptase]]s of many [[Biology:Retrovirus|retrovirus]]es (although not [[Biology:Lentivirus|lentivirus]]es such as [[Biology:HIV|HIV]]) contain manganese. Manganese-containing polypeptides are the [[Biology:Diphtheria toxin|diphtheria toxin]], [[Biology:Lectin|lectin]]s, and [[Biology:Integrin|integrin]]s.<ref name="Mnzym">{{cite journal |doi=10.1021/acs.accounts.7b00343 |title=Manganese–Oxygen Intermediates in O–O Bond Activation and Hydrogen-Atom Transfer Reactions |year=2017 |last1=Rice |first1=Derek B. |last2=Massie |first2=Allyssa A. |last3=Jackson |first3=Timothy A. |journal=Accounts of Chemical Research |volume=50 |issue=11 |pages=2706–2717 |pmid=29064667 }}</ref>

The [[Biology:Oxygen-evolving complex|oxygen-evolving complex]] (OEC), containing four atoms of manganese, is a part of photosystem II contained in the thylakoid membranes of chloroplasts.  The OEC is responsible for the terminal [[Biology:Oxygen evolution|photooxidation of water]] during the light reactions of [[Earth:Photosynthesis|photosynthesis]], i.e., it is the catalyst that makes the O2 produced by plants.<ref>{{cite journal|last1=Umena|first1=Yasufumi|last2=Kawakami|first2=Keisuke|last3=Shen|first3=Jian-Ren|last4=Kamiya |first4=Nobuo|title=Crystal structure of oxygen-evolving photosystem II at a resolution of 1.9 Å|journal=Nature|volume=473|issue=7345|pages=55–60|doi=10.1038/nature09913|pmid=21499260|date=May 2011|bibcode=2011Natur.473...55U|s2cid=205224374|url=http://ousar.lib.okayama-u.ac.jp/files/public/4/47455/20160528084139320094/Nature_473_55–60.pdf}}</ref><ref>{{cite encyclopedia|last=Dismukes|first=G. Charles|author2=Willigen, Rogier T. van|title=Manganese: The Oxygen-Evolving Complex & Models Based in part on the article Manganese: Oxygen-Evolving Complex & Models by Lars-Erik Andréasson & Tore Vänngård which appeared in the Encyclopedia of Inorganic Chemistry, First Edition, First Edition|date=2006|encyclopedia=Encyclopedia of Inorganic Chemistry|doi=10.1002/0470862106.ia128|chapter=Manganese: The Oxygen-Evolving Complex & Models|isbn=978-0470860786}}</ref> 

==Human health and nutrition ==
Manganese is an essential human dietary element. It is present as a coenzyme in several biological processes, which include macronutrient metabolism, bone formation, and [[Biology:Free radical|free radical]] defense systems. It is a critical component in dozens of proteins and enzymes.<ref name="Erikson-2019">{{cite book 
|last1=Erikson|first1=Keith M. |last2=Ascher |first2=Michael
|editor1-last=Sigel|editor1-first=Astrid
|editor2-last=Freisinger|editor2-first=Eva
|editor3-last=Sigel|editor3-first=Roland K. O. 
|editor4-last=Carver|editor4-first=Peggy L. 
|title=Essential Metals in Medicine:Therapeutic Use and Toxicity of Metal Ions in the Clinic
|journal=Metal Ions in Life Sciences |volume=19 |date=2019 |publisher=de Gruyter GmbH|location=Berlin
|isbn=978-3-11-052691-2
|doi=10.1515/9783110527872-016
|pmid=30855111
|pages=253–266|chapter=Chapter 10. Manganese: Its Role in Disease and Health|s2cid=73725546 }}
</ref> The human body contains about 12&nbsp;mg of manganese, mostly in the bones. The soft tissue remainder is concentrated in the liver and kidneys.<ref name="Emsley2001" /> In the human brain, the manganese is bound to manganese [[Biology:Metalloprotein|metalloprotein]]s, most notably [[Biology:Glutamine synthetase|glutamine synthetase]] in [[Biology:Astrocyte|astrocyte]]s.<ref>{{cite journal|doi=10.1016/S0165-0173(02)00234-5|title=Manganese action in brain function|date=2003 |last=Takeda |first=A.|journal=Brain Research Reviews|volume=41|issue=1|pmid=12505649|pages=79–87|s2cid=1922613}}</ref>

