Editing Roentgenium

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{{Infobox roentgenium}}

'''Roentgenium''' ({{IPA|de|ʁœntˈɡeːni̯ʊm|lang|De-Roentgenium.ogg}}) is a [[synthetic element|synthetic chemical element]]; it has [[Chemical symbol|symbol]] '''Rg''' and [[atomic number]] 111. It is extremely radioactive and can only be created in a laboratory. The most stable known isotope, roentgenium-282, has a [[half-life]] of 130 seconds, although the unconfirmed roentgenium-286 may have a longer half-life of about 10.7&nbsp;minutes. Roentgenium was first created in December 1994 by the [[GSI Helmholtz Centre for Heavy Ion Research]] near [[Darmstadt]], Germany. It is named after the physicist [[Wilhelm Röntgen]] ([[Ö#O-umlaut|also spelled]] Roentgen), who discovered [[X-ray]]s. Only a few roentgenium atoms have ever been synthesized, and they have no practical application.

In the [[periodic table]], it is a [[d-block]] [[transactinide element]]. It is a member of the [[period 7 element|7th period]] and is placed in the [[group 11 element]]s, although no chemical experiments have been carried out to confirm that it behaves as the heavier [[Homologous series|homologue]] to [[gold]] in group 11 as the ninth member of the 6d series of [[transition metal]]s. Roentgenium is calculated to have similar properties to its lighter homologues, [[copper]], [[silver]], and gold, although it may show some differences from them.

==Introduction==
{{Excerpt|Superheavy element|Introduction|subsections=yes}}

==History==
[[File:Roentgen2.jpg|thumb|right|upright|Roentgenium was named after the physicist [[Wilhelm Röntgen]], the discoverer of [[X-ray]]s.]]
===Official discovery===
Roentgenium was [[discovery of the chemical elements|first synthesized]] by an international team led by [[Sigurd Hofmann]] at the [[Gesellschaft für Schwerionenforschung]] (GSI) in [[Darmstadt]], [[Germany]], on December 8, 1994.<ref name="95Ho01">{{cite journal|doi=10.1007/BF01291182|title=The new element 111|year=1995|author=Hofmann, S.|journal=Zeitschrift für Physik A|volume=350|pages=281–282|last2=Ninov|first2=V.|last3=Heßberger|first3=F.P.|last4=Armbruster|first4=P.|last5=Folger|first5=H.|last6=Münzenberg|first6=G.|last7=Schött|first7=H. J.|last8=Popeko|first8=A. G.|last9=Yeremin|first9=A. V.|first10=A. N.|last10=Andreyev|first11=S.|last11=Saro|first12=R.|last12=Janik|first13=M.|last13=Leino|bibcode=1995ZPhyA.350..281H|issue=4|s2cid=18804192}}</ref> The team bombarded a target of [[bismuth-209]] with accelerated nuclei of [[nickel]]-64 and detected three nuclei of the [[isotope]] <sup>272</sup>111:

:{{nuclide|link=yes|Bismuth|209}} + {{nuclide|link=yes|Nickel|64}} → <sup>272</sup>111 + {{SubatomicParticle|link=yes|10neutron}}

