View source for Seaborgium

{{good article}}
{{infobox seaborgium}}
'''Seaborgium''' is a [[synthetic element|synthetic chemical element]]; it has [[Chemical symbol|symbol]] '''Sg''' and [[atomic number]] 106. It is named after the American [[nuclear chemist]] [[Glenn T. Seaborg]]. As a synthetic element, it can be created in a laboratory but is not found in nature. It is also [[radioactive]]; the most stable known [[isotope]], <sup>269</sup>Sg, has a [[half-life]] of approximately 14&nbsp;minutes.<ref name="PuCa2017" />

In the [[periodic table]] of the elements, it is a [[d-block]] [[transactinide element]]. It is a member of the [[period 7|7th period]] and belongs to the [[group 6 elements]] as the fourth member of the 6d series of [[transition metal]]s. Chemistry experiments have confirmed that seaborgium behaves as the heavier [[Homologous series|homologue]] to [[tungsten]] in group 6. The chemical properties of seaborgium are characterized only partly, but they compare well with the chemistry of the other group 6 elements.

In 1974, a few atoms of seaborgium were produced in laboratories in the [[Soviet Union]] and in the United States. The priority of the discovery and therefore the [[Transfermium Wars|naming of the element was disputed]] between Soviet and American scientists, and it was not until 1997 that the [[International Union of Pure and Applied Chemistry]] (IUPAC) established seaborgium as the official name for the element. It is one of only two elements named after a living person at the time of naming, the other being [[oganesson]], element 118.{{efn|The names [[einsteinium]] and [[fermium]] for elements 99 and 100 were proposed when their namesakes ([[Albert Einstein]] and [[Enrico Fermi]] respectively) were still alive, but were not made official until Einstein and Fermi had died.{{sfn|Hoffman|Ghiorso|Seaborg|2000|pp=187–189}}}}

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

==History==
Following claims of the observation of elements [[rutherfordium|104]] and [[dubnium|105]] in 1970 by [[Albert Ghiorso]] et al. at the [[Lawrence Livermore National Laboratory]], a search for element 106 using oxygen-18 projectiles and the previously used californium-249 target was conducted.<ref name="Transuraniumppl" /> Several 9.1 MeV [[alpha decay]]s were reported and are now thought to originate from element 106, though this was not confirmed at the time. In 1972, the HILAC accelerator received equipment upgrades, preventing the team from repeating the experiment, and data analysis was not done during the shutdown.<ref name="Transuraniumppl">{{cite book|last1=Hoffman|first1=D.C |last2=Ghiorso|first2=A.|last3=Seaborg|first3=G.T.|title=The Transuranium People: The Inside Story |publisher=Imperial College Press|date=2000|isbn=978-1-86094-087-3|pages=300–327}}</ref> This reaction was tried again several years later, in 1974, and the Berkeley team realized that their new data agreed with their 1971 data, to the astonishment of Ghiorso. Hence, element 106 could have actually been discovered in 1971 if the original data was analyzed more carefully.<ref name="Transuraniumppl" />

Two groups claimed [[discovery of the chemical elements|discovery of the element]]. Unambiguous evidence of element 106 was first reported in 1974 by a Russian research team in [[Dubna]] led by [[Yuri Oganessian]], in which targets of [[lead-208]] and [[lead-207]] were bombarded with accelerated ions of [[chromium-54]]. In total, fifty-one [[spontaneous fission]] events were observed with a half-life between four and ten [[milliseconds]]. After having ruled out nucleon [[Nuclear reaction#Transfer reactions|transfer reactions]] as a cause for these activities, the team concluded that the most likely cause of the activities was the spontaneous fission of isotopes of element 106. The isotope in question was first suggested to be seaborgium-259, but was later corrected to seaborgium-260.<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
|journal=Pure and Applied Chemistry
|volume=65
|pages=1757
|last1=Barber |first1=R. C.
|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>

:{{nuclide|link=yes|lead|208}} + {{nuclide|link=yes|chromium|54}} → {{nuclide|link=yes|seaborgium|260}} + 2 {{SubatomicParticle|link=yes|neutron}}
:{{nuclide|link=yes|lead|207}} + {{nuclide|chromium|54}} → {{nuclide|seaborgium|260}} + {{SubatomicParticle|neutron}}

A few months later in 1974, researchers including Glenn T. Seaborg, [[Carol Alonso]] and Albert Ghiorso at the [[University of California, Berkeley]], and E. Kenneth Hulet from the Lawrence Livermore National Laboratory, also synthesized the element<ref>{{cite journal|first1=A. |last1=Ghiorso |first2=J. M. |last2=Nitschke |first3=J. R. |last3=Alonso |first4=C. T. |last4=Alonso |first5=M. |last5=Nurmia |first6=G. T. |last6=Seaborg |first7=E. K. |last7=Hulet |first8=R. W. |last8=Lougheed |journal=Physical Review Letters |title=Element 106 |volume=33 |issue=25 |page=1490 |date=December 1974 |doi=10.1103/PhysRevLett.33.1490 |bibcode=1974PhRvL..33.1490G |doi-access=free }}</ref> by bombarding a [[californium]]-249 target with [[oxygen-18]] ions, using equipment similar to that which had been used for the synthesis of [[rutherfordium|element 104]] five years earlier, observing at least seventy [[alpha decay]]s, seemingly from the isotope seaborgium-263m with a half-life of {{val|0.9|0.2}} seconds. The alpha daughter rutherfordium-259 and granddaughter nobelium-255 had previously been synthesised and the properties observed here matched with those previously known, as did the intensity of their production. The [[cross-section (physics)|cross-section]] of the reaction observed, 0.3&nbsp;[[barn (unit)|nanobarns]], also agreed well with theoretical predictions. These bolstered the assignment of the alpha decay events to seaborgium-263m.<ref name="93TWG" />

