View source for Group 7 element

{{Short description|Group of chemical elements}}
{{for|the group VIIA ([[Group (periodic table)#CAS and old IUPAC numbering (A/B)|CAS]]), also referred to as "Group 7"|Halogen}}
{{Infobox periodic table group
| title       = Group&nbsp;7 {{nowrap|in the periodic table}}
| group number= 7
| trivial name=
| by element  = manganese group
| CAS         = VIIB
| old IUPAC   = VIIA
| mark        = Mn,Tc,Re,Bh
| left        = [[Group 6 element|group 6]]
| right       = [[Group 8 element|group 8]]
}}
{| class="floatright"
! colspan=2 style="text-align:left;" | ↓&nbsp;<small>[[Period (periodic table)|Period]]</small>
|-
! [[Period 4 element|4]]
| {{element cell image|25|Manganese|Mn| |Solid|Transition metal|Primordial|image=Manganese_electrolytic_and_1cm3_cube.jpg|image caption=Manganese}}
|-
! [[Period 5 element|5]]
| {{element cell image|43|Technetium|Tc| |Solid|Transition metal|From decay|image=Technetium-sample-cropped.jpg|image caption=Technetium}}
|-
! [[Period 6 element|6]]
| {{element cell image|75|Rhenium|Re| |Solid|Transition metal|Primordial|image=Rhenium single crystal bar and 1cm3 cube.jpg|image caption=Rhenium bar}}
|-
! [[Period 7 element|7]]
| {{element cell image|107|Bohrium|Bh| |Unknown phase|Transition metal|Synthetic}}
|-
| colspan="2"|
----
''Legend''
{| style="text-align:center; border:0; margin: 0 auto"
|-
| style="border:{{element color|Primordial}}; background:{{Element color|table mark}}; padding:0 2px;" | [[primordial element]]
|-
| style="border:{{element color|from decay}}; background:{{Element color|table mark}}; padding:0 2px;" | [[radioactive decay|element by radioactive decay]]
|-
| style="border:{{element color|Synthetic}}; background:{{Element color|table mark}}; padding:0 2px;" | [[synthetic element]]
|}
|}

'''Group 7''', numbered by [[International Union of Pure and Applied Chemistry|IUPAC]] nomenclature, is a [[Group (periodic table)|group of elements]] in the [[periodic table]]. It contains [[manganese]] (Mn), [[technetium]] (Tc), [[rhenium]] (Re) and [[bohrium]] (Bh). This group lies in the [[d-block]] of the periodic table, and are hence [[transition metal]]s. This group is sometimes called the '''manganese group''' or '''manganese family''' after its lightest member; however, the group itself has not acquired a [[trivial name]] because it belongs to the broader grouping of the transition metals.

The group 7 elements tend to have a major group [[oxidation state]] (+7), although this trend is markedly less coherent than the previous groups. Like other groups, the members of this family show patterns in their [[electron configuration]]s, especially the outermost shells resulting in trends in chemical behavior. In nature, manganese is a fairly common element, whereas rhenium is rare, technetium only occurs in trace quantities, and bohrium is entirely [[synthetic element|synthetic]].

== Physical properties ==

The trends in group 7 follow, although less noticeably, those of the other early d-block groups and reflect the addition of a filled f-shell into the core in passing from the fifth to the sixth period. All group 7 elements crystallize in the [[hexagonal close packed]] (hcp) structure except manganese, which crystallizes in the [[body centered cubic]] (bcc) structure. Bohrium is also expected to crystallize in the hcp structure.<ref name=bh-hcp>{{cite journal|doi=10.1103/PhysRevB.84.113104|title=First-principles calculation of the structural stability of 6d transition metals|year=2011|last1=Östlin|first1=A.|last2=Vitos|first2=L.|journal=Physical Review B|volume=84|issue=11|article-number=113104 |bibcode=2011PhRvB..84k3104O}}</ref>

The table below is a summary of the key physical properties of the group 7 elements. The properties of bohrium are either unknown or predicted, as they have not been measured.<ref name="Haire" />

{| class="wikitable centered plainrowheaders" style="text-align:center;"
|+Properties of the group 7 elements | Properties of the group 7 elements
! scope="col" | Name
! scope="col" | Mn, [[manganese]]
! scope="col" | Tc, [[technetium]]
! scope="col" | Re, [[rhenium]]
! scope="col" | Bh, [[bohrium]]
|-
! scope="row" |[[Melting point]]
| 1519 K (1246&nbsp;°C) || 2430 K (2157&nbsp;°C) || 3459 K (3186&nbsp;°C) || {{Unknown}}
|-
! scope="row" |[[Boiling point]]
| 2334 K (2061&nbsp;°C) || 4538 K (4265&nbsp;°C) || 5903 K (5630&nbsp;°C) || {{Unknown}}
|-
! scope="row" |[[Density]]
| 7.21&nbsp;g·cm<sup>−3</sup> || 11&nbsp;g·cm<sup>−3</sup> || 21.02&nbsp;g·cm<sup>−3</sup> || 26-27&nbsp;g·cm<sup>−3</sup>?<ref name=density>{{cite journal |last1=Gyanchandani |first1=Jyoti |last2=Sikka |first2=S. K. |title=Physical properties of the 6 d -series elements from density functional theory: Close similarity to lighter transition metals |journal=Physical Review B |date=10 May 2011 |volume=83 |issue=17 |article-number=172101 |doi=10.1103/PhysRevB.83.172101 |bibcode=2011PhRvB..83q2101G }}</ref><ref name=kratz>{{cite book |last1=Kratz |last2=Lieser |title=Nuclear and Radiochemistry: Fundamentals and Applications |date=2013 |page=631 |edition=3rd}}</ref>
|-
! scope="row" |Appearance
| silvery metallic || silvery-gray ||  silvery-gray || {{Unknown}}
|-
! scope="row" |[[Atomic radius]]
|  127 pm || 136 pm || 137 pm || 128 pm?<ref name="Haire" />
|}

== Chemical properties ==

Like other groups, the members of this family show patterns in its [[electron configuration]], especially the outermost shells:

{| class="wikitable" style="white-space:nowrap;"
|-
!''[[Atomic number|Z]]'' !! [[Chemical element|Element]] !! Electrons per [[Electron shell|shell]]
|-
| 25 || manganese || 2, 8, 13, 2
|-
| 43 || technetium || 2, 8, 18, 13, 2
|-
| 75 || rhenium || 2, 8, 18, 32, 13, 2
|-
| 107 || bohrium || 2, 8, 18, 32, 32, 13, 2
|}

All the members of the group readily portray their group oxidation state of +7 and the state becomes more stable as the group is descended. Technetium also shows a stable +4 state whilst rhenium exhibits stable +4 and +3 states.

Bohrium may therefore also show these lower states as well. The higher +7 oxidation state is more likely to exist in oxyanions, such as perbohrate, BhO<sub>4</sub><sup>−</sup>, analogous to the lighter [[permanganate]], [[pertechnetate]], and [[perrhenate]]. Nevertheless, bohrium(VII) is likely to be unstable in aqueous solution, and would probably be easily reduced to the more stable bohrium(IV).<ref>{{Cite book |title=The chemistry of the actinide and transactinide elements |date=2006 |publisher=Springer |isbn=978-1-4020-3555-5 |edition=3rd |location=Dordrecht}}</ref>

== Compounds ==

=== Oxides ===

==== Manganese ====

[[File:Manganese(IV)_oxide.jpg|thumb|right|Manganese(IV) oxide]]

Manganese forms a variety of oxides: [[Manganese(II) oxide|MnO]], [[Manganese(II,III) oxide|Mn<sub>3</sub>O<sub>4</sub>]], [[Manganese(III) oxide|Mn<sub>2</sub>O<sub>3</sub>]], [[Manganese dioxide|MnO<sub>2</sub>]], MnO<sub>3</sub> and [[Manganese heptoxide|Mn<sub>2</sub>O<sub>7</sub>]]. Manganese(II) oxide is an inorganic compound that forms green crystals. Like many monoxides, MnO adopts the [[Cubic crystal system#Rock-salt structure|rock salt structure]], where cations and anions are both octahedrally coordinated. Also like many oxides, manganese(II) oxide is often [[nonstoichiometric]]: its composition can vary from MnO to MnO<sub>1.045</sub>.<ref name="G&W" />
Manganese(II,III) oxide is formed when any manganese oxide is heated in air above 1000&nbsp;°C.<ref name="G&W" /> Considerable research has centred on producing nanocrystalline Mn<sub>3</sub>O<sub>4</sub> and various syntheses that involve oxidation of Mn<sup>II</sup> or reduction of Mn<sup>VI</sup>.<ref>Hausmannite Mn<sub>3</sub>O<sub>4</sub> nanorods: synthesis, characterization and magnetic properties Jin Du et al.  Nanotechnology, (2006),17 4923-4928, {{doi| 10.1088/0957-4484/17/19/024}}</ref><ref>One-step synthesis of Mn<sub>3</sub>O<sub>4</sub> nanoparticles: Structural and magnetic study Vázquez-Olmos A.,  Redón R, Rodríguez-Gattorno G., Mata-Zamora M.E., Morales-Leal F, Fernández-Osorio A.L, Saniger J.M.   Journal of Colloid and Interface Science, 291, 1, (2005), 175-180 {{doi|10.1016/j.jcis.2005.05.005}}</ref><ref>{{Cite journal |last1=Sun |first1=Xiaoming |last2=Liu |first2=Junfeng |last3=Li |first3=Yadong |date=2006-02-20 |title=Use of Carbonaceous Polysaccharide Microspheres as Templates for Fabricating Metal Oxide Hollow Spheres |url=https://onlinelibrary.wiley.com/doi/10.1002/chem.200500660 |journal=Chemistry - A European Journal |language=en |volume=12 |issue=7 |pages=2039–2047 |doi=10.1002/chem.200500660 |pmid=16374888 |issn=0947-6539|url-access=subscription }}</ref> Manganese(III) oxide is unlike many other transition metal oxides in that it does not adopt the [[corundum]] ([[aluminium oxide|Al<sub>2</sub>O<sub>3</sub>]]) structure.<ref name="G&W" /> Two forms are generally recognized, α-Mn<sub>2</sub>O<sub>3</sub> and γ-Mn<sub>2</sub>O<sub>3</sub>,<ref name = "Wells">Wells A.F. (1984) ''Structural Inorganic Chemistry'' 5th edition Oxford Science Publications {{ISBN|0-19-855370-6}}</ref> although a high pressure form with the CaIrO<sub>3</sub> structure has been reported too.<ref>High Pressure Phase transition in Mn<sub>2</sub>O<sub>3</sub> to the CaIrO<sub>3</sub>-type Phase Santillan, J.; Shim, S. American Geophysical Union, Fall Meeting 2005, abstract #MR23B-0050</ref> Manganese(IV) oxide is a blackish or brown solid occurs naturally as the mineral [[pyrolusite]], which is the main ore of manganese and a component of [[manganese nodule]]s. The principal use for MnO<sub>2</sub> is for dry-cell [[battery (electricity)|batteries]], such as the [[alkaline battery]] and the [[zinc–carbon battery]].<ref name="G&W" /> Manganese(VII) oxide is dark green in its [[crystalline]] form. The liquid is green by reflected light and red by transmitted light.<ref name=brauer>{{cite book|author=H. Lux|chapter=Manganese(VII) Oxide|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=1|pages=1459–1460}}</ref> It is soluble in [[carbon tetrachloride]], and decomposes when in contact with water.