<div style="float: right; margin: 2px; font-size:85%;">
{| class="wikitable"
|+Current AIs of Mn by age group and sex<ref name="MnDRI" />
!colspan="2"|Males
!colspan="2"|Females
|-
!Age
!AI (mg/day)
!Age
!AI (mg/day)
|-
|1–3
|1.2
|1–3
|1.2
|-
|4–8
|1.5
|4–8
|1.5
|-
|9–13
|1.9
|9–13
|1.6
|-
|14–18
|2.2
|14–18
|1.6
|-
|rowspan=3|19+
|rowspan=3|2.3
|rowspan=3|19+
|1.8
|-
|pregnant: 2
|-
|lactating: 2.6
|}</div>

===Enzymes===

* [[Biology:Superoxide dismutase#Human|Manganese superoxide dismutase (Mn-SOD)]]

===Regulation===
The U.S. Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for minerals in 2001. For manganese there was not sufficient information to set EARs and RDAs, so needs are described as estimates for Adequate Intakes (AIs). As for safety, the IOM sets Tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. In the case of manganese the adult UL is set at 11&nbsp;mg/day. Collectively the EARs, RDAs, AIs and ULs are referred to as [[Chemistry:Dietary Reference Intake|Dietary Reference Intake]]s (DRIs).<ref name="MnDRI">{{cite book|chapter=Manganese|chapter-url=https://www.nap.edu/read/10026/chapter/12 |title=Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Chromium, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Chromium|publisher= National Academy Press|year= 2001|pages=394–419|pmid=25057538|isbn=978-0-309-07279-3|author1=Institute of Medicine (US) Panel on Micronutrients }}</ref> Manganese deficiency is rare.<ref>''See'' {{cite web|url=http://lpi.oregonstate.edu/mic/minerals/manganese |title=Manganese|work=Micronutrient Information Center|publisher=[[Organization:Oregon State University|Oregon State University]] Linus Pauling Institute|date=23 April 2014}}</ref>

The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL defined the same as in United States. For people ages 15 and older the AI is set at 3.0&nbsp;mg/day. AIs for pregnancy and lactation is 3.0&nbsp;mg/day. For children ages 1–14 years the AIs increase with age from 0.5 to 2.0&nbsp;mg/day. The adult AIs are higher than the U.S. RDAs.<ref>{{cite web | title = Overview on Dietary Reference Values for the EU population as derived by the EFSA Panel on Dietetic Products, Nutrition and Allergies| year = 2017| url = https://www.efsa.europa.eu/sites/default/files/assets/DRV_Summary_tables_jan_17.pdf}}</ref> The EFSA reviewed the same safety question and decided that there was insufficient information to set a UL.<ref>{{citation| title = Tolerable Upper Intake Levels For Vitamins And Minerals| publisher = European Food Safety Authority| year = 2006| url = http://www.efsa.europa.eu/sites/default/files/efsa_rep/blobserver_assets/ndatolerableuil.pdf}}</ref>