:{{nuclide|link=yes|californium|249}} + {{nuclide|link=yes|oxygen|18}} → {{nuclide|link=yes|seaborgium|263m}} + 4 {{SubatomicParticle|link=yes|10neutron}} → {{nuclide|link=yes|rutherfordium|259}} + {{SubatomicParticle|link=yes|alpha}} → {{nuclide|link=yes|nobelium|255}} + {{SubatomicParticle|link=yes|alpha}}

A dispute thus arose from the initial competing claims of discovery, though unlike the case of the synthetic elements up to [[dubnium|element 105]], neither team of discoverers chose to announce proposed names for the new elements, thus averting an [[element naming controversy]] temporarily. The dispute on discovery, however, dragged on until 1992, when the IUPAC/IUPAP Transfermium Working Group (TWG), formed to put an end to the controversy by making conclusions regarding discovery claims for elements 101 to [[copernicium|112]], concluded that the Soviet synthesis of seaborgium-260 was not convincing enough, "lacking as it is in yield curves and angular selection results", whereas the American synthesis of seaborgium-263 was convincing due to its being firmly anchored to known daughter nuclei. As such, the TWG recognised the Berkeley team as official discoverers in their 1993 report.<ref name="93TWG" />

[[File:Seaborg in lab - restoration.jpg|thumb|upright=1.0|Element 106 was named after [[Glenn T. Seaborg]], a pioneer in the discovery of [[synthetic element]]s, with the name ''seaborgium'' (Sg).]]
[[File:Chemist Glenn Seaborg (14678590682).jpg|thumb|right|Seaborg pointing to the element named after him on the periodic table]]
Seaborg had previously suggested to the TWG that if Berkeley was recognised as the official discoverer of elements 104 and 105, they might propose the name ''kurchatovium'' (symbol Kt) for element 106 to honour the Dubna team, which had proposed this name for element 104 after [[Igor Kurchatov]], the former head of the [[Soviet nuclear research]] programme. However, due to the worsening relations between the competing teams after the publication of the TWG report (because the Berkeley team vehemently disagreed with the TWG's conclusions, especially regarding element 104), this proposal was dropped from consideration by the Berkeley team.<ref name="transuranium">Hoffman, D.C., Ghiorso, A., Seaborg, G. T. The Transuranium People: The Inside Story, (2000), 369–399</ref> After being recognized as official discoverers, the Berkeley team started deciding on a name in earnest:

{{blockquote|...we were given credit for the discovery and the accompanying right to name the new element. The eight members of the Ghiorso group suggested a wide range of names honoring Isaac Newton, Thomas Edison, Leonardo da Vinci, Ferdinand Magellan, the mythical Ulysses, George Washington, and Finland, the native land of a member of the team. There was no focus and no front-runner for a long period.<br>Then one day Al [Ghiorso] walked into my office and asked what I thought of naming element 106 "seaborgium." I was floored.<ref name="vanderkrogt">{{cite web|url=http://elements.vanderkrogt.net/element.php?sym=sg |title=106 Seaborgium |publisher=Elements.vanderkrogt.net |access-date=12 September 2008}}</ref>|author=Glenn Seaborg}}

Seaborg's son Eric remembered the naming process as follows:<ref name="EricSeaborg" />

{{blockquote|With eight scientists involved in the discovery suggesting so many good possibilities, Ghiorso despaired of reaching consensus, until he awoke one night with an idea. He approached the team members one by one, until seven of them had agreed. He then told his friend and colleague of 50 years: "We have seven votes in favor of naming element 106 seaborgium. Will you give your consent?" My father was flabbergasted, and, after consulting my mother, agreed.<ref name="EricSeaborg">{{cite journal|first = Seaborg|last = Eric|date = 2003 |title = Seaborgium|journal = Chemical and Engineering News|url = http://pubs.acs.org/cen/80th/seaborgium.html|volume = 81|issue = 36}}</ref>|author=Eric Seaborg}}

The name ''seaborgium'' and symbol ''Sg'' were announced at the 207th national meeting of the [[American Chemical Society]] in March 1994 by Kenneth Hulet, one of the co-discovers.<ref name="vanderkrogt" /> However, [[IUPAC]] resolved in August 1994 that an element could not be named after a living person, and Seaborg was still alive at the time. Thus, in September 1994, IUPAC recommended a set of names in which the names proposed by the three laboratories (the third being the [[GSI Helmholtz Centre for Heavy Ion Research]] in [[Darmstadt]], [[Germany]]) with competing claims to the discovery for elements 104 to [[meitnerium|109]] were shifted to various other elements, in which ''rutherfordium'' (Rf), the Berkeley proposal for element 104, was shifted to element 106, with ''seaborgium'' being dropped entirely as a name.<ref name="transuranium" />

