Editing Periodic table (section)

=== Synthetic elements ===
[[File:Glenn Seaborg - 1964.jpg|thumb|right|Glenn T. Seaborg]]
By 1936, the pool of missing elements from hydrogen to uranium had shrunk to four: elements 43, 61, 85, and 87 remained missing. Element 43 eventually became the first element to be synthesized artificially via nuclear reactions rather than discovered in nature. It was discovered in 1937 by Italian chemists [[Emilio Segrè]] and [[Carlo Perrier]], who named their discovery [[technetium]], after the Greek word for "artificial".<ref>Scerri, pp. 313–321</ref> Elements 61 ([[promethium]]) and 85 ([[astatine]]) were likewise produced artificially in 1945 and 1940 respectively; element 87 ([[francium]]) became the last element to be discovered in nature, by French chemist [[Marguerite Perey]] in 1939.<ref>Scerri, pp. 322–340</ref>{{efn|Technetium, promethium, astatine, neptunium, and plutonium were eventually discovered to occur in nature as well, albeit in tiny traces. See [[timeline of chemical element discoveries]].}} The elements beyond uranium were likewise discovered artificially, starting with [[Edwin McMillan]] and [[Philip Abelson]]'s 1940 discovery of [[neptunium]] (via bombardment of uranium with neutrons).<ref name="Scerri354">Scerri, p. 354–6</ref> [[Glenn T. Seaborg]] and his team at the [[Lawrence Berkeley National Laboratory]] (LBNL) continued discovering transuranium elements, starting with [[plutonium]] in 1941, and discovered that contrary to previous thinking, the elements from actinium onwards were congeners of the lanthanides rather than transition metals.<ref name=Seaborg /> Bassett (1892), Werner (1905), and the French engineer [[Charles Janet]] (1928) had previously suggested this, but their ideas did not then receive general acceptance.<ref name=Thyssen /> Seaborg thus called them the actinides.<ref name="Seaborg">{{cite web |url=https://fas.org/sgp/othergov/doe/lanl/orgs/nmt/97summer.pdf |title=Source of the Actinide Concept |last=Seaborg |first=Glenn T. |date=1997 |website=fas.org |publisher=Los Alamos National Laboratory |access-date=28 March 2021 |archive-date=15 August 2021 |archive-url=https://web.archive.org/web/20210815074120/https://fas.org/sgp/othergov/doe/lanl/orgs/nmt/97summer.pdf |url-status=live }}</ref> Elements up to 101 (named mendelevium in honour of Mendeleev) were synthesized up to 1955, either through neutron or alpha-particle irradiation, or in nuclear explosions in the cases of 99 (einsteinium) and 100 (fermium).<ref name=Scerri354/>

A significant controversy arose with elements 102 through 106 in the 1960s and 1970s, as competition arose between the LBNL team (now led by [[Albert Ghiorso]]) and a team of Soviet scientists at the [[Joint Institute for Nuclear Research]] (JINR) led by [[Georgy Flyorov]]. Each team claimed discovery, and in some cases each proposed their own name for the element, creating an [[element naming controversy]] that lasted decades. These elements were made by bombardment of actinides with light ions.<ref>Scerri, pp. 356–9</ref> IUPAC at first adopted a hands-off approach, preferring to wait and see if a consensus would be forthcoming. But as it was also the height of the [[Cold War]], it became clear that this would not happen. As such, IUPAC and the [[International Union of Pure and Applied Physics]] (IUPAP) created a [[Transfermium Working Group]] (TWG, fermium being element 100) in 1985 to set out criteria for discovery,<ref>{{cite journal |last1=Öhrström |first1=Lars |last2=Holden |first2=Norman E. |date=2016 |title=The Three-letter Element Symbols |journal=Chemistry International |volume=38 |issue=2 |pages=4–8 |doi=10.1515/ci-2016-0204 |s2cid=124737708 |doi-access=free }}</ref> which were published in 1991.<ref>{{cite journal |last1=Wapstra |first1=A. H. |date=1991 |title=Criteria that must be satisfied for the discovery of a new chemical element to be recognized |url=https://old.iupac.org/reports/1991/6306wapstra/index.html |journal=Pure and Applied Chemistry |volume=63 |issue=6 |pages=879–886 |doi=10.1351/pac199163060879 |s2cid=95737691 |access-date=18 October 2022|url-access=subscription }}</ref> After some further controversy, these elements received their final names in 1997, including seaborgium (106) in honour of Seaborg.<ref>{{cite journal | doi=10.1351/pac199769122471|title=Names and symbols of transfermium elements (IUPAC Recommendations 1997) | year=1997 | journal=Pure and Applied Chemistry | volume=69 | pages=2471–2474 | issue=12| doi-access=free }}</ref>