==== Technetium ====

[[File:Technetium(IV)_oxide.png|thumb|right|Technetium(IV) oxide]]

Technetium's main oxides are [[technetium(IV) oxide]] and [[technetium(VII) oxide]]. Technetium(IV) oxide was first produced in 1949 by electrolyzing a solution of [[ammonium pertechnetate]] under [[ammonium hydroxide]]. It has often been used to separate technetium from [[molybdenum]] and rhenium.<ref name="tc" /><ref name="radio" /><ref name="electro">{{cite journal |author1=L. B. Rogers |title=Electroseparation of Technetium from Rhenium and Molybdenum |journal=Journal of the American Chemical Society |date=1949 |volume=71 |issue=4 |pages=1507–1508 |doi=10.1021/ja01172a520 |language=en}}</ref> More efficient ways are the reduction of ammonium pertechnetate by [[zinc]] metal and [[hydrochloric acid]], [[stannous chloride]], [[hydrazine]], [[hydroxylamine]], [[ascorbic acid]],<ref name="radio">{{cite journal |author1=Edward Anders |title=THE RADIOCHEMISTRY OF TECHNETIUM |url=https://www.osti.gov/biblio/4073069 |website=OSTI.GOV |publisher=U.S. Department of Energy Office of Scientific and Technical Information |access-date=4 November 2022 |page=8 |doi=10.2172/4073069 |date=1960|osti=4073069 }}</ref> by the hydrolysis of [[potassium hexachlorotechnetate]]<ref name="magnet">{{cite journal |author1=C. M. Nelson |author2=G. E. Boyd |author3=Wm. T. Smith Jr. |title=Magnetochemistry of Technetium and Rhenium |journal=Journal of the American Chemical Society |date=1954 |volume=76 |issue=2 |pages=348–352 |doi=10.1021/ja01631a009 |publisher=ACS Publications |language=en}}</ref> or by the decomposition of ammonium pertechnetate at 700&nbsp;°C under an inert atmosphere.<ref name="tc">{{cite book |author1=A. G. Sharpe |author2=H. J. Emeléus |title=Advances in Inorganic Chemistry and Radiochemistry |date=1968 |publisher=Elsevier Science |isbn=978-0-08-057860-6 |page=21 |url=https://books.google.com/books?id=-SnCsg5jM_kC&pg=PA21}}</ref><ref name="img">{{cite thesis |author1=Bradley Covington Childs |title=Volatile Technetium Oxides: Implications for Nuclear Waste Vitrification |journal=UNLV Theses, Dissertations, Professional Papers, and Capstones |date=2017 |doi=10.34917/10985836}}</ref><ref name="at">{{cite journal |author1=Edward Andrews |title=Technetium and Astatine Chemistry |journal=Annual Review of Nuclear Science |date=1959 |volume=9 |pages=203–220 |doi=10.1146/annurev.ns.09.120159.001223 |publisher=Annual Reviews |language=en|doi-access=free |bibcode=1959ARNPS...9..203A }}</ref> It reacts with oxygen to produce technetium(VII) oxide at 450&nbsp;°C.

Technetium(VII) oxide can be prepared directly by the oxidation of technetium at 450-500&nbsp;°C.<ref>{{cite book|author1=Herrell, A. Y. |author2=Busey, R. H. |author3=Gayer, K. H. | title = Technetium(VII) Oxide, in Inorganic Syntheses| year = 1977 | volume = XVII| pages = 155–158 | isbn = 0-07-044327-0|doi=10.1002/9780470132487.ch41}}</ref> It is a rare example of a molecular binary metal oxide. Other examples are [[ruthenium(VIII) oxide]] and [[osmium(VIII) oxide]]. It adopts a [[centrosymmetric]] corner-shared bi-tetrahedral structure in which the terminal and bridging  Tc&minus;O bonds are 167pm and 184 pm respectively and the Tc&minus;O&minus;Tc angle is 180°.<ref>{{cite journal|last=Krebs|first=Bernt|title = Technetium(VII)-oxid: Ein Übergangsmetalloxid mit Molekülstruktur im festen Zustand| journal = Angewandte Chemie | year = 1969 | volume = 81| issue = 9| pages = 328–329| doi = 10.1002/ange.19690810905|bibcode=1969AngCh..81..328K}}</ref>

==== Rhenium ====

Rhenium's main oxides are [[rhenium(IV) oxide]] and [[rhenium(VII) oxide]]. Rhenium(IV) oxide is a gray to black crystalline solid that can be formed by [[comproportionation]].<ref>G. Glemser "Rhenium (IV) Oxide" Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1480.</ref> At high temperatures it undergoes [[disproportionation]]. It is a laboratory reagent that can be used as a [[catalyst]]. It adopts the [[rutile structure]]. It forms [[perrhenate]]s with alkaline [[hydrogen peroxide]] and [[oxidizing acid]]s.<ref>{{cite web |url=http://www.aaamolybdenum.com/RheniumDioxide.html |title=RHENIUM DIOXIDE - Manufacturer |publisher=Aaamolybdenum.com |access-date=2012-08-06 |archive-url=https://web.archive.org/web/20030209232809/http://www.aaamolybdenum.com/RheniumDioxide.html |archive-date=2003-02-09 }}</ref> In molten sodium hydroxide it forms sodium rhenate:<ref>G. Glemser "Sodium Rhenate (IV)" Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1483.</ref>

: 2{{nbsp}}NaOH  +  ReO<sub>2</sub>   →   Na<sub>2</sub>ReO<sub>3</sub>  +  H<sub>2</sub>O

Rhenium(VII) oxide can be formed when rhenium or its oxides or sulfides are oxidized a 500-700&nbsp;°C in air.<ref name=Schmidt>{{cite book |title=Inorganic Syntheses |year=1967 |volume=9 |last1=Schmidt |first1=Max |last2=Schmidbaur |first2=Hubert |chapter=Trimethylsilyl Perrhenate |pages=149–151 |isbn=978-0-470-13240-1 |doi=10.1002/9780470132401.ch40}}</ref> It dissolves in water to give [[perrhenic acid]]. Heating Re<sub>2</sub>O<sub>7</sub> gives rhenium(IV) oxide, signalled by the appearance of the dark blue coloration.<ref name="Brauer" /> In its solid form, Re<sub>2</sub>O<sub>7</sub> consists of alternating octahedral and tetrahedral Re centres. It is the raw material for all rhenium compounds, being the volatile fraction obtained upon roasting the host ore.<ref>{{Ullmann|doi=10.1002/14356007.a23_199|title=Rhenium and Rhenium Compounds|year=2000|last1=Georg Nadler|first1=Hans|isbn=3527306730}}</ref>

Rhenium, in addition to the +4 and +7 oxidation states, also forms a [[rhenium trioxide|trioxide]]. It can be formed by reducing rhenium(VII) oxide with [[carbon monoxide]] at 200&nbsp;C or elemental rhenium at 4000&nbsp;C.<ref>{{Citation |last1=Nechamkin |first1=H. |title=Rhenium(VI) Oxide (Rhenium Trioxide) |date=Jan 1950|url=https://onlinelibrary.wiley.com/doi/10.1002/9780470132340.ch49 |work=Inorganic Syntheses |volume=3 |pages=186–188 |editor-last=Audrieth |editor-first=Ludwig F. |access-date=2023-08-26 |edition=1 |publisher=Wiley |language=en |doi=10.1002/9780470132340.ch49 |isbn=978-0-470-13162-6 |last2=Hiskey |first2=C. F. |last3=Moeller |first3=Therald |last4=Shoemaker |first4=C. E.|url-access=subscription }}</ref> It can also be reduced with [[dioxane]].<ref name="Glemser">{{cite book|author1=O. Glemser|author2=R. Sauer|chapter=Rhenium(VI) Oxide|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY |volume=2 |page=1482 }}</ref> It is a red solid with a metallic lustre that resembles [[copper]] in appearance, and is the only stable [[trioxide]] of the group 7 elements.