<div style="float:center; margin:0; font-size:85%;">
{|class="wikitable"
|+ Summary of element naming proposals and final decisions for elements 101–112 (those covered in the TWG report)<ref name="transuranium" />
|-
! Atomic number !! Systematic !! American !! Russian !! German !! Compromise 92 !! IUPAC 94 !! ACS 94 !! IUPAC 95 !! IUPAC 97 !! Present
|-
| 101 || unnilunium || mendelevium || {{sdash}} || {{sdash}} || mendelevium || mendelevium || mendelevium || mendelevium || mendelevium || mendelevium
|-
| 102 || unnilbium || nobelium || joliotium || {{sdash}} || joliotium || nobelium || nobelium || flerovium || nobelium || nobelium
|-
| 103 || unniltrium || lawrencium || rutherfordium || {{sdash}} || lawrencium || lawrencium || lawrencium || lawrencium || lawrencium || lawrencium
|-
| 104 || unnilquadium || rutherfordium || kurchatovium || {{sdash}} || meitnerium || dubnium || rutherfordium || dubnium || rutherfordium || rutherfordium
|-
| 105 || unnilpentium || hahnium || nielsbohrium || {{sdash}} || kurchatovium || joliotium || hahnium || joliotium || dubnium || dubnium
|-
| 106 || unnilhexium || seaborgium || {{sdash}} || {{sdash}} || rutherfordium || rutherfordium || seaborgium || seaborgium || seaborgium || seaborgium
|-
| 107 || unnilseptium || {{sdash}} || {{sdash}} || nielsbohrium || nielsbohrium || bohrium || nielsbohrium || nielsbohrium || bohrium || bohrium
|-
| 108 || unniloctium || {{sdash}} || {{sdash}} || hassium || hassium || hahnium || hassium || hahnium || hassium || hassium
|-
| 109 || unnilennium || {{sdash}} || {{sdash}} || meitnerium || hahnium || meitnerium || meitnerium || meitnerium || meitnerium || meitnerium
|-
| 110 || ununnilium || hahnium || becquerelium || darmstadtium || {{sdash}} || {{sdash}} || {{sdash}} || {{sdash}} || {{sdash}} || darmstadtium
|-
| 111 || unununium || {{sdash}} || {{sdash}} || roentgenium || {{sdash}} || {{sdash}} || {{sdash}} || {{sdash}} || {{sdash}} || roentgenium
|-
| 112 || ununbium || {{sdash}} || {{sdash}} || copernicium || {{sdash}} || {{sdash}} || {{sdash}} || {{sdash}} || {{sdash}} || copernicium
|}
</div>

This decision ignited a firestorm of worldwide protest for disregarding the historic discoverer's right to name new elements, and against the new retroactive rule against naming elements after living persons; the American Chemical Society stood firmly behind the name ''seaborgium'' for element 106, together with all the other American and German naming proposals for elements 104 to 109, approving these names for its journals in defiance of IUPAC.<ref name="transuranium" /> At first, IUPAC defended itself, with an American member of its committee writing: "Discoverers don't have a right to name an element. They have a right to suggest a name. And, of course, we didn't infringe on that at all." However, Seaborg responded:

{{blockquote|This would be the first time in history that the acknowledged and uncontested discoverers of an element are denied the privilege of naming it.<ref name="vanderkrogt" />|author=Glenn Seaborg}}

Bowing to public pressure, IUPAC proposed a different compromise in August 1995, in which the name ''seaborgium'' was reinstated for element 106 in exchange for the removal of all but one of the other American proposals, which met an even worse response. Finally, IUPAC rescinded these previous compromises and made a final, new recommendation in August 1997, in which the American and German proposals for elements 104 to 109 were all adopted, including ''seaborgium'' for element 106, with the single exception of element 105, named ''dubnium'' to recognise the contributions of the Dubna team to the experimental procedures of transactinide synthesis. This list was finally accepted by the American Chemical Society, which wrote:<ref name="transuranium" />

{{blockquote|In the interest of international harmony, the Committee reluctantly accepted the name 'dubnium' for element 105 in place of 'hahnium' [the American proposal], which has had long-standing use in literature. We are pleased to note that 'seaborgium' is now the internationally approved name for element 106.<ref name="transuranium" />|author=American Chemical Society}}

Seaborg commented regarding the naming:

{{blockquote|I am, needless to say, proud that U.S. chemists recommended that element 106, which is placed under tungsten (74), be called 'seaborgium.' I was looking forward to the day when chemical investigators will refer to such compounds as seaborgous chloride, seaborgic nitrate, and perhaps, sodium seaborgate.<br>This is the greatest honor ever bestowed upon me—even better, I think, than winning the Nobel Prize.{{efn|Seaborg had in fact previously won the 1951 [[Nobel Prize in Chemistry]] together with [[Edwin McMillan]] for "their discoveries in the chemistry of the first transuranium elements".<ref name="Nobel Prize">{{cite web |title=The Nobel Prize in Chemistry 1951 |url=http://nobelprize.org/nobel_prizes/chemistry/laureates/1951/index.html |publisher=[[Nobel Foundation]] |access-date=August 26, 2012}}</ref>}} Future students of chemistry, in learning about the periodic table, may have reason to ask why the element was named for me, and thereby learn more about my work.<ref name="vanderkrogt" />|author=Glenn Seaborg}}

Seaborg died a year and a half later, on 25 February 1999, at the age of 86.<ref name="vanderkrogt" />