This reaction had previously been conducted at the [[JINR|Joint Institute for Nuclear Research]] in [[Dubna]] (then in the [[Soviet Union]]) in 1986, but no atoms of <sup>272</sup>111 had then been observed.<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|pages=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}} (Note: for Part I see Pure Appl. Chem., Vol. 63, No. 6, pp. 879–886, 1991)</ref> In 2001, the [[IUPAC/IUPAP Joint Working Party]] (JWP) concluded that there was insufficient evidence for the discovery at that time.<ref>{{Cite journal|url=http://iupac.org/publications/pac/2001/pdf/7306x0959.pdf|title=On the discovery of the elements 110–112|author=Karol|journal=Pure Appl. Chem.|volume=73|issue=6|pages=959–967|date=2001|doi=10.1351/pac200173060959|last2=Nakahara|first2=H.|last3=Petley|first3=B. W.|last4=Vogt|first4=E.|s2cid=97615948|access-date=March 11, 2008|archive-date=March 9, 2018|archive-url=https://web.archive.org/web/20180309212208/https://www.iupac.org/publications/pac/2001/pdf/7306x0959.pdf|url-status=live}}</ref> The GSI team repeated their experiment in 2002 and detected three more atoms.<ref name="02Ho01">{{cite journal|last1=Hofmann|first1=S.|last2=Heßberger|first2=F. P.|last3=Ackermann|first3=D.|last4=Münzenberg|first4=G.|last5=Antalic|first5=S.|last6=Cagarda|first6=P.|last7=Kindler|first7=B.|last8=Kojouharova|first8=J.|last9=Leino|first9=M.|last10=Lommel|first10=B.|last11=Mann|first11=R.|last12=Popeko|first12=A. G.|last13=Reshitko|first13=S.|last14=Śaro|first14=S.|last15=Uusitalo|first15=J.|last16=Yeremin|first16=A. V.|title=New results on elements 111 and 112|date=2002|journal=European Physical Journal A|volume=14|issue=2|pages=147–157|doi=10.1140/epja/i2001-10119-x|bibcode=2002EPJA...14..147H|s2cid=8773326}}</ref><ref>{{Cite news|url=https://repository.gsi.de/record/53531/files/GSI-Report-2001-1.pdf|title=New results on element 111 and 112|author=Hofmann|display-authors=etal|publisher=GSI report 2000|pages=1–2|access-date=2018-04-21|archive-date=May 8, 2020|archive-url=https://web.archive.org/web/20200508221142/https://repository.gsi.de/record/53531/files/GSI-Report-2001-1.pdf|url-status=live}}</ref> In their 2003 report, the JWP decided that the GSI team should be acknowledged for the discovery of this element.<ref>{{Cite journal|url=http://iupac.org/publications/pac/2003/pdf/7510x1601.pdf|title=On the claims for discovery of elements 110, 111, 112, 114, 116, and 118|journal=Pure Appl. Chem.|volume=75|issue=10|pages=1601–1611|date=2003|doi=10.1351/pac200375101601|last1=Karol|first1=P. J.|last2=Nakahara|first2=H.|last3=Petley|first3=B. W.|last4=Vogt|first4=E.|s2cid=95920517|access-date=March 11, 2008|archive-date=August 22, 2016|archive-url=https://web.archive.org/web/20160822073903/https://www.iupac.org/publications/pac/2003/pdf/7510x1601.pdf|url-status=live}}</ref>

[[File:Backdrop for presentation of Röntgenium, element 111, at GSI Darmstadt.JPG|thumbnail|left|Backdrop for presentation of the discovery and recognition of roentgenium at GSI Darmstadt]]

===Naming===
Using [[Mendeleev's predicted elements|Mendeleev's nomenclature for unnamed and undiscovered elements]], roentgenium should be known as ''eka-[[gold]]''. In 1979, IUPAC published recommendations according to which the element was to be called ''unununium'' (with the corresponding symbol of ''Uuu''),<ref name="iupac">{{cite journal|author=Chatt, J.|journal=Pure and Applied Chemistry|date=1979|volume=51|pages=381–384|title=Recommendations for the naming of elements of atomic numbers greater than 100|doi=10.1351/pac197951020381|issue=2|doi-access=free}}</ref> a [[systematic element name]] as a [[placeholder name|placeholder]], until the element was discovered (and the discovery then confirmed) and a permanent name was decided on. Although widely used in the chemical community on all levels, from chemistry classrooms to advanced textbooks, the recommendations were mostly ignored among scientists in the field, who called it ''element 111'', with the symbol of ''E111'', ''(111)'' or even simply ''111''.<ref name="Haire" />

The name ''roentgenium'' (Rg) was suggested by the GSI team<ref name="IUPAC-Rg" /> in 2004, to honor the German physicist [[Wilhelm Conrad Röntgen]], the discoverer of [[X-ray]]s.<ref name="IUPAC-Rg">{{Cite journal|url=http://iupac.org/publications/pac/2004/pdf/7612x2101.pdf|title=Name and symbol of the element with atomic number 111|author=Corish|journal=Pure Appl. Chem.|date=2004|volume=76|issue=12|pages=2101–2103|doi=10.1351/pac200476122101|last2=Rosenblatt|first2=G. M.|s2cid=195819587|access-date=March 11, 2008|archive-date=August 9, 2017|archive-url=https://web.archive.org/web/20170809142907/https://www.iupac.org/publications/pac/2004/pdf/7612x2101.pdf|url-status=live}}</ref> This name was accepted by [[IUPAC]] on November 1, 2004.<ref name="IUPAC-Rg" />