=== Halides ===

==== Manganese ====

Manganese can form compounds in the +2, +3 and +4 oxidation states. The manganese(II) compounds are often light pink solids. Like some other metal difluorides, MnF<sub>2</sub> crystallizes in the [[rutile]] structure, which features octahedral Mn centers.<ref>{{cite journal |doi=10.1021/ja01650a005|title=The Crystal Structure of MnF<sub>2</sub>, FeF<sub>2</sub>, CoF<sub>2</sub>, NiF<sub>2</sub> and ZnF<sub>2</sub>|first1=J. W.|last1=Stout|first2=Stanley A.|last2=Reed|journal= J. Am. Chem. Soc.|year=1954|volume=76|issue=21|pages=5279–5281}}</ref> and it  is used in the manufacture of special kinds of [[glass]] and [[laser]]s.<ref>
{{Cite book | last1 = Ayres | first1 = D. C. | last2 = Hellier | first2 = Desmond | year = 1997 | title = Dictionary of Environmentally Important Chemicals | publisher = CRC Press | isbn = 0-7514-0256-7 | page = 195 | url = https://books.google.com/books?id=UTKWehimCkEC&q=%22Manganese(II)+fluoride+%22&pg=PA195 | access-date = 2008-06-18 }}</ref> Scacchite is the natural, anhydrous form of manganese(II) chloride.<ref>{{Cite web|url=https://www.mindat.org/min-3549.html|title=Scacchite}}</ref> The only other currently known mineral systematized as manganese chloride is kempite - a representative of the atacamite group, a group of hydroxide-chlorides.<ref>{{Cite web|url=https://www.mindat.org/min-2183.html|title=Kempite}}</ref> It can be used in place of [[palladium]] in the [[Stille reaction]], which couples two carbon atoms using an [[organotin compound]].<ref name="Mn(II) halide" /> It can be used as a pink pigment or as a source of the manganese ion or iodide ion. It is often used in the lighting industry.<ref name="Mn(II) halide">{{Cite book | last = Cepanec | first = Ivica  | year = 2004 | title = Synthesis of Biaryls | edition = | volume = | series = | publication-place =  | place =  | publisher = Elsevier | id = | isbn = 0-08-044412-1 | doi = | oclc = | page = 104 | url = https://books.google.com/books?id=UMLOo1wXWdwC&dq=%22Manganese(II)+bromide+%22&pg=PA104 | access-date = 2008-06-18 }}</ref>

==== Technetium ====

The following binary (containing only two elements) technetium halides are known: [[TcF6|TcF<sub>6</sub>]], TcF<sub>5</sub>, [[TcCl4|TcCl<sub>4</sub>]], TcBr<sub>4</sub>, TcBr<sub>3</sub>, α-TcCl<sub>3</sub>, β-TcCl<sub>3</sub>, TcI<sub>3</sub>, α-TcCl<sub>2</sub>, and β-TcCl<sub>2</sub>. The [[oxidation state]]s range from Tc(VI) to Tc(II). Technetium halides exhibit different structure types, such as molecular octahedral complexes, extended chains, layered sheets, and metal clusters arranged in a three-dimensional network.<ref>{{Cite thesis|title=Binary Technetium Halides |last=Johnstone|first=E. V. |date=May 2014 |publisher=University of Nevada, Las Vegas |url=http://digitalscholarship.unlv.edu/cgi/viewcontent.cgi?article=3100&context=thesesdissertations |doi=10.34917/5836118 |via=UNLV Theses, Dissertations, Professional Papers, and Capstones}}</ref><ref name="AS">{{cite journal|doi=10.1021/ar400225b |pmid=24393028|title=Recent Advances in Technetium Halide Chemistry|journal=Accounts of Chemical Research|volume=47|issue=2|pages=624–632 |year=2014|last1=Poineau |first1=Frederic|last2=Johnstone|first2=Erik V.|last3=Czerwinski|first3=Kenneth R.|last4=Sattelberger |first4=Alfred P.}}</ref> These compounds are produced by combining the metal and halogen or by less direct reactions.

TcCl<sub>4</sub> is obtained by chlorination of Tc metal or Tc<sub>2</sub>O<sub>7</sub> Upon heating, TcCl<sub>4</sub> gives the corresponding Tc(III) and Tc(II) chlorides.<ref name="AS" />
:TcCl<sub>4</sub> → α-TcCl<sub>3</sub> + 1/2 Cl<sub>2</sub>
:TcCl<sub>3</sub> → β-TcCl<sub>2</sub> + 1/2 Cl<sub>2</sub>
The structure of TcCl<sub>4</sub> is composed of infinite zigzag chains of edge-sharing TcCl<sub>6</sub> octahedra. It is isomorphous to transition metal tetrachlorides of [[zirconium]], [[hafnium]], and [[platinum]].<ref name="AS"/>
[[File:Chloro-containing coordination complexes of technetium (Tc-99).jpg|thumb|Chloro-containing coordination complexes of technetium (Tc-99) in various oxidation states: Tc(III), Tc(IV), Tc(V), and Tc(VI) represented.]]

Two polymorphs of [[technetium trichloride]] exist, α- and β-TcCl<sub>3</sub>. The α polymorph is also denoted as Tc<sub>3</sub>Cl<sub>9</sub>. It adopts a confacial [[Octahedral molecular geometry#Bioctahedral molecular geometry|bioctahedral structure]].<ref>{{cite journal|doi=10.1021/ja105730e|pmid=20977207|title=Synthesis and Structure of Technetium Trichloride|journal=Journal of the American Chemical Society|volume=132|issue=45|pages=15864–5|year=2010|last1=Poineau|first1=Frederic|last2=Johnstone|first2=Erik V.|last3=Weck|first3=Philippe F.|last4=Kim|first4=Eunja|last5=Forster|first5=Paul M.|last6=Scott|first6=Brian L.|last7=Sattelberger|first7=Alfred P.|last8=Czerwinski|first8=Kenneth R.}}</ref> It is prepared by treating the chloro-acetate Tc<sub>2</sub>(O<sub>2</sub>CCH<sub>3</sub>)<sub>4</sub>Cl<sub>2</sub> with HCl. Like [[Trirhenium nonachloride|Re<sub>3</sub>Cl<sub>9</sub>]], the structure of the α-polymorph consists of triangles with short M-M distances. β-TcCl<sub>3</sub> features octahedral Tc centers, which are organized in pairs, as seen also for [[molybdenum trichloride]]. TcBr<sub>3</sub> does not adopt the structure of either trichloride phase. Instead it has the structure of [[molybdenum tribromide]], consisting of chains of confacial octahedra with alternating short and long Tc—Tc contacts. TcI<sub>3</sub> has the same structure as the high temperature phase of [[titanium(III) iodide|TiI<sub>3</sub>]], featuring chains of confacial octahedra with equal Tc—Tc contacts.<ref name="AS" />

Several anionic technetium halides are known. The binary tetrahalides can be converted to the hexahalides [TcX<sub>6</sub>]<sup>2−</sup> (X = F, Cl, Br, I), which adopt [[octahedral molecular geometry]].<ref name="s8">{{harvnb|Schwochau|2000|pp=7–9}}</ref> More reduced halides form anionic clusters with Tc–Tc bonds. The situation is similar for the related elements of Mo, W, Re. These clusters have the nuclearity Tc<sub>4</sub>, Tc<sub>6</sub>, Tc<sub>8</sub>, and Tc<sub>13</sub>. The more stable Tc<sub>6</sub> and Tc<sub>8</sub> clusters have prism shapes where vertical pairs of Tc atoms are connected by triple bonds and the planar atoms by single bonds. Every technetium atom makes six bonds, and the remaining valence electrons can be saturated by one axial and two [[bridging ligand]] halogen atoms such as [[chlorine]] or [[bromine]].<ref>{{cite journal|first1 = K. E.|last1 = German|last2 = Kryutchkov|first2 = S. V.|title = Polynuclear Technetium Halide Clusters|journal = Russian Journal of Inorganic Chemistry|volume = 47|issue = 4|date = 2002|pages = 578–583|url = http://www.maik.rssi.ru/cgi-perl/search.pl?type=abstract&name=inrgchem&number=4&year=2&page=578|archive-url = https://web.archive.org/web/20151222111809/http://www.maik.rssi.ru/cgi-perl/search.pl?type=abstract&name=inrgchem&number=4&year=2&page=578|archive-date = 2015-12-22}}</ref>

==== Rhenium ====

The most common rhenium chlorides are [[Rhenium hexachloride|ReCl<sub>6</sub>]], [[Rhenium pentachloride|ReCl<sub>5</sub>]], [[Rhenium tetrachloride|ReCl<sub>4</sub>]], and [[Rhenium trichloride|ReCl<sub>3</sub>]].<ref name="G&W">{{Greenwood&Earnshaw2nd}}</ref> The structures of these compounds often feature extensive Re-Re bonding, which is characteristic of this metal in oxidation states lower than VII. Salts of [Re<sub>2</sub>Cl<sub>8</sub>]<sup>2−</sup> feature a [[quadruple bond|quadruple]] metal-metal bond. Although the highest rhenium chloride features Re(VI), fluorine gives the d<sup>0</sup> Re(VII) derivative [[rhenium heptafluoride]]. Bromides and iodides of rhenium are also well known.

Like tungsten and molybdenum, with which it shares chemical similarities, rhenium forms a variety of [[Oxohalide|oxyhalides]]. The oxychlorides are most common, and include ReOCl<sub>4</sub>, ReOCl<sub>3</sub>.

=== Organometallic compounds ===

==== Manganese ====

{{Main|Organomanganese chemistry}}

Organomanganese compounds were first reported in 1937 by Gilman and Bailee who described the reaction of [[phenyllithium]] and [[manganese(II) iodide]] to form phenylmanganese iodide (PhMnI) and diphenylmanganese (Ph<sub>2</sub>Mn).<ref name="Cahiez2009">{{cite journal|title=Chemistry of Organomanganese(II) Compounds|first1=Gerard|last1=Cahiez|first2=Christophe|last2=Duplais|first3=Julien|last3=Buendia|journal=[[Chem. Rev.]]|year=2009|volume=109 |issue=3 |pages=1434–1476 |doi=10.1021/cr800341a|pmid=19209933 }}</ref>

Following this precedent, other organomanganese halides can be obtained by alkylation of [[manganese(II) chloride]], [[manganese(II) bromide]], and [[manganese(II) iodide]].  Manganese iodide is attractive because the anhydrous compound can be prepared in situ from manganese and [[iodine]] in [[diethyl ether|ether]]. Typical alkylating agents are [[organolithium]] or [[organomagnesium]] compounds.

The chemistry of organometallic compounds of Mn(II) are unusual among the [[transition metal]]s due to the high ionic character of the Mn(II)-C bond.<ref>{{cite journal|first=Richard A.|last=Layfield|title=Manganese(II): The Black Sheep of the Organometallic Family|journal=[[Chem. Soc. Rev.]]|year=2008 |volume=37|issue=6|pages=1098–1107 |doi=10.1039/b708850g |pmid=18497923 }}</ref> The reactivity of organomanganese compounds can be compared to that of [[Organomagnesium chemistry|organomagnesium]] and [[organozinc compound]]s. The [[electronegativity]] of Mn (1.55) is comparable to that of Mg (1.31) and Zn (1.65), making the carbon atom (EN = 2.55) [[nucleophilic]]. The [[reduction potential]] of Mn is also intermediate between Mg and Zn.