==Isotopes==
{{main|Isotopes of seaborgium}}
{{Isotopes summary
|element=seaborgium
|isotopes=
{{isotopes summary/isotope
|mn=258|sym=Sg|hl={{sort|3|2.7 ms}}|ref={{NUBASE2020|ref}}
|dm=SF |year=1994|re=<sup>209</sup>Bi(<sup>51</sup>V,2n)
}}
{{isotopes summary/isotope
|mn=259|sym=Sg|hl={{sort|402|402 ms}}|ref={{NUBASE2020|ref}}
|dm=α |year=1985|re=<sup>207</sup>Pb(<sup>54</sup>Cr,2n)
}}
{{isotopes summary/isotope
|mn=259m|sym=Sg|hl={{sort|226|226 ms}}|ref={{NUBASE2020|ref}}
|dm=α, SF |year=2015|re=<sup>206</sup>Pb(<sup>54</sup>Cr,n)<ref>{{cite journal |last1=Antalic |first1=S. |last2=Heßberger |first2=F. P. |last3=Ackermann |first3=D. |last4=Heinz |first4=S. |last5=Hofmann |first5=S. |last6=Kindler |first6=B. |last7=Khuyagbaatar |first7=J. |last8=Lommel |first8=B. |last9=Mann |first9=R. |title=Nuclear isomers in <sup>259</sup>Sg and <sup>255</sup>Rf |journal=The European Physical Journal A |date=14 April 2015 |volume=51 |issue=4 |pages=41 |doi=10.1140/epja/i2015-15041-0 |bibcode=2015EPJA...51...41A |s2cid=254117522 |url=https://link.springer.com/article/10.1140/epja/i2015-15041-0 |access-date=2 July 2023 |language=en |issn=1434-601X}}</ref>
}}
{{isotopes summary/isotope
|mn=260|sym=Sg|hl={{sort|5|4.95 ms}}|ref={{NUBASE2020|ref}}
|dm=SF, α |year=1985|re=<sup>208</sup>Pb(<sup>54</sup>Cr,2n)
}}
{{isotopes summary/isotope
|mn=261|sym=Sg|hl={{sort|183|183 ms}}|ref={{NUBASE2020|ref}}
|dm=α, β<sup>+</sup>, SF |year=1985|re=<sup>208</sup>Pb(<sup>54</sup>Cr,n)
}}
{{isotopes summary/isotope
|mn=261m|sym=Sg|hl={{sort|0|9.3 μs}}|ref={{NUBASE2020|ref}}
|dm=IT |year=2009|re=<sup>208</sup>Pb(<sup>54</sup>Cr,n)
}}
{{isotopes summary/isotope
|mn=262|sym=Sg|hl={{sort|10|10.3 ms}}|ref={{NUBASE2020|ref}}
|dm=SF, α |year=2001|re=<sup>270</sup>Ds(—,2α)
}}
{{isotopes summary/isotope
|mn=263|sym=Sg|hl={{sort|940|940 ms}}|ref={{NUBASE2020|ref}}
|dm=α, SF |year=1994|re=<sup>271</sup>Ds(—,2α)
}}
{{isotopes summary/isotope
|mn=263m|sym=Sg|hl={{sort|420|420 ms}}|ref={{NUBASE2020|ref}}
|dm=α |year=1974|re=<sup>249</sup>Cf(<sup>18</sup>O,4n)
}}
{{isotopes summary/isotope
|mn=264|sym=Sg|hl={{sort|78|78 ms}}|ref={{NUBASE2020|ref}}
|dm=SF |year=2006|re=<sup>238</sup>U(<sup>34</sup>Si,4n)
}}
{{isotopes summary/isotope
|mn=265|sym=Sg|hl={{sort|9200|9.2 s}}|ref={{NUBASE2020|ref}}
|dm=α |year=1993|re=<sup>248</sup>Cm(<sup>22</sup>Ne,5n)
}}
{{isotopes summary/isotope
|mn=265m|sym=Sg|hl={{sort|16400|16.4 s}}|ref={{NUBASE2020|ref}}
|dm=α |year=1993|re=<sup>248</sup>Cm(<sup>22</sup>Ne,5n)
}}
{{isotopes summary/isotope
|mn=266|sym=Sg|hl={{sort|390|390 ms}}|ref={{NUBASE2020|ref}}
|dm=SF |year=2004|re=<sup>270</sup>Hs(—,α)
}}
{{isotopes summary/isotope
|mn=267|sym=Sg|hl={{sort|590000|9.8 min}}|ref=<ref name=Ds2024>{{cite journal |last1=Oganessian |first1=Yu. Ts. |last2=Utyonkov |first2=V. K. |last3=Shumeiko |first3=M. V. |last4=Abdullin |first4=F. Sh. |last5=Adamian |first5=G. G. |last6=Dmitriev |first6=S. N. |last7=Ibadullayev |first7=D. |last8=Itkis |first8=M. G. |last9=Kovrizhnykh |first9=N. D. |last10=Kuznetsov |first10=D. A. |last11=Petrushkin |first11=O. V. |last12=Podshibiakin |first12=A. V. |last13=Polyakov |first13=A. N. |last14=Popeko |first14=A. G. |last15=Rogov |first15=I. S. |last16=Sagaidak |first16=R. N. |last17=Schlattauer |first17=L. |last18=Shubin |first18=V. D. |last19=Solovyev |first19=D. I. |last20=Tsyganov |first20=Yu. S. |last21=Voinov |first21=A. A. |last22=Subbotin |first22=V. G. |last23=Bublikova |first23=N. S. |last24=Voronyuk |first24=M. G. |last25=Sabelnikov |first25=A. V. |last26=Bodrov |first26=A. Yu. |last27=Aksenov |first27=N. V. |last28=Khalkin |first28=A. V. |last29=Gan |first29=Z. G. |last30=Zhang |first30=Z. Y. |last31=Huang |first31=M. H. |last32=Yang |first32=H. B. |display-authors=3 |title=Synthesis and decay properties of isotopes of element 110: Ds 273 and Ds 275 |journal=Physical Review C |date=6 May 2024 |volume=109 |issue=5 |doi=10.1103/PhysRevC.109.054307 |url=https://journals.aps.org/prc/pdf/10.1103/PhysRevC.109.054307?casa_token=Fq1mIpVgRQwAAAAA%3AEsc_kxg2-cFdX7x_lmOWSIXQtpjfWPWOti7jExQTd-xgmE8VVAy6irmU6Mq6TfHjMjGvom7ynggjx1I |access-date=11 May 2024 |language=en |issn=2469-9985}}</ref>
|dm=SF, α |year=2004|re=<sup>271</sup>Hs(—,α)
}}
{{isotopes summary/isotope
|mn=267m|sym=Sg|hl={{sort|100000|1.7 min}}|ref=<ref name=Ds2024/>
|dm=SF |year=2024|re=<sup>271</sup>Hs(—,α)
}}
{{isotopes summary/isotope
|mn=268|sym=Sg|hl={{sort|13000|13 s}}|ref=<ref name="276Ds-2023"/>
|dm=SF |year=2022|re=<sup>276</sup>Ds(—,2α)
}}
{{isotopes summary/isotope
|mn=269|sym=Sg|hl={{sort|840000|14 min}}|ref=<ref name="PuCa2017"/>
|dm=α |year=2010|re=<sup>285</sup>Fl(—,4α)
}}
{{isotopes summary/isotope
|mn=271|sym=Sg|hl={{sort|31000|31 s}}|ref=<ref name=PuCa2022/>
|dm=α, SF |year=2003|re=<sup>287</sup>Fl(—,4α)
}}
}}