==Isotopes==
{{Main|Isotopes of roentgenium}}
{{Isotopes summary
|element=roentgenium
|reaction ref=<ref name=thoennessen2016>{{Thoennessen2016|pages=229, 234, 238}}</ref>
|isotopes=
{{isotopes summary/isotope
|mn=272 |sym=Rg |hl={{sort|4|4.2 ms}} |ref={{NUBASE2020|ref}}
|dm=α |year=1994 |re=<sup>209</sup>Bi(<sup>64</sup>Ni,n)
}}
{{isotopes summary/isotope
|mn=274 |sym=Rg |hl={{sort|20|20 ms}} |ref={{NUBASE2020|ref}}
|dm=α |year=2004 |re=<sup>278</sup>Nh(—,α)
}}
{{isotopes summary/isotope
|mn=278 |sym=Rg |hl={{sort|5|4.6 ms}} |ref=<ref name=Mc2022>{{Cite journal |title=New isotope <sup>286</sup>Mc produced in the <sup>243</sup>Am+<sup>48</sup>Ca reaction |last1=Oganessian |first1=Yu. Ts. |last2=Utyonkov |first2=V. K. |last3=Kovrizhnykh |first3=N. D. |display-authors=et al. |date=2022 |journal=Physical Review C |volume=106 |number=64306 |page=064306 |doi=10.1103/PhysRevC.106.064306|bibcode=2022PhRvC.106f4306O |s2cid=254435744 |doi-access=free }}</ref>
|dm=α |year=2006 |re=<sup>282</sup>Nh(—,α)
}}
{{isotopes summary/isotope
|mn=279 |sym=Rg |hl={{sort|90|90 ms}} |ref=<ref name=Mc2022/>
|dm=α, SF |year=2003 |re=<sup>287</sup>Mc(—,2α)
}}
{{isotopes summary/isotope
|mn=280 |sym=Rg |hl={{sort|3900|3.9 s}} |ref=<ref name=Mc2022/>
|dm=α, EC |year=2003 |re=<sup>288</sup>Mc(—,2α)
}}
{{isotopes summary/isotope
|mn=281 |sym=Rg |hl={{sort|11000|11 s}} |ref=<ref name=Mc2022/>
|dm=SF, α |year=2010 |re=<sup>293</sup>Ts(—,3α)
}}
{{isotopes summary/isotope
|mn=282 |sym=Rg |hl={{sort|130000|130 s}} |ref={{NUBASE2020|ref}}
|dm=α |year=2010 |re=<sup>294</sup>Ts(—,3α)
}}
{{isotopes summary/isotope
|mn=283 |sym=Rg{{efn|name=nc|This isotope is unconfirmed}} |hl={{sort|306000|5.1 min}}
 |ref=<ref name="Hofmann2016-EXON-Remarks"/>
|dm=SF |year=1999 |re=<sup>283</sup>Cn(e<sup>−</sup>,ν<sub>e</sub>)
}}
{{isotopes summary/isotope
|mn=286 |sym=Rg{{efn|name=nc}} |hl={{sort|640000|10.7 min}} |ref=<ref name="Hofmann2016-EXON-Remarks">{{cite conference |title=Remarks on the Fission Barriers of SHN and Search for Element 120 |first1=S. |last1=Hofmann |first2=S. |last2=Heinz |first3=R. |last3=Mann |first4=J. |last4=Maurer |first5=G. |last5=Münzenberg |first6=S. |last6=Antalic |first7=W. |last7=Barth |first8=H. G. |last8=Burkhard |first9=L. |last9=Dahl |first10=K. |last10=Eberhardt |first11=R. |last11=Grzywacz |first12=J. H. |last12=Hamilton |first13=R. A. |last13=Henderson |first14=J. M. |last14=Kenneally |first15=B. |last15=Kindler |first16=I. |last16=Kojouharov |first17=R. |last17=Lang |first18=B. |last18=Lommel |first19=K. |last19=Miernik |first20=D. |last20=Miller |first21=K. J. |last21=Moody |first22=K. |last22=Morita |first23=K. |last23=Nishio |first24=A. G. |last24=Popeko |first25=J. B. |last25=Roberto |first26=J. |last26=Runke |first27=K. P. |last27=Rykaczewski |first28=S. |last28=Saro |first29=C. |last29=Schneidenberger |first30=H. J. |last30=Schött |first31=D. A. |last31=Shaughnessy |first32=M. A. |last32=Stoyer |first33=P. |last33=Thörle-Pospiech |first34=K. |last34=Tinschert |first35=N. |last35=Trautmann |first36=J. |last36=Uusitalo |first37=A. V. |last37=Yeremin |year=2016 |conference=Exotic Nuclei |editor1-first=Yu. E. |editor1-last=Peninozhkevich |editor2-first=Yu. G. |editor2-last=Sobolev |display-authors=3 |book-title=Exotic Nuclei: EXON-2016 Proceedings of the International Symposium on Exotic Nuclei |pages=155–164 |isbn=9789813226555 |doi=10.1142/9789813226548_0024 }}</ref><!-- exact copy/paste from infobox roentgenium isotopes, ref name="Hofmann2016-EXON-Remarks" 15 Jan 2023 -->
|dm=α |year=1998 |re=<sup>290</sup>Fl(e<sup>−</sup>,ν<sub>e</sub>α)
}}}}