==== Technetium ====

{{Main|Organotechnetium chemistry}}

[[File:Tc CNCH2CMe2(OMe) 6Cation.png|thumb|right|[[Technetium (99mTc) sestamibi]] ("Cardiolite") is widely used for imaging of the heart.]]
Technetium forms a variety of [[coordination complex]]es with organic ligands. Many have been well-investigated because of their relevance to [[nuclear medicine]].<ref>{{cite journal|doi=10.1021/cr1000755|pmid=20415476|title=Technetium and Gallium Derived Radiopharmaceuticals: Comparing and Contrasting the Chemistry of Two Important Radiometals for the Molecular Imaging Era|journal=Chemical Reviews|volume=110|issue=5|pages=2903–20|year=2010|last1=Bartholomä|first1=Mark D.|last2=Louie|first2=Anika S.|last3=Valliant|first3=John F.|last4=Zubieta|first4=Jon}}</ref>

Technetium forms a variety of compounds with Tc–C bonds, i.e. organotechnetium complexes. Prominent members of this class are complexes with CO, arene, and cyclopentadienyl ligands.<ref name="Alberto" /> The binary carbonyl Tc<sub>2</sub>(CO)<sub>10</sub> is a white volatile solid.<ref>{{cite journal|doi = 10.1021/ja01474a038|date = 1961|last1 = Hileman|first1 = J. C.|last2 = Huggins|last3 = Kaesz|journal = Journal of the American Chemical Society |volume = 83|title = Technetium carbonyl|pages = 2953–2954|first2 = D. K.|first3 = H. D.|issue = 13}}</ref> In this molecule, two technetium atoms are bound to each other; each atom is surrounded by [[octahedron|octahedra]] of five carbonyl ligands. The bond length between technetium atoms, 303&nbsp;pm,<ref>{{cite journal|title = The Crystal Structure of Ditechnetium Decacarbonyl|doi =10.1021/ic50030a011|date =1965|last1 =Bailey|first1 = M. F.|journal =Inorganic Chemistry|volume =4|pages =1140–1145|last2 = Dahl|first2 = Lawrence F.|issue = 8}}</ref><ref>{{cite journal|doi = 10.1107/S0365110X62002789|title = Unit cell and space group of technetium carbonyl, Tc2(CO)10|date = 1962|last1 = Wallach|first1 = D.|journal = Acta Crystallographica|volume = 15|page = 1058|issue = 10| bibcode=1962AcCry..15.1058W }}</ref> is significantly larger than the distance between two atoms in metallic technetium (272&nbsp;pm). Similar [[carbonyl]]s are formed by technetium's [[Congener (chemistry)|congeners]], manganese and rhenium.{{sfn|Schwochau|2000|pp=286, 328}} Interest in organotechnetium compounds has also been motivated by applications in [[nuclear medicine]].<ref name="Alberto">{{cite book|doi=10.1007/978-3-642-13185-1_9|chapter=Organometallic Radiopharmaceuticals|title=Medicinal Organometallic Chemistry|volume=32|pages=219–246|series=Topics in Organometallic Chemistry|year=2010 |last1=Alberto|first1=Roger|isbn=978-3-642-13184-4}}</ref> Unusual for other metal carbonyls, Tc forms aquo-carbonyl complexes, prominent being [Tc(CO)<sub>3</sub>(H<sub>2</sub>O)<sub>3</sub>]<sup>+</sup>.<ref name="Alberto" />

==== Rhenium ====

{{Main|Organorhenium chemistry}}

[[Dirhenium decacarbonyl]] is the most common entry to organorhenium chemistry. Its reduction with sodium [[Amalgam (chemistry)|amalgam]] gives Na[Re(CO)<sub>5</sub>] with rhenium in the formal oxidation state −1.<ref>{{cite journal|doi = 10.1002/cber.19901230103|title = Nucleophile Addition von Carbonylmetallaten an kationische Alkin-Komplexe [CpL2M(η2-RC≡CR)]+ (M = Ru, Fe): μ-η1:η1-Alkin-verbrückte Komplexe|date = 1990|author = Breimair, Josef|journal = Chemische Berichte|volume = 123|page = 7|last2 = Steimann|first2 = Manfred|last3 = Wagner|first3 = Barbara|last4 = Beck|first4 = Wolfgang}}</ref> Dirhenium decacarbonyl can be oxidised with [[bromine]] to [[bromopentacarbonylrhenium(I)]]:<ref>{{cite book|title=Inorganic Syntheses|first=Steven P.|last =Schmidt|author2=Trogler, William C. |author3=Basolo, Fred |chapter=Pentacarbonylrhenium Halides | volume=28|date=1990|pages=154–159|doi=10.1002/9780470132593.ch42|isbn=978-0-470-13259-3}}</ref>
:Re<sub>2</sub>(CO)<sub>10</sub> + Br<sub>2</sub> → 2 Re(CO)<sub>5</sub>Br

Reduction of this pentacarbonyl with [[zinc]] and [[acetic acid]] gives [[pentacarbonylhydridorhenium]]:<ref name="Urb">{{cite book|author=Michael A. Urbancic|author2=John R. Shapley|chapter=Pentacarbonylhydridorhenium |title=Inorganic Syntheses|volume=28|pages=165–168|date=1990|doi =10.1002/9780470132593.ch43|isbn=978-0-470-13259-3}}</ref>
:Re(CO)<sub>5</sub>Br + Zn + HOAc → Re(CO)<sub>5</sub>H + ZnBr(OAc)

[[Methylrhenium trioxide]] ("MTO"), CH<sub>3</sub>ReO<sub>3</sub> is a volatile, colourless solid has been used as a [[catalyst]] in some laboratory experiments. It can be prepared by many routes, a typical method is the reaction of Re<sub>2</sub>O<sub>7</sub> and [[tetramethyltin]]:
:Re<sub>2</sub>O<sub>7</sub> + (CH<sub>3</sub>)<sub>4</sub>Sn → CH<sub>3</sub>ReO<sub>3</sub> + (CH<sub>3</sub>)<sub>3</sub>SnOReO<sub>3</sub>
Analogous alkyl and aryl derivatives are known. MTO catalyses for the oxidations with [[hydrogen peroxide]]. Terminal [[alkyne]]s yield the corresponding acid or ester, internal alkynes yield diketones, and [[alkene]]s give epoxides. MTO also catalyses the conversion of [[aldehyde]]s and [[diazoalkane]]s into an alkene.<ref>Hudson, A. (2002) "Methyltrioxorhenium" in ''Encyclopedia of Reagents for Organic Synthesis''. John Wiley & Sons: New York, {{ISBN|9780470842898}}, {{doi|10.1002/047084289X}}.</ref>

=== Polyoxometalates ===

{{Main|Polyoxometalate#Polyoxotechnetates and rhenates}}

The polyoxotechnetate (polyoxometalate of technetium) contains both Tc(V) and Tc(VII) in ratio 4: 16 and is obtained as the [[hydronium]] salt [H<sub>7</sub>O<sub>3</sub>]<sub>4</sub>[Tc<sub>20</sub>O<sub>68</sub>]·4H<sub>2</sub>O by concentrating an HTcO<sub>4</sub> solution.<ref>{{Cite journal |last1=German |first1=Konstantin E. |last2=Fedoseev |first2=Alexander M. |last3=Grigoriev |first3=Mikhail S. |last4=Kirakosyan |first4=Gayane A. |last5=Dumas |first5=Thomas |last6=Den Auwer |first6=Christophe |last7=Moisy |first7=Philippe |last8=Lawler |first8=Keith V. |last9=Forster |first9=Paul M. |last10=Poineau |first10=Frederic |date=2021-09-24 |title=A 70-Year-Old Mystery in Technetium Chemistry Explained by the New Technetium Polyoxometalate [H 7 O 3 ] 4 [Tc 20 O 68 ] ⋅ 4H 2 O |url=https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202102035 |journal=Chemistry – A European Journal |language=en |volume=27 |issue=54 |pages=13624–13631 |doi=10.1002/chem.202102035 |pmid=34245056 |issn=0947-6539|url-access=subscription }}</ref> The first empirically isolated polyoxorhenate was the white [Re<sub>4</sub>O<sub>15</sub>]<sup>2−</sup> and contained Re(VII) in both octahedral and tetrahedral coordination.<ref>{{Cite journal |last1=Volkov |first1=Mikhail A. |last2=Novikov |first2=Anton P. |last3=Borisova |first3=Nataliya E. |last4=Grigoriev |first4=Mikhail S. |last5=German |first5=Konstantin E. |date=2023-08-21 |title=Intramolecular Re···O Nonvalent Interactions as a Stabilizer of the Polyoxorhenate(VII) |url=https://pubs.acs.org/doi/10.1021/acs.inorgchem.3c01863 |journal=Inorganic Chemistry |language=en |volume=62 |issue=33 |pages=13485–13494 |doi=10.1021/acs.inorgchem.3c01863 |pmid=37599582 |issn=0020-1669|url-access=subscription }}</ref>

== History ==

=== Manganese ===
Manganese dioxide, which is abundant in nature, has long been used as a pigment. The cave paintings in [[Gargas, Haute-Garonne|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 [[Middle Ages]] until modern times and is evident in 14th-century glass from [[Venice]].<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>