[[Superheavy element]]s such as seaborgium are produced by bombarding lighter elements in [[particle accelerator]]s that induces [[fusion reaction]]s. Whereas most of the isotopes of seaborgium can be synthesized directly this way, some heavier ones have only been observed as decay products of elements with higher [[atomic number]]s.<ref name="fusion">{{cite journal |last1=Barber |first1=Robert C. |last2=Gäggeler |first2=Heinz W. |last3=Karol |first3=Paul J. |last4=Nakahara |first4=Hiromichi |last5=Vardaci |first5=Emanuele |last6=Vogt |first6=Erich |title=Discovery of the element with atomic number 112 (IUPAC Technical Report) |journal=Pure and Applied Chemistry |volume=81 |issue=7 |page=1331 |year=2009 |doi=10.1351/PAC-REP-08-03-05|doi-access=free }}</ref>

Depending on the energies involved, fusion reactions that generate superheavy elements are separated into "hot" and "cold". In hot fusion reactions, very light, high-energy projectiles are accelerated toward very heavy targets ([[actinide]]s), giving rise to compound nuclei at high excitation energy (~40–50&nbsp;[[electronvolt|MeV]]) that may either fission or evaporate several (3 to 5) neutrons.<ref name="fusion" /> In cold fusion reactions, the produced fused nuclei have a relatively low excitation energy (~10–20&nbsp;MeV), which decreases the probability that these products will undergo fission reactions. As the fused nuclei cool to the [[ground state]], they require emission of only one or two neutrons, and thus, allows for the generation of more neutron-rich products.<ref name="AM89">{{Cite journal |first1=Peter |last1=Armbruster |name-list-style=amp |first2=Gottfried |last2=Munzenberg |title=Creating superheavy elements |journal=Scientific American |volume=34 |pages=36–42 |year=1989}}</ref> The latter is a distinct concept from that of where nuclear fusion claimed to be achieved at room temperature conditions (see [[cold fusion]]).<ref>{{cite journal |doi=10.1016/0022-0728(89)80006-3 |title=Electrochemically induced nuclear fusion of deuterium |year=1989 |last1=Fleischmann |first1=Martin |last2=Pons |first2=Stanley |journal=Journal of Electroanalytical Chemistry and Interfacial Electrochemistry |volume=261 |issue=2 |pages=301–308}}</ref>

Seaborgium has no stable or naturally occurring isotopes. Several radioactive isotopes have been synthesized in the laboratory, either by fusing two atoms or by observing the decay of heavier elements. Thirteen different isotopes of seaborgium have been reported with mass numbers 258–269 and 271, four of which, seaborgium-261, -263, -265, and -267, have known [[metastable state]]s. All of these decay only through alpha decay and spontaneous fission, with the single exception of seaborgium-261 that can also undergo [[electron capture]] to dubnium-261.<ref name="nuclidetable" />

There is a trend toward increasing half-lives for the heavier isotopes, though [[even and odd atomic nuclei#Even proton, odd neutron|even–odd]] isotopes are generally more stable than their neighboring [[even and odd atomic nuclei#Even proton, even neutron|even–even]] isotopes, because the odd neutron leads to increased hindrance of spontaneous fission;<ref name=SFparity>{{cite journal |doi=10.1140/epja/s10050-022-00896-3 |last=Khuyagbaatar |first=J. |date=2022 |title=Fission-stability of high-K states in superheavy nuclei |journal=The European Physical Journal A |volume=58 |issue=243|page=243 |bibcode=2022EPJA...58..243K |s2cid=254658975 |doi-access=free }}</ref> among known seaborgium isotopes, alpha decay is the predominant decay mode in even–odd nuclei whereas fission dominates in [[Even-even nucleus|even–even nuclei]]. Three of the heaviest known isotopes, <sup>267</sup>Sg, <sup>269</sup>Sg, and <sup>271</sup>Sg, are also the longest-lived, having half-lives on the order of 1 minute.<ref name="nuclidetable" /> Some other isotopes in this region are predicted to have comparable or even longer half-lives. Additionally, <sup>263</sup>Sg, <sup>265</sup>Sg, <sup>265m</sup>Sg, and <sup>268</sup>Sg<ref name="276Ds-2023"/> have half-lives measured in seconds. All the remaining isotopes have half-lives measured in milliseconds, with the exception of the shortest-lived isotope, <sup>261m</sup>Sg, with a half-life of only 92&nbsp;microseconds.<ref name="nuclidetable">{{cite web |url=http://www.nndc.bnl.gov/chart/reCenter.jsp?z=107&n=163 |title=Interactive Chart of Nuclides |publisher=Brookhaven National Laboratory |author=Sonzogni, Alejandro |location=National Nuclear Data Center |access-date=2008-06-06 |archive-date=2018-06-12 |archive-url=https://web.archive.org/web/20180612141714/http://www.nndc.bnl.gov/chart/reCenter.jsp?z=107&n=163 |url-status=dead }}</ref>