For U.S. food and dietary supplement labeling purposes the amount in a serving is expressed as a percent of Daily Value (%DV). For manganese labeling purposes 100% of the Daily Value was 2.0&nbsp;mg, but as of 27&nbsp;May 2016 it was revised to 2.3&nbsp;mg to bring it into agreement with the RDA.<ref name="FedReg">{{cite web|url=https://www.gpo.gov/fdsys/pkg/FR-2016-05-27/pdf/2016-11867.pdf |title=Federal Register May 27, 2016 Food Labeling: Revision of the Nutrition and Supplement Facts Labels. FR page 33982.}}</ref><ref>{{cite web | title=Daily Value Reference of the Dietary Supplement Label Database (DSLD) | website=Dietary Supplement Label Database (DSLD) | url=https://www.dsld.nlm.nih.gov/dsld/dailyvalue.jsp | access-date=16 May 2020 | archive-date=7 April 2020 | archive-url=https://web.archive.org/web/20200407073956/https://dsld.nlm.nih.gov/dsld/dailyvalue.jsp | url-status=dead }}</ref> A table of the old and new adult daily values is provided at [[Chemistry:Reference Daily Intake|Reference Daily Intake]].

Excessive exposure or intake may lead to a condition known as [[Medicine:Manganism|manganism]], a [[Medicine:Neurodegeneration|neurodegenerative]] disorder that causes [[Biology:Dopamine|dopamine]]rgic neuronal death and symptoms similar to [[Medicine:Parkinson's disease|Parkinson's disease]].<ref name="Emsley2001" /><ref>{{cite book |first1=Daiana|last1=Silva Avila|first2=Robson|last2=Luiz Puntel|first3=Michael|last3=Aschner|chapter=Manganese in Health and Disease |editor=Astrid Sigel|editor2=Helmut Sigel |editor3=Roland K. O. Sigel|title=Interrelations between Essential Metal Ions and Human Diseases|series=Metal Ions in Life Sciences
|volume=13|date=2013|publisher=Springer|pages=199–227|doi=10.1007/978-94-007-7500-8_7|pmid=24470093|pmc=6589086|isbn=978-94-007-7499-5}}</ref>

=== Deficiency ===
Manganese deficiency in humans, which is rare, results in a number of medical problems.  A deficiency of manganese causes skeletal deformation in animals and inhibits the production of collagen in wound healing.<ref>{{cite journal |last1=Wang |first1=Cui-Yue |last2=Xia |first2=Wei-Hao |last3=Wang |first3=Lin |last4=Wang |first4=Zhen-Yong |title=Manganese deficiency induces avian tibial dyschondroplasia by inhibiting chondrocyte proliferation and differentiation |url=https://www.sciencedirect.com/science/article/abs/pii/S0034528821002691 |journal=Research in Veterinary Science |pages=164–170 |doi=10.1016/j.rvsc.2021.08.018 |date=1 November 2021|volume=140 |pmid=34481207 }}</ref>

==Exposure==
===In water===
Waterborne manganese has a greater [[Chemistry:Bioavailability|bioavailability]] than dietary manganese. According to results from a 2010 study,<ref name="Bouchard 138–143">{{cite journal|doi=10.1289/ehp.1002321 |volume=119|pages=138–143|pmid=20855239 |issue=1 |pmc=3018493|year=2011 |last1=Bouchard |first1=M. F |title=Intellectual impairment in school-age children exposed to manganese from drinking water |journal=Environmental Health Perspectives |last2=Sauvé |first2=S |last3=Barbeau |first3=B |last4=Legrand |first4=M |last5=Bouffard |first5=T |last6=Limoges |first6=E |last7=Bellinger |first7=D. C |last8=Mergler |first8=D }}</ref> higher levels of exposure to manganese in drinking water are associated with increased intellectual impairment and reduced [[Philosophy:Intelligence quotient|intelligence quotient]]s in school-age children. It is hypothesized that long-term exposure due to inhaling the naturally occurring manganese in shower water puts up to 8.7&nbsp;million Americans at risk.<ref>{{cite journal|doi=10.1081/CLT-100102427|pmid=10382563|title=Manganese|date=1999 |author=Barceloux, Donald |journal=Clinical Toxicology|volume=37|last2=Barceloux|first2=Donald|issue=2|pages=293–307}}</ref> However, data indicates that the human body can recover from certain adverse effects of overexposure to manganese if the exposure is stopped and the body can clear the excess.<ref>{{cite journal|pmid=8143974 |year=1994 |last1=Devenyi |first1=A. G |title=Dystonia, hyperintense basal ganglia, and high whole blood manganese levels in Alagille's syndrome |journal=Gastroenterology |volume=106 |issue=4 |pages=1068–71 |last2=Barron |first2=T. F |last3=Mamourian |first3=A. C |doi=10.1016/0016-5085(94)90769-2|s2cid=2711273 }}</ref>