Roentgenium has no stable or naturally occurring isotopes. Several radioactive isotopes have been synthesized in the laboratory, either by fusion of the nuclei of lighter elements or as intermediate decay products of heavier elements. Nine different isotopes of roentgenium have been reported with atomic masses 272, 274, 278–283, and 286 (283 and 286 unconfirmed), two of which, roentgenium-272 and roentgenium-274, have known but unconfirmed [[metastable state]]s. All of these decay through alpha decay or spontaneous fission,<ref name="nuclidetable">{{cite web|url=http://www.nndc.bnl.gov/chart/reCenter.jsp?z=111&n=170|title=Interactive Chart of Nuclides|publisher=Brookhaven National Laboratory|author=Sonzogni, Alejandro|location=National Nuclear Data Center|access-date=2008-06-06|archive-date=July 28, 2018|archive-url=https://www.webcitation.org/71Fx6kbAd?url=http://www.nndc.bnl.gov/chart/reCenter.jsp?z=111|url-status=dead}}</ref> though <sup>280</sup>Rg may also have an [[electron capture]] branch.<ref name="xxx">{{cite journal |last=Forsberg |first=U. |display-authors=et al.<!--53 co-authors omitted--> |title=Recoil-α-fission and recoil-α-α-fission events observed in the reaction <sup>48</sup>Ca + <sup>243</sup>Am |date=2016 |journal=[[Nuclear Physics A]] |volume=953 |pages=117–138 |doi=10.1016/j.nuclphysa.2016.04.025 |arxiv=1502.03030|bibcode=2016NuPhA.953..117F |s2cid=55598355 }}</ref>

===Stability and half-lives===
All roentgenium isotopes are extremely unstable and radioactive; in general, the heavier isotopes are more stable than the lighter. The most stable known roentgenium isotope, <sup>282</sup>Rg, is also the heaviest known roentgenium isotope; it has a half-life of 100&nbsp;seconds. The unconfirmed <sup>286</sup>Rg is even heavier and appears to have an even longer half-life of about 10.7&nbsp;minutes, which would make it one of the longest-lived superheavy nuclides known; likewise, the unconfirmed <sup>283</sup>Rg appears to have a long half-life of about 5.1&nbsp;minutes. The isotopes <sup>280</sup>Rg and <sup>281</sup>Rg have also been reported to have half-lives over a second. The remaining isotopes have half-lives in the millisecond range.<ref name="nuclidetable" />