The proton-rich isotopes from <sup>258</sup>Sg to <sup>261</sup>Sg were directly produced by cold fusion; all heavier isotopes were produced from the repeated alpha decay of the heavier elements [[hassium]], [[darmstadtium]], and [[flerovium]], with the exceptions of the isotopes <sup>263m</sup>Sg, <sup>264</sup>Sg, <sup>265</sup>Sg, and <sup>265m</sup>Sg, which were directly produced by hot fusion through irradiation of actinide targets. The twelve isotopes of seaborgium have half-lives ranging from 92&nbsp;microseconds for <sup>261m</sup>Sg to 14&nbsp;minutes for <sup>269</sup>Sg.<ref name="PuCa2017" /><ref name="nuclidetable" />

==Predicted properties==
Very few properties of seaborgium or its compounds have been measured; this is due to its extremely limited and expensive production<ref name="Bloomberg">{{Cite web|url=https://www.bloomberg.com/news/features/2019-08-28/making-new-elements-doesn-t-pay-just-ask-this-berkeley-scientist|title=Making New Elements Doesn't Pay. Just Ask This Berkeley Scientist|last=Subramanian|first=S.|website=[[Bloomberg Businessweek]]|access-date=2020-01-18}}</ref> and the fact that seaborgium (and its parents) decays very quickly. A few singular chemistry-related properties have been measured, but properties of seaborgium metal remain unknown and only predictions are available.

===Physical===
Seaborgium is expected to be a solid under normal conditions and assume a [[body-centered cubic]] crystal structure, similar to its lighter [[congener (chemistry)|congener]] tungsten.<ref name="bcc" /> Early predictions estimated that it should be a very heavy metal with density around 35.0&nbsp;g/cm<sup>3</sup>,<ref name="Haire" /> but calculations in 2011 and 2013 predicted a somewhat lower value of 23–24&nbsp;g/cm<sup>3</sup>.<ref name="density" /><ref name="kratz" />

===Chemical===
Seaborgium is the fourth member of the 6d series of transition metals and the heaviest member of [[group 6 element|group 6]] in the periodic table, below [[chromium]], [[molybdenum]], and [[tungsten]]. All the members of the group form a diversity of oxoanions. They readily portray their group oxidation state of +6, although this is highly oxidising in the case of chromium, and this state becomes more and more stable to reduction as the group is descended: indeed, tungsten is the last of the 5d transition metals where all four 5d electrons participate in [[metallic bonding]].<ref name="Greenwood">{{Greenwood&Earnshaw2nd|pages=1002–39}}</ref> As such, seaborgium should have +6 as its most stable oxidation state, both in the gas phase and in aqueous solution, and this is the only positive oxidation state that is experimentally known for it; the +5 and +4 states should be less stable, and the +3 state, the most common for chromium, would be the least stable for seaborgium.<ref name="Haire" />

This stabilisation of the highest oxidation state occurs in the early 6d elements because of the similarity between the energies of the 6d and 7s orbitals, since the 7s orbitals are relativistically stabilised and the 6d orbitals are relativistically destabilised. This effect is so large in the seventh period that seaborgium is expected to lose its 6d electrons before its 7s electrons (Sg, [Rn]5f<sup>14</sup>6d<sup>4</sup>7s<sup>2</sup>; Sg<sup>+</sup>, [Rn]5f<sup>14</sup>6d<sup>3</sup>7s<sup>2</sup>; Sg<sup>2+</sup>, [Rn]5f<sup>14</sup>6d<sup>3</sup>7s<sup>1</sup>; Sg<sup>4+</sup>, [Rn]5f<sup>14</sup>6d<sup>2</sup>; Sg<sup>6+</sup>, [Rn]5f<sup>14</sup>). Because of the great destabilisation of the 7s orbital, Sg<sup>IV</sup> should be even more unstable than W<sup>IV</sup> and should be very readily oxidised to Sg<sup>VI</sup>. The predicted ionic radius of the hexacoordinate Sg<sup>6+</sup> ion is 65&nbsp;pm, while the predicted atomic radius of seaborgium is 128&nbsp;pm. Nevertheless, the stability of the highest oxidation state is still expected to decrease as Lr<sup>III</sup> &gt; Rf<sup>IV</sup> &gt; Db<sup>V</sup> &gt; Sg<sup>VI</sup>. Some predicted [[standard reduction potential]]s for seaborgium ions in aqueous acidic solution are as follows:<ref name="Haire" />

:{|
|-
| 2 SgO<sub>3</sub> + 2 H<sup>+</sup> + 2 e<sup>−</sup> || {{eqm}} Sg<sub>2</sub>O<sub>5</sub> + H<sub>2</sub>O || E<sup>0</sup> = −0.046 V
|-
| Sg<sub>2</sub>O<sub>5</sub> + 2 H<sup>+</sup> + 2 e<sup>−</sup> || {{eqm}} 2 SgO<sub>2</sub> + H<sub>2</sub>O || E<sup>0</sup> = +0.11 V
|-
| SgO<sub>2</sub> + 4 H<sup>+</sup> + e<sup>−</sup> || {{eqm}} Sg<sup>3+</sup> + 2 H<sub>2</sub>O || E<sup>0</sup> = −1.34 V
|-
| Sg<sup>3+</sup> + e<sup>−</sup> || {{eqm}} Sg<sup>2+</sup> || E<sup>0</sup> = −0.11 V
|-
| Sg<sup>3+</sup> + 3 e<sup>−</sup> || {{eqm}} Sg || E<sup>0</sup> = +0.27 V
|}