Mn levels can increase in seawater is when hypoxic periods occur.<ref>{{Cite journal|last1=Hernroth|first1=Bodil|last2=Krång|first2=Anna-Sara|last3=Baden|first3=Susanne|date=February 2015|title=Bacteriostatic suppression in Norway lobster (Nephrops norvegicus) exposed to manganese or hypoxia under pressure of ocean acidification|url=http://dx.doi.org/10.1016/j.aquatox.2014.11.025|journal=Aquatic Toxicology|volume=159|pages=217–224|doi=10.1016/j.aquatox.2014.11.025|pmid=25553539|bibcode=2015AqTox.159..217H |issn=0166-445X}}</ref> Since 1990 there have been reports of Mn accumulation in marine organisms including fish, crustaceans, mollusks, and echinoderms. Specific tissues are targets in different species, including the gills, brain, blood, kidney, and liver/[[Biology:Hepatopancreas|hepatopancreas]]. Physiological effects have been reported in these species. Mn can affect the renewal of immunocytes and their functionality, such as [[Biology:Phagocytosis|phagocytosis]] and activation of [[Biology:Prophenoloxidase|pro-phenoloxidase]], suppressing the organisms' immune systems. This causes the organisms to be more susceptible to infections. As climate change occurs, pathogen distributions increase, and in order for organisms to survive and defend themselves against these pathogens, they need a healthy, strong immune system. If their systems are compromised from high Mn levels, they will not be able to fight off these pathogens and die.<ref name="Hernroth-2020" />

===Gasoline===
[[File:Methylcyclopentadienyl manganese tricarbonyl.tif|thumb|upright|Molecular model of methylcyclopentadienyl manganese tricarbonyl (MMT)]]
[[Chemistry:Methylcyclopentadienyl manganese tricarbonyl|Methylcyclopentadienyl manganese tricarbonyl]] (MMT) is an additive developed to replace lead compounds for gasolines to improve the octane rating.  MMT is used only in a few countries. Fuels containing manganese tend to form manganese carbides, which damage exhaust valves. 

===Air===
Compared to 1953, levels of manganese in air have dropped.<ref>Agency for Toxic Substances and Disease Registry (2012) [http://www.atsdr.cdc.gov/toxprofiles/tp151-c6.pdf 6. Potential for human exposure], in [https://www.atsdr.cdc.gov/toxprofiledocs/index.html?id=102&tid=23 ''Toxicological Profile for Manganese''], Atlanta, GA: U.S. Department of Health and Human Services.</ref> Generally, exposure to ambient Mn air concentrations in excess of 5&nbsp;μg Mn/m<sup>3</sup> can lead to Mn-induced symptoms. Increased [[Biology:Ferroportin|ferroportin]] protein expression in human embryonic kidney (HEK293) cells is associated with decreased intracellular Mn concentration and attenuated [[Biology:Cytotoxicity|cytotoxicity]], characterized by the reversal of Mn-reduced glutamate uptake and diminished [[Biology:Lactate dehydrogenase|lactate dehydrogenase]] leakage.<ref>{{cite journal|pmid=20002294|last1=Yin|first1=Z.|date=2010|pages=1190–8|issue=5|volume=112|last2=Jiang|first2=H.|journal=Journal of Neurochemistry|last3=Lee|first3=E. S.|last4=Ni|first4=M.|last5=Erikson|first5=K. M.|last6=Milatovic|first6=D.|last7=Bowman|first7=A. B.|last8=Aschner|first8=M.|title=Ferroportin is a manganese-responsive protein that decreases manganese cytotoxicity and accumulation |url=http://libres.uncg.edu/ir/uncg/f/K_Erickson_Ferroportin_2009.pdf|pmc=2819584|doi=10.1111/j.1471-4159.2009.06534.x}}</ref>