=== Technetium and rhenium ===

Rhenium ({{langx|la|Rhenus}} meaning: "[[Rhine]]")<ref>{{cite book|language=de|title=Forschen Suche und Sucht|first=Hans Georg|last=Tilgner|publisher=Books on Demand| date=2000|isbn=978-3-89811-272-7|url=https://books.google.com/books?id=UWBWnMOGtMQC}}</ref> was the last-discovered of the elements that have a stable isotope (other new elements discovered in nature since then, such as [[francium]], are radioactive).<ref name="usgs">{{cite web|publisher=[[United States Geological Survey]]|url=http://minerals.usgs.gov/minerals/pubs/commodity/rhenium/|work=Minerals Information|title=Rhenium: Statistics and Information|date=2011|access-date=2011-05-25}}</ref> The existence of a yet-undiscovered element at this position in the [[periodic table]] had been first predicted by [[Dmitri Mendeleev]]. Other calculated information was obtained by [[Henry Moseley]] in 1914.<ref>{{cite journal|first=Henry|last=Moseley|title=The High-Frequency Spectra of the Elements, Part II|doi=10.1080/14786440408635141|journal=Philosophical Magazine|date=1914|pages=703–713|volume=27|issue=160|url=http://www.chemistry.co.nz/henry_moseley_article.htm|access-date=2009-05-14|archive-url=https://web.archive.org/web/20100122022821/http://www.materials.manchester.ac.uk/research/facilities/moseley/biography/|archive-date=2010-01-22}}</ref> In 1908, [[Japan]]ese chemist [[Masataka Ogawa]] announced that he had discovered the 43rd element and named it ''nipponium'' (Np) after [[Japan]] (''Nippon'' in Japanese). In fact, what he had was rhenium (element 75), not [[technetium]].<ref>{{cite journal|doi=10.1016/j.sab.2003.12.027|title=Discovery of a new element 'nipponiumʼ: re-evaluation of pioneering works of Masataka Ogawa and his son Eijiro Ogawa|date=2004|last=Yoshihara|first=H. K.|journal=Spectrochimica Acta Part B: Atomic Spectroscopy|volume=59|pages=1305–1310|bibcode=2004AcSpB..59.1305Y|issue=8}}</ref><ref name=nipponium2022>{{cite journal |last1=Hisamatsu |first1=Yoji |last2=Egashira |first2=Kazuhiro |first3=Yoshiteru |last3=Maeno |date=2022 |title=Ogawa's nipponium and its re-assignment to rhenium |journal=Foundations of Chemistry |volume=24 |issue= |pages=15–57 |doi=10.1007/s10698-021-09410-x |doi-access=free }}</ref> The symbol Np was later used for the element [[neptunium]], and the name "nihonium", also [[Names of Japan#Nihon and Nippon|named after Japan]], along with symbol Nh, was later used for [[nihonium|element 113]]. Element 113 was also discovered by a team of Japanese scientists and was named in respectful homage to Ogawa's work.<ref>{{cite journal |last1=Öhrström |first1=Lars |last2=Reedijk |first2=Jan |date=28 November 2016 |title=Names and symbols of the elements with atomic numbers 113, 115, 117 and 118 (IUPAC Recommendations 2016) |url=https://www.degruyter.com/downloadpdf/j/pac.2016.88.issue-12/pac-2016-0501/pac-2016-0501.pdf |journal=Pure Appl. Chem. |volume=88 |issue=12 |pages=1225–1229 |doi=10.1515/pac-2016-0501 |access-date=22 April 2017|hdl=1887/47427 |s2cid=99429711 |hdl-access=free }}</ref>

Rhenium was rediscovered by [[Walter Noddack]], [[Ida Tacke|Ida Noddack]], and [[Otto Berg (scientist)|Otto Berg]] in [[Germany]]. In 1925 they reported that they had detected the element in platinum ore and in the mineral [[columbite]]. They also found rhenium in [[gadolinite]] and [[molybdenite]].<ref name="'Ekamangane'">{{cite journal|last=Noddack|first=W.|author2=Tacke, I. |author3=Berg, O. |title=Die Ekamangane| journal=Naturwissenschaften| date=1925|volume=13|issue=26 |pages=567–574|doi=10.1007/BF01558746 |bibcode=1925NW.....13..567.|s2cid=32974087}}</ref> In 1928 they were able to extract 1 g of the element by processing 660&nbsp;kg of molybdenite.<ref name="1g">{{cite journal|last=Noddack| first=W.|author2=Noddack, I. |title=Die Herstellung von einem Gram Rhenium |journal=Zeitschrift für Anorganische und Allgemeine Chemie|date=1929|volume=183|issue=1|pages =353–375|doi=10.1002/zaac.19291830126|language=de}}</ref><!--The following text is a 1 to one copy from the USGS site: The process was so complicated and expensive that production was discontinued until early 1950 when tungsten-rhenium and molybdenum-rhenium alloys were prepared. These alloys found important applications in industry that resulted in a great demand for the rhenium produced from the molybdenite fraction of porphyry [[copper]] ores.{{citation needed|date = May 2012}}--> It was estimated in 1968 that 75% of the rhenium metal in the [[United States]] was used for research and the development of [[refractory metal]] alloys. It took several years from that point before the superalloys became widely used.<ref>{{cite book| pages =4–5| url =https://books.google.com/books?id=oD8rAAAAYAAJ&pg=PA4| title =Trends in usage of rhenium: Report| last1 =Committee On Technical Aspects Of Critical And Strategic Material| first1 =National Research Council (U.S.)| date =1968}}</ref><ref>{{cite book | url = https://books.google.com/books?id=Wd9GAAAAYAAJ | title = Rhenium alloys | last1 = Savitskiĭ | first1 = Evgeniĭ Mikhaĭlovich | last2 = Tulkina | first2 = Mariia Aronovna | last3 = Povarova | first3 = Kira Borisovna |author-link3=Kira Povarova | date = 1970}}</ref>

The [[Discovery of the chemical elements|discovery]] of element&nbsp;43 was finally confirmed in a 1937 experiment at the [[University of Palermo]] in Sicily by [[Carlo Perrier]] and [[Emilio Segrè]].<ref>{{cite book |last=Heiserman |first=D. L. |year=1992 |title=Exploring Chemical Elements and their Compounds |location=New York |publisher=TAB Books |isbn=978-0-8306-3018-9 |chapter=Element 43: Technetium |chapter-url=https://archive.org/details/exploringchemica01heis |page=164}}</ref> In mid-1936, Segrè visited the United States, first [[Columbia University]] in New York and then the [[Lawrence Berkeley National Laboratory]] in California. He persuaded [[cyclotron]] inventor [[Ernest Lawrence]] to let him take back some discarded cyclotron parts that had become [[radioactive]]. Lawrence mailed him a [[molybdenum]] foil that had been part of the deflector in the cyclotron.<ref>{{cite book |first=Emilio |last=Segrè |date=1993 |title=A Mind Always in Motion: The Autobiography of Emilio Segrè |publisher=University of California Press |location=Berkeley, California |isbn=978-0-520-07627-3 |pages=[https://archive.org/details/mindalwaysinmoti00segr/page/115 115–118] |url=https://archive.org/details/mindalwaysinmoti00segr/page/115 }}</ref>

=== Bohrium ===

Two groups claimed [[Timeline of chemical element discoveries|discovery of the element bohrium]]. Evidence of bohrium was first reported in 1976 by a Soviet research team led by [[Yuri Oganessian]], in which targets of [[bismuth-209]] and [[lead]]-208 were bombarded with accelerated nuclei of [[chromium]]-54 and [[manganese]]-55 respectively.<ref>{{cite journal|doi=10.1016/0375-9474(76)90607-2|title= On spontaneous fission of neutron-deficient isotopes of elements | volume=273|year=1976|journal=Nuclear Physics A|pages=505–522  | last1 = Yu | last2 = Demin | first2 = A.G. | last3 = Danilov | first3 = N.A. | last4 = Flerov | first4 = G.N. | last5 = Ivanov | first5 = M.P. | last6 = Iljinov | first6 = A.S. | last7 = Kolesnikov | first7 = N.N. | last8 = Markov | first8 = B.N. | last9 = Plotko | first9 = V.M. | last10 = Tretyakova | first10 = S.P.}}</ref> Two activities, one with a half-life of one to two milliseconds, and the other with an approximately five-second half-life, were seen. Since the ratio of the intensities of these two activities was constant throughout the experiment, it was proposed that the first was from the [[isotope]] bohrium-261 and that the second was from its daughter [[dubnium]]-257. Later, the dubnium isotope was corrected to dubnium-258, which indeed has a five-second half-life (dubnium-257 has a one-second half-life); however, the half-life observed for its parent is much shorter than the half-lives later observed in the definitive discovery of bohrium at [[Darmstadt]] in 1981. The [[International Union of Pure and Applied Chemistry|IUPAC]]/IUPAP Transfermium Working Group (TWG) concluded that while dubnium-258 was probably seen in this experiment, the evidence for the production of its parent bohrium-262 was not convincing enough.<ref name="93TWG" />

In 1981, a German research team led by [[Peter Armbruster]] and [[Gottfried Münzenberg]] at the [[GSI Helmholtz Centre for Heavy Ion Research]] (GSI Helmholtzzentrum für Schwerionenforschung) in Darmstadt bombarded a target of bismuth-209 with accelerated nuclei of chromium-54 to produce five atoms of the isotope bohrium-262:<ref name="262Bh">{{cite journal |last1=Münzenberg |first1=G. |last2=Hofmann |first2=S. |last3=Heßberger |first3=F. P. |last4=Reisdorf |first4=W. |last5=Schmidt |first5=K. H. |last6=Schneider |first6=J. H. R. |last7=Armbruster |first7=P. |last8=Sahm |first8=C. C. |last9=Thuma |first9=B. |year=1981 |title=Identification of element 107 by α correlation chains |journal=Zeitschrift für Physik A |volume=300 |issue=1 |pages=107–8 |doi=10.1007/BF01412623 |bibcode = 1981ZPhyA.300..107M |s2cid=118312056 |url=https://www.researchgate.net/publication/238901044 |access-date=24 December 2016 }}</ref>

:{{nuclide|link=yes|bismuth|209}} + {{nuclide|link=yes|chromium|54}} → {{nuclide|link=yes|bohrium|262}} + {{SubatomicParticle|link=yes|neutron}}

This discovery was further substantiated by their detailed measurements of the alpha decay chain of the produced bohrium atoms to previously known isotopes of [[fermium]] and [[californium]]. The [[International Union of Pure and Applied Chemistry|IUPAC]]/IUPAP Transfermium Working Group (TWG) recognised the GSI collaboration as official discoverers in their 1992 report.<ref name="93TWG">{{Cite journal |doi=10.1351/pac199365081757 |title=Discovery of the transfermium elements. Part II: Introduction to discovery profiles. Part III: Discovery profiles of the transfermium elements |year=1993 |author=Barber, R. C. |journal=Pure and Applied Chemistry |volume=65 |page=1757 |last2=Greenwood |first2=N. N. |last3=Hrynkiewicz |first3=A. Z. |last4=Jeannin |first4=Y. P. |last5=Lefort |first5=M. |last6=Sakai |first6=M. |last7=Ulehla |first7=I. |last8=Wapstra |first8=A. P. |last9=Wilkinson |first9=D. H. |issue=8|s2cid=195819585 |doi-access=free
}}</ref>

== Occurrence and production ==

=== Manganese ===
{{Main|Manganese#Production}}

Manganese comprises about 1000&nbsp;[[Parts per million|ppm]]&nbsp;(0.1%) of the [[Earth's crust]] and is the [[Abundance of elements in Earth's crust|12th most abundant element]].<ref name="Emsley2001">{{harvnb|Emsley|2001|pp=[https://archive.org/details/naturesbuildingb0000emsl/page/249 249–253]}}</ref> Soil contains 7–9000&nbsp;ppm of manganese with an average of 440&nbsp;ppm.<ref name="Emsley2001" /> The&nbsp;atmosphere contains 0.01&nbsp;μg/m<sup>3</sup>.<ref name="Emsley2001" /> Manganese occurs principally as [[pyrolusite]] ([[manganese(IV) oxide|MnO<sub>2</sub>]]), [[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> [[psilomelane]] {{chem2|(Ba,H2O)2Mn5O10}}, and to a lesser extent as [[rhodochrosite]] ([[manganese(II) carbonate|MnCO<sub>3</sub>]]).