The missing isotopes between <sup>274</sup>Rg and <sup>278</sup>Rg are too light to be produced by hot fusion and too heavy to be produced by cold fusion. A possible synthesis method is to populate them from above, as daughters of nihonium or moscovium isotopes that can be produced by hot fusion.{{sfn|Zagrebaev|Karpov|Greiner|2013|pp=1–15}} The isotopes <sup>283</sup>Rg and <sup>284</sup>Rg could be synthesised using charged-particle evaporation, using the <sup>238</sup>U+<sup>48</sup>Ca reaction where a proton is evaporated alongside some neutrons.<ref name=Yerevan2023PPT>{{cite conference |url=https://indico.jinr.ru/event/3622/contributions/20021/attachments/15292/25806/Yerevan2023.pdf |title=Interesting fusion reactions in superheavy region |first1=J. |last1=Hong |first2=G. G. |last2=Adamian |first3=N. V. |last3=Antonenko |first4=P. |last4=Jachimowicz |first5=M. |last5=Kowal |conference=IUPAP Conference "Heaviest nuclei and atoms" |publisher=Joint Institute for Nuclear Research |date=26 April 2023 |access-date=30 July 2023}}</ref><ref name=pxn>{{cite journal |last1=Hong |first1=J. |last2=Adamian |first2=G. G. |last3=Antonenko |first3=N. V. |date=2017 |title=Ways to produce new superheavy isotopes with ''Z''&nbsp;=&nbsp;111–117 in charged particle evaporation channels |journal=Physics Letters B |volume=764 |pages=42–48 |doi=10.1016/j.physletb.2016.11.002 |bibcode=2017PhLB..764...42H|doi-access=free }}</ref>

==Predicted properties==
Other than nuclear properties, no properties of roentgenium or its compounds have been measured; this is due to its extremely limited and expensive production<ref name="Superheavy element Bloomberg"/> and the fact that roentgenium (and its parents) decays very quickly. Properties of roentgenium metal remain unknown and only predictions are available.

===Chemical===
Roentgenium is the ninth member of the 6d series of [[transition metals]].<ref name="DoiX">{{cite journal|doi=10.1595/147106708X297486|title=The Periodic Table and the Platinum Group Metals|date=2008|last1=Griffith|first1=W. P.|journal=Platinum Metals Review|volume=52|issue=2|pages=114–119|doi-access=free}}</ref> Calculations on its [[ionization potential]]s and [[atomic radius|atomic]] and [[ionic radius|ionic radii]] are similar to that of its lighter homologue [[gold]], thus implying that roentgenium's basic properties will resemble those of the other [[group 11 element]]s, [[copper]], [[silver]], and gold; however, it is also predicted to show several differences from its lighter homologues.<ref name="Haire" />