===Regulation===
Manganese exposure in {{wipe|United States}} is regulated by the [[Organization:Occupational Safety and Health Administration|Occupational Safety and Health Administration]] (OSHA).<ref name="osha.gov">{{cite web|title=Safety and Health Topics: Manganese Compounds (as Mn)|url=https://www.osha.gov/dts/chemicalsampling/data/CH_250190.html|publisher=U.S. [[Organization:Occupational Safety and Health Administration|Occupational Safety and Health Administration]]}}</ref> People can be exposed to manganese in the workplace by breathing it in or swallowing it. OSHA has set the legal limit ([[Earth:Permissible exposure limit|permissible exposure limit]]) for manganese exposure in the workplace as 5&nbsp;mg/m<sup>3</sup> over an 8-hour workday. The [[Organization:National Institute for Occupational Safety and Health|National Institute for Occupational Safety and Health]] (NIOSH) has set a [[Earth:Recommended exposure limit|recommended exposure limit]] (REL) of 1&nbsp;mg/m<sup>3</sup> over an 8-hour workday and a short term limit of 3&nbsp;mg/m<sup>3</sup>. At levels of 500&nbsp;mg/m<sup>3</sup>, manganese is immediately dangerous to life and health.<ref>{{cite web|title=NIOSH Pocket Guide to Chemical Hazards – Manganese compounds and fume (as Mn)|url=https://www.cdc.gov/niosh/npg/npgd0379.html|publisher=Centers for Disease Control|access-date=19 November 2015}}</ref>

==Health and safety==
Manganese is essential for human health, albeit in milligram amounts.

The current maximum safe concentration under U.S. EPA rules is 50&nbsp;μg Mn/L.<ref name="EPA drinking water">{{cite web|title=Drinking Water Contaminants|url=http://water.epa.gov/drink/contaminants/index.cfm|publisher=US EPA|access-date=2 February 2015}}</ref>

===Manganism===
Manganese overexposure is most frequently associated with [[Medicine:Manganism|manganism]], a rare neurological disorder associated with excessive manganese ingestion or inhalation. Historically, persons employed in the production or processing of manganese alloys<ref>Baselt, R. (2008) ''Disposition of Toxic Drugs and Chemicals in Man'', 8th edition, Biomedical Publications, Foster City, CA, pp. 883–886, {{ISBN|0-9626523-7-7}}.</ref><ref>{{cite journal|doi=10.1023/A:1021970120965|date=2002|author=Normandin, Louise|journal=Metabolic Brain Disease |volume=17|pages=375–87|pmid=12602514|last2=Hazell|first2=A. S.|title=Manganese neurotoxicity: an update of pathophysiologic mechanisms |issue=4|s2cid=23679769}}</ref> have been at risk for developing manganism; however, health and safety regulations protect workers in developed nations.<ref name="osha.gov" /> The disorder was first described in 1837 by British academic John Couper, who studied two patients who were manganese grinders.<ref name="Couper 1837 41–42">{{cite journal|last=Couper|first=John|title=On the effects of black oxide of manganese when inhaled into the lungs|journal=Br. Ann. Med. Pharm. Vital. Stat. Gen. Sci.|date=1837|volume=1 |pages=41–42}}</ref>