[[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 ([[manganese(IV) oxide|MnO<sub>2</sub>]]). Other economically important manganese ores usually show a close spatial relation to the iron ores, such as [[sphalerite]].<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><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|url-access=subscription}}</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 billion tons of [[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 journal |title=Manganese Nodules: Dimensions and Perspectives |journal=Marine Geology |volume=41 |issue=3–4 |page=343|publisher=Springer |date=1978 |isbn=978-90-277-0500-6 |author=United Nations Ocean Economics and Technology Office, Technology Branch, United Nations |bibcode=1981MGeol..41..343C |doi=10.1016/0025-3227(81)90092-X}}</ref>

In South Africa, most identified deposits are located near [[Hotazel]] in the [[Northern Cape Province]], with a 2011 estimate of 15 billion tons. In 2011 South Africa produced 3.4 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.com |access-date=4 January 2014 |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>

For the production of [[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 to 80%.<ref name="Holl" /> Pure manganese used for the production of iron-free alloys is produced by [[Leaching (metallurgy)|leaching]] manganese ore with [[sulfuric acid]] and a subsequent [[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|left|thumb|upright=1.3|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 in a heap leach. 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 [[Mill (grinding)|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 [[Iron(II)|ferrous iron]] (Fe<sup>2+</sup>) in a 1.6:1 ratio. The iron reacts with the [[manganese dioxide]] (MnO<sub>2</sub>) to form [[iron(III) oxide-hydroxide]] (FeO(OH)) and elemental manganese (Mn):

This process yields approximately 92% recovery of the manganese. For further purification, the manganese can then be sent to an 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.|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 [[Central Intelligence Agency|CIA]]'s [[Project Azorian]], through billionaire [[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 [[Union of Soviet Socialist Republics|Soviet]] submarine, the [[Soviet submarine K-129 (1960)|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 nodule|Mn 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 |bibcode=2018JPPB..189..234H |s2cid=53248245 |url=https://www.sciencedirect.com/science/article/abs/pii/S101113441830959X |access-date=2 February 2021|url-access=subscription }}</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 |archive-date=23 October 2021 |archive-url=https://web.archive.org/web/20211023145629/https://isa.org.jm/files/files/documents/eng7.pdf }}</ref> are located along the [[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. Mn 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|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 [[United Nations]] affiliated bodies and state-sponsored companies in an attempt to fully understand [[environmental issues|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>

=== Technetium ===

{{Main|Technetium#Occurrence and Production}}
Technetium was created by bombarding [[molybdenum]] atoms with [[deuteron]]s that had been accelerated by a device called a [[cyclotron]]. Technetium occurs naturally in the Earth's [[Crust (geology)|crust]] in minute concentrations of about 0.003 parts per trillion. Technetium is so rare because the [[half-life|half-lives]] of <sup>97</sup>Tc and <sup>98</sup>Tc are only 4.2&nbsp;million&nbsp;years. More than a thousand of such periods have passed since the formation of the [[Earth]], so the probability of survival of even one atom of [[primordial nuclide|primordial]] technetium is effectively zero. However, small amounts exist as spontaneous [[fission product]]s in [[uranium ore]]s. A kilogram of uranium contains an estimated 1&nbsp;[[Orders of magnitude (mass)|nanogram]] (10<sup>−9</sup>&nbsp;g) equivalent to ten trillion atoms of technetium.<ref name="blocks">{{harvnb|Emsley|2001|pp=[https://archive.org/details/naturesbuildingb0000emsl/page/422 422]–425}}</ref><ref>{{cite journal|doi=10.1021/ac961159q |title=Analysis of Naturally Produced Technetium and Plutonium in Geologic Materials|date=1997 |last1=Dixon|first1=P.|last2=Curtis|first2=David B. |last3=Musgrave|first3=John |last4=Roensch|first4=Fred|last5=Roach|first5=Jeff|last6=Rokop|first6=Don|journal=Analytical Chemistry |volume=69|issue=9|pages=1692–1699|pmid=21639292}}</ref><ref>{{cite journal |doi=10.1016/S0016-7037(98)00282-8 |title=Nature's uncommon elements: plutonium and technetium|last1=Curtis|first1=D. |last2=Fabryka-Martin|first2=June|last3=Dixon|first3=Paul|last4=Cramer|first4=Jan|date=1999 |journal=Geochimica et Cosmochimica Acta |volume=63|issue=2|page=275|bibcode=1999GeCoA..63..275C |url=https://digital.library.unt.edu/ark:/67531/metadc704244/}}</ref> Some [[red giant]] stars with the spectral types S-, M-, and N contain a spectral absorption line indicating the presence of technetium.{{sfn|Hammond|2004|loc=[https://archive.org/details/crchandbookofche81lide/page/n905 p. 4-1]}}<ref>{{cite journal|doi=10.1126/science.114.2951.59|date=1951 |last1=Moore|first1=C. E.|title=Technetium in the Sun|journal=Science |volume=114 |issue=2951 |pages=59–61 |pmid=17782983|bibcode=1951Sci...114...59M}}</ref><!--Technetium in Red Giant Stars P Merrill&nbsp;— Science, 1952--> These red giants are known informally as [[technetium star]]s.

=== Rhenium ===
{{Main|Rhenium#Production}}

[[Image:Molybdenit 1.jpg|thumb|left|Molybdenite]]
Rhenium is one of the rarest elements in [[Earth's crust]] with an average concentration of 1&nbsp;ppb;<ref name="G&W" /><ref name=":1">{{Cite web|url=https://www.rsc.org/periodic-table/element/75/rhenium|title=Rhenium - Element information, properties and uses {{!}} Periodic Table|website=www.rsc.org|access-date=2019-12-02}}</ref> other sources quote the number of 0.5&nbsp;ppb making it the 77th most abundant element in Earth's crust.{{sfn|Emsley|2001|pp=[https://archive.org/details/naturesbuildingb0000emsl/page/358 358–360]}} Rhenium is probably not found free in nature (its possible natural occurrence is uncertain), but occurs in amounts up to 0.2%<ref name="G&W" /> in the mineral [[molybdenite]] (which is primarily [[molybdenum disulfide]]), the major commercial source, although single molybdenite samples with up to 1.88% have been found.<ref name="Rousch" /> [[Chile]] has the world's largest rhenium reserves, part of the copper ore deposits, and was the leading producer as of 2005.<ref>{{cite web|url=http://minerals.usgs.gov/minerals/pubs/country/2005/cimyb05.pdf |first=Steve T.|last=Anderson| publisher=[[United States Geological Survey]]|title=2005 Minerals Yearbook: Chile|access-date=2008-10-26}}</ref> It was only recently that the first rhenium [[mineral]] was found and described (in 1994), a rhenium [[sulfide mineral]] (ReS<sub>2</sub>) condensing from a [[fumarole]] on [[Kudriavy]] volcano, [[Iturup]] island, in the [[Kuril Islands]].<ref>{{cite journal|last=Korzhinsky|first=M. A.|author2=Tkachenko, S. I. |author3=Shmulovich, K. I. |author4=Taran Y. A. |author5= Steinberg, G. S. | date=2004-05-05|title=Discovery of a pure rhenium mineral at Kudriavy volcano|journal=[[Nature (journal)|Nature]]|volume=369|pages=51–52|doi=10.1038/369051a0|issue=6475|bibcode = 1994Natur.369...51K |s2cid=4344624}}</ref> Kudriavy discharges up to 20–60&nbsp;kg rhenium per year mostly in the form of rhenium disulfide.<ref>{{cite journal| last1 = Kremenetsky| first1 = A. A.| last2 = Chaplygin| first2 = I. V.| title = Concentration of rhenium and other rare metals in gases of the Kudryavy Volcano (Iturup Island, Kurile Islands)| journal = Doklady Earth Sciences| volume = 430| issue = 1| page = 114| date = 2010| doi = 10.1134/S1028334X10010253|bibcode = 2010DokES.430..114K | s2cid = 140632604}}</ref><ref>{{cite journal | last1 = Tessalina | first1 = S. | last2 = Yudovskaya | first2 = M. | last3 = Chaplygin | first3 = I. | last4 = Birck | first4 = J. | last5 = Capmas | first5 = F. | title = Sources of unique rhenium enrichment in fumaroles and sulphides at Kudryavy volcano | journal = Geochimica et Cosmochimica Acta | volume = 72 | page = 889 | date = 2008 | doi = 10.1016/j.gca.2007.11.015 | bibcode=2008GeCoA..72..889T | issue = 3}}</ref> Named [[rheniite]], this rare mineral commands high prices among collectors.<ref>{{cite web|url=http://www.galleries.com/minerals/sulfides/rheniite/rheniite.htm|publisher=Amethyst Galleries|title=The Mineral Rheniite}}</ref> <!--Dr. Kremenetsky from [[Russian Academy of Sciences|RAS]] Mineralogy Institute argues that this source could be commercially exploited,<ref>[http://www.nkj.ru/archive/articles/5340/ Завод на вулкане] // Наука и жизнь, № 11, 2000, in Russian.</ref> but currently there is no active attempts to extract it.-->

[[Image:Ammonium perrhenate.jpg|thumb|right|Ammonium perrhenate]]