Roentgenium is predicted to be a [[noble metal]]. The [[standard electrode potential]] of 1.9&nbsp;V for the Rg<sup>3+</sup>/Rg couple is greater than that of 1.5&nbsp;V for the Au<sup>3+</sup>/Au couple. Roentgenium's predicted first ionisation energy of 1020&nbsp;kJ/mol almost matches that of the [[noble gas]] [[radon]] at 1037&nbsp;kJ/mol.<ref name="Haire" /> Its predicted second ionization energy, 2070&nbsp;kJ/mol, is almost the same as that of silver. Based on the most stable oxidation states of the lighter group 11 elements, roentgenium is predicted to show stable +5 and +3 oxidation states, with a less stable +1 state. The +3 state is predicted to be the most stable. Roentgenium(III) is expected to be of comparable reactivity to gold(III), but should be more stable and form a larger variety of compounds. Gold also forms a somewhat stable −1 state due to relativistic effects, and it has been suggested roentgenium may do so as well:<ref name="Haire" /> nevertheless, the [[electron affinity]] of roentgenium is expected to be around {{convert|1.6|eVpar|abbr=on|lk=on}}, significantly lower than gold's value of {{convert|2.3|eVpar|abbr=on}}, so roentgenides may not be stable or even possible.{{Fricke1975}}
[[File:Electron_shell_111_roentgenium.png|thumb|Diagram of a roentgenium atom with [[electron shells]].]]
The 6d orbitals are destabilized by [[relativistic quantum chemistry|relativistic effects]] and [[spin–orbit interaction]]s near the end of the fourth transition metal series, thus making the high oxidation state roentgenium(V) more stable than its lighter homologue gold(V) (known only in [[gold pentafluoride]], Au<sub>2</sub>F<sub>10</sub>) as the 6d electrons participate in bonding to a greater extent. The spin-orbit interactions stabilize molecular roentgenium compounds with more bonding 6d electrons; for example, {{chem|RgF|6|-}} is expected to be more stable than {{chem|RgF|4|-}}, which is expected to be more stable than {{chem|RgF|2|-}}.<ref name="Haire" /> The stability of {{chem|RgF|6|-}} is homologous to that of {{chem|AuF|6|-}}; the silver analogue {{chem|AgF|6|-}} is unknown and is expected to be only marginally stable to decomposition to {{chem|AgF|4|-}} and F<sub>2</sub>. Moreover, Rg<sub>2</sub>F<sub>10</sub> is expected to be stable to decomposition, exactly analogous to the Au<sub>2</sub>F<sub>10</sub>, whereas Ag<sub>2</sub>F<sub>10</sub> should be unstable to decomposition to Ag<sub>2</sub>F<sub>6</sub> and F<sub>2</sub>. [[Gold heptafluoride]], AuF<sub>7</sub>, is known as a gold(V) difluorine complex AuF<sub>5</sub>·F<sub>2</sub>, which is lower in energy than a true gold(VII) heptafluoride would be; RgF<sub>7</sub> is instead calculated to be more stable as a true roentgenium(VII) heptafluoride, although it would be somewhat unstable, its decomposition to Rg<sub>2</sub>F<sub>10</sub> and F<sub>2</sub> releasing a small amount of energy at room temperature.<ref name=hepta>{{cite journal |last1=Conradie |first1=Jeanet |last2=Ghosh |first2=Abhik |date=15 June 2019 |title=Theoretical Search for the Highest Valence States of the Coinage Metals: Roentgenium Heptafluoride May Exist |journal=Inorganic Chemistry |volume=2019 |issue=58 |pages=8735–8738 |doi=10.1021/acs.inorgchem.9b01139|pmid=31203606 |s2cid=189944098 }}</ref> Roentgenium(I) is expected to be difficult to obtain.<ref name="Haire" /><ref>{{cite journal|last1=Seth |first1=M. |last2=Cooke |first2=F. |last3=Schwerdtfeger |first3=P. |last4=Heully |first4=J.-L. |last5=Pelissier |first5=M. |date=1998 |journal=J. Chem. Phys. |volume=109 |pages=3935–43 |doi=10.1063/1.476993 |title=The chemistry of the superheavy elements. II. The stability of high oxidation states in group 11 elements: Relativistic coupled cluster calculations for the di-, tetra- and hexafluoro metallates of Cu, Ag, Au, and element 111 |issue=10|bibcode = 1998JChPh.109.3935S|s2cid=54803557 |hdl=2292/5208 |hdl-access=free }}</ref><ref>{{cite journal |last1=Seth |first1=M. |last2=Faegri |first2=K. |last3=Schwerdtfeger |first3=P. |date=1998 |journal=Angew. Chem. Int. Ed. Engl. |volume=37 |pages=2493–6 |doi=10.1002/(SICI)1521-3773(19981002)37:18<2493::AID-ANIE2493>3.0.CO;2-F |title=The Stability of the Oxidation State +4 in Group 14 Compounds from Carbon to Element 114 |issue=18|pmid=29711350 }}</ref> Gold readily forms the [[cyanide]] [[coordination complex|complex]] {{chem|Au(CN)|2|-}}, which is used in its extraction from ore through the process of [[gold cyanidation]]; roentgenium is expected to follow suit and form {{chem|Rg(CN)|2|-}}.<ref>{{cite journal |last1=Demissie |first1=Taye B. |last2=Ruud |first2=Kenneth |date=25 February 2017 |title=Darmstadtium, roentgenium, and copernicium form strong bonds with cyanide |journal=International Journal of Quantum Chemistry |volume=2017 |pages=e25393 |doi=10.1002/qua.25393 |url=https://munin.uit.no/bitstream/10037/13632/4/article.pdf |hdl=10037/13632 |hdl-access=free |access-date=August 29, 2019 |archive-date=October 9, 2022 |archive-url=https://ghostarchive.org/archive/20221009/https://munin.uit.no/bitstream/10037/13632/4/article.pdf |url-status=live }}</ref>