Manganism is a biphasic disorder. In its early stages, an intoxicated person may experience depression, mood swings, compulsive behaviors, and psychosis. Early neurological symptoms give way to late-stage manganism, which resembles [[Medicine:Parkinson's disease|Parkinson's disease]]. Symptoms include weakness, monotone and slowed speech, an expressionless face, tremor, forward-leaning gait, inability to walk backwards without falling, rigidity, and general problems with dexterity, gait and balance.<ref name="Couper 1837 41–42" /><ref name="Cersosimo 2007 340–346">{{cite journal|last=Cersosimo|first=M. G.|author2=Koller, W.C.|title=The diagnosis of manganese-induced parkinsonism |journal=NeuroToxicology|date=2007|volume=27|pages=340–346|doi=10.1016/j.neuro.2005.10.006|pmid=16325915|issue=3}}</ref> Unlike [[Medicine:Parkinson's disease|Parkinson's disease]], manganism is not associated with loss of the sense of smell and patients are typically unresponsive to treatment with [[Chemistry:L-DOPA|L-DOPA]].<ref>{{cite journal|last=Lu|first=C. S.|author2=Huang, C.C |author3=Chu, N.S. |author4=Calne, D.B. |title=Levodopa failure in chronic manganism|journal=Neurology|date=1994|volume=44|pages=1600–1602|doi=10.1212/WNL.44.9.1600|pmid=7936281|issue=9|s2cid=38040913}}</ref> Symptoms of late-stage manganism become more severe over time even if the source of exposure is removed and brain manganese levels return to normal.<ref name="Cersosimo 2007 340–346" />

Chronic manganese exposure has been shown to produce a parkinsonism-like illness characterized by movement abnormalities.<ref name="Guilarte2015">{{cite journal | vauthors = Guilarte TR, Gonzales KK | title = Manganese-Induced Parkinsonism Is Not Idiopathic Parkinson's Disease: Environmental and Genetic Evidence | journal = Toxicological Sciences| volume = 146 | issue = 2 | pages = 204–12 | date = August 2015 | pmid = 26220508 | pmc = 4607750 | doi = 10.1093/toxsci/kfv099 | type= Review}}</ref> This condition is not responsive to typical therapies used in the treatment of PD, suggesting an alternative pathway than the typical [[Biology:Dopamine|dopamine]]rgic loss within the [[Biology:Substantia nigra|substantia nigra]].<ref name="Guilarte2015" /> Manganese may accumulate in the [[Biology:Basal ganglia|basal ganglia]], leading to the abnormal movements.<ref name="Kwakye2015">{{cite journal | vauthors = Kwakye GF, Paoliello MM, Mukhopadhyay S, Bowman AB, Aschner M | title = Manganese-Induced Parkinsonism and Parkinson's Disease: Shared and Distinguishable Features | journal = Int J Environ Res Public Health | volume = 12 | issue = 7 | pages = 7519–40 | date = July 2015 | pmid = 26154659 | pmc = 4515672 | doi = 10.3390/ijerph120707519 | type= Review | doi-access = free }}</ref> A mutation of the SLC30A10 gene, a manganese efflux transporter necessary for decreasing intracellular Mn, has been linked with the development of this Parkinsonism-like disease.<ref name="Peres2016">{{cite journal | vauthors = Peres TV, Schettinger MR, Chen P, Carvalho F, Avila DS, Bowman AB, Aschner M | title = Manganese-induced neurotoxicity: a review of its behavioral consequences and neuroprotective strategies | journal = BMC Pharmacology & Toxicology| volume = 17 | issue = 1 | pages = 57 | date = November 2016 | pmid = 27814772 | pmc = 5097420 | doi = 10.1186/s40360-016-0099-0 | type= Review | doi-access = free }}</ref> The Lewy bodies typical to PD are not seen in Mn-induced parkinsonism.<ref name="Kwakye2015" />

Animal experiments have given the opportunity to examine the consequences of manganese overexposure under controlled conditions. In (non-aggressive) rats, manganese induces mouse-killing behavior.<ref>{{cite journal|last1=Lazrishvili|display-authors=0|first1=I.|title=Manganese loading induces mouse-killing behaviour in nonaggressive rats|journal= Journal of Biological Physics and Chemistry|date=2016|volume=16|issue=3|pages=137–141 |doi=10.4024/31LA14L.jbpc.16.03}}</ref>