Most of the rhenium extracted comes from [[Porphyry (geology)|porphyry]] [[molybdenum]] deposits.<ref>{{cite book|chapter=Chapter 7: By-Products of Porphyry Copper and Molybdenum Deposits|first1=D. A.|last1=John|first2=R. D.|last2=Taylor|title=Rare earth and critical elements in ore deposits|year=2016|volume=18|pages=137–164|doi=10.5382/Rev.18.07 |url=https://pubs.er.usgs.gov/publication/70048652|editor=Philip L. Verplanck and Murray W. Hitzman}}</ref> These ores typically contain 0.001% to 0.2% rhenium.<ref name="G&W"/> Roasting the ore volatilizes rhenium oxides.<ref name="Rousch">{{cite journal|doi = 10.1021/cr60291a002|title = Recent advances in the chemistry of rhenium|date = 1974|author = Rouschias, George|journal = Chemical Reviews|volume = 74|page = 531|issue = 5}}</ref> [[Rhenium(VII) oxide]] and [[perrhenic acid]] readily dissolve in water; they are leached from flue dusts and gasses and extracted by precipitating with [[potassium chloride|potassium]] or [[ammonium chloride]] as the [[perrhenate]] salts, and purified by [[Recrystallization (chemistry)|recrystallization]].<ref name="G&W" /> Total world production is between 40 and 50 tons/year; the main producers are in Chile, the United States, Peru, and Poland.<ref name="USGS_2012_summary">{{cite web|title=Rhenium|work=Mineral Commodity Summaries |publisher=U.S. Geological Survey|date=January 2012|url=http://minerals.usgs.gov/minerals/pubs/commodity/rhenium/mcs-2012-rheni.pdf|first=Michael J.|last=Magyar|access-date=2013-09-04}}</ref> Recycling of used Pt-Re catalyst and special alloys allow the recovery of another 10 tons per year. Prices for the metal rose rapidly in early 2008, from $1000–$2000 per [[kilogram|kg]] in 2003–2006 to over $10,000 in February 2008.<ref name="minormetals">{{cite web|title=MinorMetal prices|publisher=minormetals.com|url=http://www.minormetals.com/|access-date=2008-02-17|archive-date=2008-05-15|archive-url=https://web.archive.org/web/20080515180506/http://www.minormetals.com/}}</ref><ref>{{cite web|url=http://in.reuters.com/article/oilRpt/idINL1037587920080710|first=Jan|last=Harvey|title=Analysis: Super hot metal rhenium may reach "platinum prices"|date=2008-07-10|access-date=2008-10-26|publisher=Reuters India|archive-date=2009-01-11|archive-url=https://web.archive.org/web/20090111183605/http://in.reuters.com/article/oilRpt/idINL1037587920080710}}</ref> The metal form is prepared by reducing [[ammonium perrhenate]] with [[hydrogen]] at high temperatures:<ref name="Brauer" />

:2 NH<sub>4</sub>ReO<sub>4</sub> + 7 H<sub>2</sub> → 2 Re + 8 H<sub>2</sub>O + 2 NH<sub>3</sub>
:There are technologies for the associated extraction of rhenium from productive solutions of underground leaching of uranium ores.<ref>{{Cite journal |last1=Rudenko |first1=A.A. |last2=Troshkina |first2=I.D. |last3=Danileyko |first3=V.V. |last4=Barabanov |first4=O.S. |last5=Vatsura |first5=F.Y. |title=Prospects for selective-and-advanced recovery of rhenium from pregnant solutions of in-situ leaching of uranium ores at Dobrovolnoye deposit |url=https://mst.misis.ru/jour/article/view/287 |journal=Gornye Nauki i Tekhnologii = Mining Science and Technology (Russia) |year=2021 |volume=6 |issue=3 |pages=158–169|doi=10.17073/2500-0632-2021-3-158-169 |s2cid=241476783 |url-access=subscription }}</ref>

=== Bohrium ===

Bohrium is a synthetic element that does not occur in nature. Very few atoms have been synthesized, and also due to its radioactivity, only limited research has been conducted. Bohrium is only produced in nuclear reactors and has never been isolated in pure form.

== Applications ==

[[File:Fac-MbpyCO3X.png|thumb|Structure of the facial isomer of M(R-bpy)(CO)<sub>3</sub>X where M = Mn, Re; X = Cl, Br; R-bpy = 4,4'-disubstituted-2,2'-bipyridine]]
The [[Octahedral molecular geometry|''facial'' isomer]] of both rhenium and manganese 2,2'-bipyridyl tricarbonyl halide complexes have been extensively researched as catalysts for [[Electrochemical reduction of carbon dioxide|electrochemical carbon dioxide reduction]] due to their high selectivity and stability. They are commonly abbreviated as M(R-bpy)(CO)<sub>3</sub>X where M = Mn, Re; R-bpy = 4,4'-disubstituted [[2,2′-Bipyridine|2,2'-bipyridine]]; and X = Cl, Br.

=== Manganese ===

The rarity of rhenium has shifted research toward the manganese version of these catalysts as a more sustainable alternative.<ref name=":2" /> The first reports of catalytic activity of Mn(R-bpy)(CO)<sub>3</sub>Br towards CO<sub>2</sub> reduction came from Chardon-Noblat and coworkers in 2011.<ref>{{Cite journal|last=Bourrez|first=Marc|date=2011|title=[Mn(bipyridyl)(CO)3Br]: an abundant metal carbonyl complex as efficient electrocatalyst for CO2 reduction|journal=Angewandte Chemie International Edition in English |volume=50|issue=42 |pages=9903–9906|doi=10.1002/anie.201103616 |pmid=21922614 }}</ref> Compared to Re analogs, Mn(R-bpy)(CO)<sub>3</sub>Br shows catalytic activity at lower overpotentials.<ref name=":3" />

The catalytic mechanism for Mn(R-bpy)(CO)<sub>3</sub>X is complex and depends on the steric profile of the bipyridine ligand. When R is not bulky, the catalyst dimerizes to form [Mn(R-bpy)(CO)<sub>3</sub>]<sub>2</sub> before forming the active species. When R is bulky, however, the complex forms the active species without dimerizing, reducing the overpotential of CO<sub>2</sub> reduction by 200-300 mV. Unlike Re(R-bpy)(CO)<sub>3</sub>X, Mn(R-bpy)(CO)<sub>3</sub>X only reduces CO<sub>2</sub> in the presence of an acid.<ref name=":3" />

=== Technetium ===

[[File:Basedow-vor-nach-RIT.jpg|thumb|upright|Technetium [[Nuclear medicine|scintigraphy]] of a neck of [[Graves' disease]] patient|alt=Upper image: two drop-like features merged at their bottoms; they have a yellow centre and a red rim on a black background. Caption: Graves' Disease Tc-Uptake 16%. Lower image: red dots on black background. Caption: 250 Gy (30mCi) + Prednison.]]

[[Technetium-99m]] ("m" indicates that this is a [[Nuclear isomer#Metastable isomers|metastable]] nuclear isomer) is used in radioactive isotope [[nuclear medicine|medical tests]]. For example, Technetium-99m is a [[radioactive tracer]] that medical imaging equipment tracks in the human body.<ref name="blocks" /><ref name="bbc-20150530">{{cite news |url=https://www.bbc.co.uk/news/magazine-32833599 |title=The element that can make bones glow |author=Laurence Knight |publisher=BBC |date=30 May 2015 |access-date=30 May 2015}}</ref><ref>{{cite journal|display-authors=4|author=Guérin B|author2=Tremblay S|author3=Rodrigue S|author4=Rousseau JA |author5=Dumulon-Perreault V|author6=Lecomte R|author7=van Lier JE|author8=Zyuzin A|author9=van Lier EJ |title=Cyclotron production of <sup>99m</sup>Tc: an approach to the medical isotope crisis|journal=Journal of Nuclear Medicine |date=2010|volume=51|issue=4|pages=13N–6N|pmid=20351346 |url=http://jnm.snmjournals.org/content/51/4/13N.full.pdf}}</ref> It is well suited to the role because it emits readily detectable 140&nbsp;[[Electronvolt|keV]] [[gamma ray]]s, and its half-life is 6.01&nbsp;hours (meaning that about 94% of it decays to technetium-99 in 24&nbsp;hours).<ref name="enc">{{cite book| title=The Encyclopedia of the Chemical Elements| editor=Hampel, C. A.| last=Rimshaw |first=S. J.| location=New York| publisher=Reinhold Book Corporation| date=1968| url=https://archive.org/details/encyclopediaofch00hamp| url-access=registration| pages=[https://archive.org/details/encyclopediaofch00hamp/page/689 689–693]}}</ref> The chemistry of technetium allows it to be bound to a variety of biochemical compounds, each of which determines how it is metabolized and deposited in the body, and this single isotope can be used for a multitude of diagnostic tests. More than 50 common [[radiopharmaceuticals]] are based on technetium-99m for imaging and functional studies of the [[Human brain|brain]], heart muscle, [[thyroid]], [[Human lung|lungs]], [[liver]], [[gall bladder]], [[kidney]]s, [[Human skeleton|skeleton]], [[blood]], and [[tumor]]s.{{sfn|Schwochau|2000|p=414}} Technetium-99m is also used in radioimaging.<ref>{{cite book|first1=Roger |last1=Alberto|first2=Qaisar|last2=Nadeem|title=Metal Ions in Bio-Imaging Techniques|publisher=Springer|year=2021|pages=195–238|chapter=Chapter 7. <sup>99m</sup> Technetium-Based Imaging Agents and Developments in <sup>99</sup>Tc Chemistry|doi=10.1515/9783110685701-013|s2cid=233684677}}</ref>

The longer-lived isotope, technetium-95m with a half-life of 61&nbsp;days, is used as a [[radioactive tracer]] to study the movement of technetium in the environment and in plant and animal systems.{{sfn|Schwochau|2000|pp=12–27}}

Technetium-99 decays almost entirely by beta decay, emitting beta particles with consistent low energies and no accompanying gamma rays. Moreover, its long half-life means that this emission decreases very slowly with time. It can also be extracted to a high chemical and isotopic purity from radioactive waste. For these reasons, it is a [[National Institute of Standards and Technology]] (NIST) standard beta emitter, and is used for equipment calibration.{{sfn|Schwochau|2000|p=87}} Technetium-99 has also been proposed for optoelectronic devices and [[nanotechnology|nanoscale]] [[nuclear battery|nuclear batteries]].<ref>{{cite report|date = 2006-11-30|title = University Research Program in Robotics REPORT|publisher = University of Florida|url = http://www.osti.gov/bridge/servlets/purl/895620-n4Nt3U/895620.PDF|access-date = 2007-10-12|doi = 10.2172/895620|author1 = James S. Tulenko|author2 = Dean Schoenfeld |author3 = David Hintenlang|author4 = Carl Crane|author5 = Shannon Ridgeway|author6 = Jose Santiago|author7 = Charles Scheer}}</ref>

Like [[rhenium]] and [[palladium]], technetium can serve as a [[catalyst]]. In processes such as the [[dehydrogenation]] of [[isopropyl alcohol]], it is a far more effective catalyst than either rhenium or palladium. However, its radioactivity is a major problem in safe catalytic applications.{{sfn|Schwochau|2000|pp=87–90}}