The probable chemistry of roentgenium has received more interest than that of the two previous elements, [[meitnerium]] and [[darmstadtium]], as the valence s-[[Electron shell#Subshells|subshells]] of the group 11 elements are expected to be relativistically contracted most strongly at roentgenium.<ref name="Haire" /> Calculations on the molecular compound Rg[[hydrogen|H]] show that relativistic effects double the strength of the roentgenium–hydrogen bond, even though spin–orbit interactions also weaken it by {{convert|0.7|eVpar|abbr=on}}. The compounds [[gold|Au]]X and RgX, where X = [[fluorine|F]], [[chlorine|Cl]], [[bromine|Br]], [[oxygen|O]], Au, or Rg, were also studied.<ref name="Haire" /><ref>{{cite journal|last1=Liu |first1=W. |last2=van Wüllen |first2=C. |date=1999 |journal=J. Chem. Phys. |volume=110 |pages=3730–5 |doi=10.1063/1.478237 |title=Spectroscopic constants of gold and eka-gold (element 111) diatomic compounds: The importance of spin–orbit coupling |issue=8|bibcode = 1999JChPh.110.3730L}}</ref> Rg<sup>+</sup> is predicted to be the [[HSAB theory|softest]] metal ion, even softer than Au<sup>+</sup>, although there is disagreement on whether it would behave as an [[acid]] or a [[base (chemistry)|base]].<ref name="Thayer">{{cite book |last1=Thayer |first1=John S. |title=Relativistic Methods for Chemists |chapter=Relativistic Effects and the Chemistry of the Heavier Main Group Elements |date=2010 |page=82 |doi=10.1007/978-1-4020-9975-5_2 |volume=10 |isbn=978-1-4020-9974-8 |series=Challenges and Advances in Computational Chemistry and Physics }}</ref><ref name="Hancock">{{cite journal |last1=Hancock |first1=Robert D. |last2=Bartolotti |first2=Libero J. |last3=Kaltsoyannis |first3=Nikolas |date=24 November 2006 |title=Density Functional Theory-Based Prediction of Some Aqueous-Phase Chemistry of Superheavy Element 111. Roentgenium(I) Is the 'Softest' Metal Ion |journal=Inorg. Chem. |volume=45 |issue=26 |pages=10780–5 |doi=10.1021/ic061282s|pmid=17173436 }}</ref> In aqueous solution, Rg<sup>+</sup> would form the [[aqua ion]] [Rg(H<sub>2</sub>O)<sub>2</sub>]<sup>+</sup>, with an Rg–O bond distance of 207.1&nbsp;[[picometer|pm]]. It is also expected to form Rg(I) complexes with [[ammonia]], [[phosphine]], and [[hydrogen sulfide]].<ref name="Hancock" />

===Physical and atomic===
Roentgenium is expected to be a solid under normal conditions and to crystallize in the [[body-centered cubic]] structure, unlike its lighter [[congener (chemistry)|congeners]] which crystallize in the [[face-centered cubic]] structure, due to its being expected to have different electron charge densities from them.<ref name="bcc" /> It should be a very heavy metal with a [[density]] of around 22–24&nbsp;g/cm<sup>3</sup>; in comparison, the densest known element that has had its density measured, [[osmium]], has a density of 22.61&nbsp;g/cm<sup>3</sup>.<ref name="density" /><ref name="kratz" /> The atomic radius of roentgenium is expected to be around 114&nbsp;pm.<ref name="Darleane"/>