Seaborgium should form a very volatile [[hexafluoride]] (SgF<sub>6</sub>) as well as a moderately volatile hexachloride (SgCl<sub>6</sub>), pentachloride (SgCl<sub>5</sub>), and oxychlorides SgO<sub>2</sub>Cl<sub>2</sub> and SgOCl<sub>4</sub>.{{Fricke1975}} SgO<sub>2</sub>Cl<sub>2</sub> is expected to be the most stable of the seaborgium oxychlorides and to be the least volatile of the group 6 oxychlorides, with the sequence MoO<sub>2</sub>Cl<sub>2</sub> &gt; WO<sub>2</sub>Cl<sub>2</sub> &gt; SgO<sub>2</sub>Cl<sub>2</sub>.<ref name="Haire" /> The volatile seaborgium(VI) compounds SgCl<sub>6</sub> and SgOCl<sub>4</sub> are expected to be unstable to decomposition to seaborgium(V) compounds at high temperatures, analogous to MoCl<sub>6</sub> and MoOCl<sub>4</sub>; this should not happen for SgO<sub>2</sub>Cl<sub>2</sub> due to the much higher energy gap between the [[HOMO/LUMO|highest occupied]] and lowest unoccupied [[molecular orbital]]s, despite the similar Sg–Cl bond strengths (similarly to molybdenum and tungsten).<ref name="Kratz">{{cite journal |doi = 10.1351/pac200375010103 |url =https://www.degruyter.com/downloadpdf/j/pac.2003.75.issue-1/pac200375010103/pac200375010103.pdf |title = Critical evaluation of the chemical properties of the transactinide elements (IUPAC Technical Report) |date = 2003 |last1 = Kratz |first1 = J. V. |journal = Pure and Applied Chemistry |volume = 75 |issue = 1 |page = 103|s2cid =5172663 }}</ref>

Molybdenum and tungsten are very similar to each other and show important differences to the smaller chromium, and seaborgium is expected to follow the chemistry of tungsten and molybdenum quite closely, forming an even greater variety of oxoanions, the simplest among them being seaborgate, {{chem|Sg|O|4|2-}}, which would form from the rapid hydrolysis of {{chem|Sg(H|2|O)|6|6+}}, although this would take place less readily than with molybdenum and tungsten as expected from seaborgium's greater size. Seaborgium should hydrolyse less readily than tungsten in [[hydrofluoric acid]] at low concentrations, but more readily at high concentrations, also forming complexes such as SgO<sub>3</sub>F<sup>−</sup> and {{chem|SgOF|5|-}}: complex formation competes with hydrolysis in hydrofluoric acid.<ref name="Haire" />

==Experimental chemistry==
Experimental chemical investigation of seaborgium has been hampered due to the need to produce it one atom at a time, its short half-life, and the resulting necessary harshness of the experimental conditions.<ref name="carbonyl">{{Cite journal | doi = 10.1126/science.1255720| pmid = 25237098| title = Synthesis and detection of a seaborgium carbonyl complex| journal = Science| volume = 345| issue = 6203| pages = 1491–3| year = 2014| last1 = Even | first1 = J.| last2 = Yakushev | first2 = A.| last3 = Dullmann | first3 = C. E.| last4 = Haba | first4 = H.| last5 = Asai | first5 = M.| last6 = Sato | first6 = T. K.| last7 = Brand | first7 = H.| last8 = Di Nitto | first8 = A.| last9 = Eichler | first9 = R.| last10 = Fan | first10 = F. L.| last11 = Hartmann | first11 = W.| last12 = Huang | first12 = M.| last13 = Jager | first13 = E.| last14 = Kaji | first14 = D.| last15 = Kanaya | first15 = J.| last16 = Kaneya | first16 = Y.| last17 = Khuyagbaatar | first17 = J.| last18 = Kindler | first18 = B.| last19 = Kratz | first19 = J. V.| last20 = Krier | first20 = J.| last21 = Kudou | first21 = Y.| last22 = Kurz | first22 = N.| last23 = Lommel | first23 = B.| last24 = Miyashita | first24 = S.| last25 = Morimoto | first25 = K.| last26 = Morita | first26 = K.| last27 = Murakami | first27 = M.| last28 = Nagame | first28 = Y.| last29 = Nitsche | first29 = H.| last30 = Ooe | first30 = K.| display-authors = 29| bibcode = 2014Sci...345.1491E| s2cid = 206558746}} {{subscription required}}</ref> The isotope <sup>265</sup>Sg and its isomer <sup>265m</sup>Sg are advantageous for radiochemistry: they are produced in the <sup>248</sup>Cm(<sup>22</sup>Ne,5n) reaction.<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>

In the first experimental chemical studies of seaborgium in 1995 and 1996, seaborgium atoms were produced in the reaction <sup>248</sup>Cm(<sup>22</sup>Ne,4n)<sup>266</sup>Sg, thermalised, and reacted with an O<sub>2</sub>/HCl mixture. The adsorption properties of the resulting oxychloride were measured and compared with those of molybdenum and tungsten compounds. The results indicated that seaborgium formed a volatile oxychloride akin to those of the other group 6 elements, and confirmed the decreasing trend of oxychloride volatility down group 6:

:Sg + {{chem|O|2}} + 2 HCl → {{chem|SgO|2|Cl|2}} + {{chem|H|2}}

In 2001, a team continued the study of the gas phase chemistry of seaborgium by reacting the element with O<sub>2</sub> in a H<sub>2</sub>O environment. In a manner similar to the formation of the oxychloride, the results of the experiment indicated the formation of seaborgium oxide hydroxide, a reaction well known among the lighter group 6 homologues as well as the pseudohomologue [[uranium]].<ref>{{cite journal
|url=http://www-w2k.gsi.de/kernchemie/images/pdf_Artikel/Radiochim_Acta_89_737_2001.pdf 
|title=Physico-chemical characterization of seaborgium as oxide hydroxide 
|journal=Radiochim. Acta 
|volume=89 
|pages=737–741 
|date=2001 
|doi=10.1524/ract.2001.89.11-12.737 
|display-authors=8 
|last1=Huebener 
|first1=S. 
|last2=Taut 
|first2=S. 
|last3=Vahle 
|first3=A. 
|last4=Dressler 
|first4=R. 
|last5=Eichler 
|first5=B. 
|last6=Gäggeler 
|first6=H. W. 
|last7=Jost 
|first7=D. T. 
|last8=Piguet 
|first8=D. 
|last9=Türler 
|first9=A. 
|last10=Brüchle 
|first10=W. 
|issue=11–12_2001 
|s2cid=98583998 
|url-status=bot: unknown 
|archive-url=https://web.archive.org/web/20141025201143/http://www-w2k.gsi.de/kernchemie/images/pdf_Artikel/Radiochim_Acta_89_737_2001.pdf 
|archive-date=2014-10-25 
}}</ref>

:2 Sg + 3 {{chem|O|2}} → 2 {{chem|SgO|3}}
:{{chem|SgO|3}} + {{chem|H|2|O}} → {{chem|SgO|2|(OH)|2}}

Predictions on the aqueous chemistry of seaborgium have largely been confirmed. In experiments conducted in 1997 and 1998, seaborgium was eluted from cation-exchange resin using a HNO<sub>3</sub>/HF solution, most likely as neutral SgO<sub>2</sub>F<sub>2</sub> or the anionic complex ion [SgO<sub>2</sub>F<sub>3</sub>]<sup>−</sup> rather than {{chem|SgO|4|2-}}. In contrast, in 0.1 M [[nitric acid]], seaborgium does not elute, unlike molybdenum and tungsten, indicating that the hydrolysis of [Sg(H<sub>2</sub>O)<sub>6</sub>]<sup>6+</sup> only proceeds as far as the cationic complex [Sg(OH)<sub>4</sub>(H<sub>2</sub>O)]<sup>2+</sup> or [SgO(OH)<sub>3</sub>(H<sub>2</sub>O)<sub>2</sub>]<sup>+</sup>, while that of molybdenum and tungsten proceed to neutral [MO<sub>2</sub>(OH)<sub>2</sub>].<ref name="Haire" />

The only other oxidation state known for seaborgium other than the group oxidation state of +6 is the zero oxidation state. Similarly to its three lighter congeners, forming [[chromium hexacarbonyl]], [[molybdenum hexacarbonyl]], and [[tungsten hexacarbonyl]], seaborgium has been shown in 2014 to also form [[seaborgium hexacarbonyl]], Sg(CO)<sub>6</sub>. Like its molybdenum and tungsten homologues, seaborgium hexacarbonyl is a volatile compound that reacts readily with [[silicon dioxide]].<ref name="carbonyl" />

== Absence in nature ==
{{See also|Island of stability#Possible natural occurrence}}
Searches for long-lived [[Primordial nuclide|primordial]] nuclides of seaborgium in nature have all yielded negative results. One 2022 study estimated the concentration of seaborgium atoms in natural tungsten (its chemical homolog) is less than {{val|5.1|e=-15}} atom(Sg)/atom(W).<ref name=nat-scint>{{cite journal |last1=Belli |first1=P. |last2=Bernabei |first2=R. |last3=Cappella |first3=F. |last4=Caracciolo |first4=V. |last5=Cerulli |first5=R. |last6=Danevich |first6=F. A. |last7=Incicchitti |first7=A. |last8=Kasperovych |first8=D. V.|last9=Kobychev |first9=V. V. |last10=Laubenstein |first10=M. |last11=Poda |first11=D. V. |last12=Polischuk |first12=O. G. |last13=Sokur |first13=N. V. |last14=Tretyak |first14=V. I. |display-authors=3 |title=Search for naturally occurring seaborgium with radiopure <sup>116</sup>CdWO<sub>4</sub> crystal scintillators |date=2022 |journal=Physica Scripta |volume=97 |number=85302 |page=085302 |doi=10.1088/1402-4896/ac7a6d|bibcode=2022PhyS...97h5302B |s2cid=249902412 }}</ref>

==Notes==
{{notelist}}

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

== 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 |ref=CITEREFHoffman2000}}
* {{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|Seaborgium}}
* [http://www.rsc.org/periodic-table/podcast Chemistry in its element podcast] (MP3) from the [[Royal Society of Chemistry]]'s [[Chemistry World]]: [http://www.rsc.org/periodic-table/element/106/seaborgium#podcast Seaborgium]
* [http://www.periodicvideos.com/videos/106.htm Seaborgium] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)
* [http://www.webelements.com/webelements/elements/text/Sg/index.html WebElements.com – Seaborgium]
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[[Category:Seaborgium| ]]
[[Category:Chemical elements]]
[[Category:Transition metals]]
[[Category:Synthetic elements]]
[[Category:Glenn T. Seaborg]]
[[Category:Chemical elements with body-centered cubic structure]]