When steel is immersed in water, adding a small concentration (55&nbsp;[[parts per notation|ppm]]) of potassium pertechnetate(VII) to the water protects the [[steel]] from corrosion, even if the temperature is raised to {{convert|250|C|K|abbr=on}}.{{sfn|Emsley|2001|p=425}} For this reason, pertechnetate has been used as an anodic [[corrosion]] inhibitor for steel, although technetium's radioactivity poses problems that limit this application to self-contained systems.<ref>{{cite book|chapter=Ch. 14 Separation Techniques |date=July 2004 |title=EPA: 402-b-04-001b-14-final |publisher=US Environmental Protection Agency |chapter-url=https://www.epa.gov/sites/default/files/2015-05/documents/402-b-04-001b-14-final.pdf |archive-url=https://web.archive.org/web/20140308042639/http://www.epa.gov/radiation/docs/marlap/402-b-04-001b-14-final.pdf |archive-date=2014-03-08 |url-status=live |access-date=2008-08-04}}</ref> While (for example) {{chem|CrO|4|2-}} can also inhibit corrosion, it requires a concentration ten times as high. In one experiment, a specimen of carbon steel was kept in an aqueous solution of pertechnetate for 20&nbsp;years and was still uncorroded.{{sfn|Emsley|2001|p=425}} The mechanism by which pertechnetate prevents corrosion is not well understood, but seems to involve the reversible formation of a thin surface layer ([[Passivation (chemistry)|passivation]]). One theory holds that the pertechnetate reacts with the steel surface to form a layer of technetium [[oxide|dioxide]] which prevents further corrosion; the same effect explains how iron powder can be used to remove pertechnetate from water. The effect disappears rapidly if the concentration of pertechnetate falls below the minimum concentration or if too high a concentration of other ions is added.{{sfn|Schwochau|2000|p=91}}

As noted, the radioactive nature of technetium (3&nbsp;MBq/L at the concentrations required) makes this corrosion protection impractical in almost all situations. Nevertheless, corrosion protection by pertechnetate ions was proposed (but never adopted) for use in [[boiling water reactor]]s.{{sfn|Schwochau|2000|p=91}}

=== Rhenium ===

The catalytic activity of Re(bpy)(CO)<sub>3</sub>Cl for carbon dioxide reduction was first studied by Lehn et al.<ref>{{Cite journal|last=Hawecker|first=Jeannot|date=1984|title=Electrocatalytic Reduction of Carbon Dioxide Mediated by Re(bipy)(CO)3Cl (bipy = 2,2'-bipyridine)|journal=J. Chem. Soc., Chem. Commun.|pages=328–330|doi=10.1039/C39840000328 }}</ref> and Meyer et al.<ref>{{Cite journal|last=Sullivan|first=B. Patrick|date=1985|title=One- and Two-electron Pathways in the Electrocatalytic Reduction of CO2 by fac-Re(bpy)(CO)3Cl (bpy = 2,2'-bipyridine)|journal=J. Chem. Soc., Chem. Commun.|pages=1414–1416|doi=10.1039/C39850001414 }}</ref> in 1984 and 1985, respectively. Re(R-bpy)(CO)<sub>3</sub>X complexes exclusively produce CO from CO<sub>2</sub> reduction with [[Faraday efficiency|Faradaic efficiencies]] of close to 100% even in solutions with high concentrations of water or [[Brønsted–Lowry acid–base theory|Brønsted acids]].<ref name=":2">{{Cite journal|last=Grice|first=Kyle|date=2014|title=Recent Studies of Rhenium and Manganese Bipyridine Carbonyl Catalysts for the Electrochemical Reduction of CO2|journal=Advances in Inorganic Chemistry|volume=66|pages=163–188|doi=10.1016/B978-0-12-420221-4.00005-6 |isbn=978-0-12-420221-4 }}</ref>

The catalytic mechanism of Re(R-bpy)(CO)<sub>3</sub>X involves reduction of the complex twice and loss of the X ligand to generate a five-coordinate active species which binds CO<sub>2</sub>. These complexes will reduce CO<sub>2</sub> both with and without an additional acid present; however, the presence of an acid increases catalytic activity.<ref name=":2" /> The high selectivity of these complexes to CO<sub>2</sub> reduction over the competing [[Water splitting|hydrogen evolution reaction]] has been shown by [[density functional theory]] studies to be related to the faster kinetics of CO<sub>2</sub> binding compared to H<sup>+</sup> binding.<ref name=":3">{{Cite journal|last=Francke|first=Robert|date=2018|title=Homogeneously Catalyzed Electroreduction of Carbon Dioxide -- Methods, Mechanisms, and Catalysts|journal=Chemical Reviews|volume=118|issue=9 |pages=4631–4701|doi=10.1021/acs.chemrev.7b00459 |pmid=29319300 }}</ref>

=== Bohrium ===

Bohrium is a synthetic element and is too radioactive to be used in anything.

== Toxicity and precautions ==

Manganese compounds are less toxic than those of other widespread metals, such as [[nickel]] and [[copper]].<ref>{{cite book|page=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 |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 poisoning has been linked to impaired motor skills and cognitive disorders.<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>

Technetium has low chemical toxicity. For example, no significant change in blood formula, body and organ weights, and food consumption could be detected for rats which ingested up to 15&nbsp;μg of technetium-99 per gram of food for several weeks.<ref>{{cite book|url=https://books.google.com/books?id=QLHr-UYWoo8C&pg=PA392|pages=392–395|title=Technetium in the environment|author=Desmet, G.|author2=Myttenaere, C.|publisher=Springer|isbn=978-0-85334-421-6|date=1986}}</ref> In the body, technetium quickly gets converted to the stable {{chem|TcO|4|-}} ion, which is highly water-soluble and quickly excreted. The radiological toxicity of technetium (per unit of mass) is a function of compound, type of radiation for the isotope in question, and the isotope's half-life.{{sfn|Schwochau|2000|pp=371–381}} However, it is radioactive, so all isotopes must be handled carefully. The primary hazard when working with technetium is inhalation of dust; such [[radioactive contamination]] in the lungs can pose a significant cancer risk. For most work, careful handling in a [[fume hood]] is sufficient, and a [[glove box]] is not needed.{{sfn|Schwochau|2000|p=40}}

Very little is known about the toxicity of rhenium and its compounds because they are used in very small amounts. Soluble salts, such as the rhenium halides or perrhenates, could be hazardous due to elements other than rhenium or due to rhenium itself.{{sfn|Emsley|2001|p=358-361}} Only a few compounds of rhenium have been tested for their acute toxicity; two examples are potassium perrhenate and rhenium trichloride, which were injected as a solution into rats. The perrhenate had an [[Median lethal dose|LD<sub>50</sub>]] value of 2800&nbsp;mg/kg after seven days (this is very low toxicity, similar to that of table salt) and the rhenium trichloride showed LD<sub>50</sub> of 280&nbsp;mg/kg.<ref>{{cite journal|title=Pharmacology and toxicology of potassium perrhenate and rhenium trichloride|pages=321–323|first =Thomas J.|last=Haley|author2=Cartwright, Frank D. |doi=10.1002/jps.2600570218|journal=Journal of Pharmaceutical Sciences|volume=57|issue=2|date=1968|pmid=5641681}}</ref>

== Biological role ==

{{Main|Manganese in biology}}

Of the group 7 elements, only manganese has a role in the human body. It is an essential trace nutrient, with the body containing approximately 10 [[milligram]]s at any given time. It is present as a [[coenzyme]] in biological processes that include macronutrient metabolism, bone formation, and [[free radical]] defense systems. It is a critical component in dozens of proteins and enzymes.<ref name=":4">{{cite book |doi=10.1515/9783110527872-016 |chapter=Manganese: Its Role in Disease and Health |title=Essential Metals in Medicine: Therapeutic Use and Toxicity of Metal Ions in the Clinic |year=2019 |pages=253–266 |pmid=30855111 |isbn=978-3-11-052787-2 |last1=Erikson |first1=K. M. |last2=Aschner |first2=M. |series=Metal Ions in Life Sciences |volume=19 |publisher=[[De Gruyter]] |s2cid=73725546 }}</ref> The manganese in the human body is mainly concentrated in the bones, and the soft tissue remainder is concentrated in the liver and kidneys.{{sfn|Emsley|2001|pp=[https://archive.org/details/naturesbuildingb0000emsl/page/249 249–253]}} In the human brain, the manganese is bound to manganese [[metalloprotein]]s, most notably [[glutamine synthetase]] in [[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> Technetium, rhenium, and bohrium have no known biological roles. Technetium is, however, used in radioimaging.

== References ==
<references>
<ref name="Brauer">{{cite book |author=O. Glemser |chapter=Rhenium |title=Handbook of Preparative Inorganic Chemistry |edition=2nd |editor=G. Brauer |publisher=Academic Press |year=1963 |volume=1 |pages=1476–1485}}</ref>

<ref name="Haire">{{cite book |title=The Chemistry of the Actinide and Transactinide Elements |editor1-last=Morss |editor2-first=Norman M. |editor2-last=Edelstein |editor3-last=Fuger |editor3-first=Jean |last1=Hoffman|first1=Darleane C. |last2=Lee |first2=Diana M. |last3=Pershina |first3=Valeria |chapter=Transactinides and the future elements |publisher=[[Springer Science+Business Media]] |year=2006 |isbn=1-4020-3555-1 |location=Dordrecht, The Netherlands |edition=3rd |ref=CITEREFHaire2006}}</ref>
</references>

===Bibliography===
* {{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|url=https://archive.org/details/naturesbuildingb0000emsl}}
* {{cite book |editor-last1=Lide |editor-first1=David R. |title=CRC handbook of chemistry and physics: a ready-reference book of chemical and physical data |date=2004 |publisher=Boca Raton : CRC Press |isbn=978-0-8493-0485-9 |url=https://archive.org/details/crchandbookofche81lide/page/n905 |last=Hammond |first=C. R.}}
* {{cite book|url=https://books.google.com/books?id=BHjxH8q9iukC&pg=PP1|last=Schwochau |first=K. |year=2000 |title=Technetium: Chemistry and Radiopharmaceutical Applications |place=Weinheim, Germany |publisher=Wiley-VCH |isbn=978-3-527-29496-1}}

{{Periodic table (navbox)}}
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{{Group 7 elements}}

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[[Category:Groups (periodic table)]]