==Experimental chemistry==
Unambiguous determination of the chemical characteristics of roentgenium has yet to have been established<ref name="Düllmann">{{cite journal |last1=Düllmann |first1=Christoph E. |date=2012 |title=Superheavy elements at GSI: a broad research program with element 114 in the focus of physics and chemistry |journal=Radiochimica Acta |volume=100 |issue=2 |pages=67–74 |doi=10.1524/ract.2011.1842 |s2cid=100778491 }}</ref> due to the low yields of reactions that produce roentgenium isotopes.<ref name="Haire" /> For chemical studies to be carried out on a [[transactinide element|transactinide]], at least four atoms must be produced, the half-life of the isotope used must be at least 1&nbsp;second, and the rate of production must be at least one atom per week.<ref name="DoiX" /> Even though the half-life of <sup>282</sup>Rg, the most stable confirmed roentgenium isotope, is 100&nbsp;seconds, long enough to perform chemical studies, another obstacle is the need to increase the rate of production of roentgenium isotopes and allow experiments to carry on for weeks or months so that statistically significant results can be obtained. Separation and detection must be carried out continuously to separate out the roentgenium isotopes and allow automated systems to experiment on the gas-phase and solution chemistry of roentgenium, as the yields for heavier elements are predicted to be smaller than those for lighter elements. However, the experimental chemistry of roentgenium has not received as much attention as that of the heavier elements from [[copernicium]] to [[livermorium]],<ref name="Haire" /><ref name="Düllmann" /><ref name="Eichler">{{cite journal |last=Eichler |first=Robert |date=2013 |title=First foot prints of chemistry on the shore of the Island of Superheavy Elements |journal=Journal of Physics: Conference Series |volume=420 |issue=1 |doi=10.1088/1742-6596/420/1/012003 |pages=012003|arxiv=1212.4292 |bibcode=2013JPhCS.420a2003E |s2cid=55653705 }}</ref> despite early interest in theoretical predictions due to relativistic effects on the ''n''s subshell in group 11 reaching a maximum at roentgenium.<ref name="Haire" /> The isotopes <sup>280</sup>Rg and <sup>281</sup>Rg are promising for chemical experimentation and may be produced as the granddaughters of the [[moscovium]] isotopes <sup>288</sup>Mc and <sup>289</sup>Mc respectively;<ref name="Moody">{{cite book |chapter=Synthesis of Superheavy Elements |last1=Moody |first1=Ken |editor1-first=Matthias |editor1-last=Schädel |editor2-first=Dawn |editor2-last=Shaughnessy |title=The Chemistry of Superheavy Elements |publisher=Springer Science & Business Media |edition=2nd |pages=24–8 |isbn=9783642374661|date=2013-11-30 }}</ref> their parents are the [[nihonium]] isotopes <sup>284</sup>Nh and <sup>285</sup>Nh, which have already received preliminary chemical investigations.<ref name="Superheavy element Aksenov"/>

==See also==
* [[Island of stability]]

== Explanatory notes ==
{{notelist}}

== References ==
{{Reflist|30em|refs=

}}

== General bibliography ==
* {{cite journal |ref={{harvid|Audi et al.|2017}} |title=The NUBASE2016 evaluation of nuclear properties |doi=10.1088/1674-1137/41/3/030001 |last1=Audi |first1=G. |last2=Kondev |first2=F. G. |last3=Wang |first3=M. |last4=Huang |first4=W. J. |last5=Naimi |first5=S. |display-authors=3 |journal=Chinese Physics C |volume=41 |issue=3 <!--Citation bot deny-->|pages=030001 |year=2017 
|bibcode=2017ChPhC..41c0001A }}<!--for consistency and specific pages, do not replace with {{NUBASE2016}}-->
* {{cite book|last=Beiser|first=A.|title=Concepts of modern physics|date=2003|publisher=McGraw-Hill|isbn=978-0-07-244848-1|edition=6th|oclc=48965418}}
* {{cite book |last1=Hoffman |first1=D. C. |author-link=Darleane C. Hoffman |last2=Ghiorso |first2=A. |author-link2=Albert Ghiorso |last3=Seaborg |first3=G. T. |title=The Transuranium People: The Inside Story |year=2000 |publisher=[[World Scientific]] |isbn=978-1-78-326244-1}}
* {{cite book |last=Kragh |first=H. |author-link=Helge Kragh |date=2018 |title=From Transuranic to Superheavy Elements: A Story of Dispute and Creation |publisher=[[Springer Science+Business Media|Springer]] |isbn=978-3-319-75813-8 }}
* {{cite journal|last1=Zagrebaev|first1=V.|last2=Karpov|first2=A.|last3=Greiner|first3=W.|date=2013|title=Future of superheavy element research: Which nuclei could be synthesized within the next few years?|journal=[[Journal of Physics: Conference Series]]|volume=420|issue=1|pages=012001|doi=10.1088/1742-6596/420/1/012001|arxiv=1207.5700|bibcode=2013JPhCS.420a2001Z|s2cid=55434734|issn=1742-6588}}

==External links==
{{Commons category}}
* [http://www.periodicvideos.com/videos/111.htm Roentgenium] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)

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