===Toxicity===
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Manganese compounds are less toxic than those of other widespread metals, such as [[Chemistry:Nickel|nickel]] and [[Chemistry:Copper|copper]].<ref>{{cite book|pages=31 |title=Manganese|first=Heather|last=Hasan|publisher=The Rosen Publishing Group|date=2008|isbn=978-1-4042-1408-8 |url=https://books.google.com/books?id=nRmpEaudmTYC&pg=PA31}}</ref> However, exposure to manganese dusts and fumes should not exceed the ceiling value of 5&nbsp;mg/m<sup>3</sup> even for short periods because of its toxicity level.<ref>{{cite web|url=http://www.environmentwriter.org/resources/backissues/chemicals/manganese.htm |archive-url=https://web.archive.org/web/20060828211701/http://www.environmentwriter.org/resources/backissues/chemicals/manganese.htm |url-status=dead |archive-date=28 August 2006 |title=Manganese Chemical Background |access-date=30 April 2008 |publisher=Metcalf Institute for Marine and Environmental Reporting University of Rhode Island |date=April 2006 }}</ref> <!--Manganese poses a particular risk for children due to its propensity to bind to CH-7 receptors.{{Clarify|date=September 2011}}--> Manganese poisoning has been linked to impaired motor skills and [[Medicine:Cognitive disorder|cognitive disorder]]s.<ref>{{cite web|url=http://rais.ornl.gov/tox/profiles/mn.html|publisher=Oak Ridge National Laboratory|title=Risk Assessment Information System Toxicity Summary for Manganese|access-date=23 April 2008}}</ref>

===Neurodegenerative diseases===
A protein called [[Biology:DMT1|DMT1]] is the major transporter in manganese absorption from the intestine and may be the major transporter of manganese across the [[Biology:Blood–brain barrier|blood–brain barrier]]. DMT1 also transports inhaled manganese across the nasal [[Biology:Epithelium|epithelium]]. The proposed mechanism for manganese toxicity is that dysregulation leads to [[Biology:Oxidative stress|oxidative stress]], mitochondrial dysfunction, glutamate-mediated [[Biology:Excitotoxicity|excitotoxicity]], and aggregation of proteins.<ref>{{Cite journal|last1=Prabhakaran|first1=K.|last2=Ghosh|first2=D.|last3=Chapman|first3=G.D.|last4=Gunasekar|first4=P.G.|date=2008|title=Molecular mechanism of manganese exposure-induced dopaminergic toxicity|journal=Brain Research Bulletin|volume=76|issue=4|pages=361–367|doi=10.1016/j.brainresbull.2008.03.004|pmid=18502311|s2cid=206339744|issn=0361-9230}}</ref>

==See also==
* [[Biology:Manganese exporter|Manganese exporter]], membrane transport protein
* [[Chemistry:List of countries by manganese production|List of countries by manganese production]]
* [[Engineering:Parkerizing|Parkerizing]]

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

==External links==
* [http://www.npi.gov.au/substances/manganese/index.html National Pollutant Inventory – Manganese and compounds Fact Sheet]
* [http://www.manganese.org International Manganese Institute]
* [https://www.cdc.gov/niosh/topics/manganese/ NIOSH Manganese Topic Page]
* [http://www.periodicvideos.com/videos/025.htm Manganese] at ''The Periodic Table of Videos'' (University of Nottingham)
* [https://www.manganese-dendrite.com All about Manganese Dendrites]
* [https://www.epa.gov/smm/electric-arc-furnace-eaf-slag Electric Arc Furnace (EAF) Slag]

{{Periodic table (navbox)}}
{{Manganese compounds}}
{{Manganese minerals}}

[[Category:Manganese| ]]
[[Category:Chemical elements]]
[[Category:Transition metals]]
[[Category:Deoxidizers]]
[[Category:Dietary minerals]]
[[Category:Reducing agents]]
[[Category:Native element minerals]]

{{Sourceattribution|Manganese}}