[[File:Yuri Oganessian.jpg|thumb|right|Yuri Oganessian]]
The TWG's criteria were used to arbitrate later element discovery claims from LBNL and JINR, as well as from research institutes in Germany ([[GSI Helmholtz Centre for Heavy Ion Research|GSI]]) and Japan ([[Riken]]).<ref>{{cite journal |last1=Hofmann |first1=Sigurd |date=2019 |title=Criteria for New Element Discovery |journal=Chemistry International |volume=41 |issue=1 |pages=10–15 |doi=10.1515/ci-2019-0103|doi-access=free }}</ref> Currently, consideration of discovery claims is performed by a [[IUPAC/IUPAP Joint Working Party]]. After priority was assigned, the elements were officially added to the periodic table, and the discoverers were invited to propose their names.<ref name="IUPAC-redbook" /> By 2016, this had occurred for all elements up to 118, therefore completing the periodic table's first seven rows.<ref name="IUPAC-redbook">{{cite web |url=https://iupac.org/what-we-do/periodic-table-of-elements/ |title=Periodic Table of Elements |author=<!--Not stated--> |date=2021 |website=iupac.org |publisher=IUPAC |access-date=3 April 2021 |archive-date=10 April 2016 |archive-url=https://web.archive.org/web/20160410043726/https://iupac.org/what-we-do/periodic-table-of-elements/ |url-status=live }}</ref><ref name="finally">{{cite journal|last=Scerri|first=E.|author-link=Eric Scerri|year=2012|journal=Chemistry International|volume=34|issue=4|url=https://www.iupac.org/publications/ci/2012/3404/ud.html|title=Mendeleev's Periodic Table Is Finally Completed and What To Do about Group 3?|url-status=live|archive-url=https://web.archive.org/web/20170705051357/https://www.iupac.org/publications/ci/2012/3404/ud.html|archive-date=5 July 2017|doi=10.1515/ci.2012.34.4.28|doi-access=free}}</ref> The discoveries of elements beyond 106 were made possible by techniques devised by [[Yuri Oganessian]] at the JINR: cold fusion (bombardment of lead and bismuth by heavy ions) made possible the 1981–2004 discoveries of elements 107 through 112 at GSI and 113 at Riken, and he led the JINR team (in collaboration with American scientists) to discover elements 114 through 118 using hot fusion (bombardment of actinides by calcium ions) in 1998–2010.<ref>Scerri, pp. 356–363</ref><ref name="Chapman">{{cite journal|last1=Chapman|first1=Kit|title=What it takes to make a new element|journal=[[Chemistry World]]|date=30 November 2016|url=https://www.chemistryworld.com/what-it-takes-to-make-a-new-element/1017677.article|publisher=[[Royal Society of Chemistry]]|access-date=22 March 2022|archive-date=28 October 2017|archive-url=https://web.archive.org/web/20171028122035/https://www.chemistryworld.com/what-it-takes-to-make-a-new-element/1017677.article|url-status=live }}</ref> The heaviest known element, oganesson (118), is named in Oganessian's honour. Element 114 is named flerovium in honour of his predecessor and mentor Flyorov.<ref name=Chapman/>

In celebration of the periodic table's 150th anniversary, the [[United Nations]] declared the year 2019 as the International Year of the Periodic Table, celebrating "one of the most significant achievements in science".<ref name=":1">{{Cite news|url=https://www.bbc.com/news/science-environment-47008289|title=150 years of the periodic table: Test your knowledge |last=Briggs|first=Helen|date=29 January 2019|access-date=8 February 2019|language=en-GB|archive-url=https://web.archive.org/web/20190209210210/https://www.bbc.com/news/science-environment-47008289|archive-date=9 February 2019|url-status=live}}</ref> The discovery criteria set down by the TWG were updated in 2020 in response to experimental and theoretical progress that had not been foreseen in 1991.<ref>{{cite journal |last1=Hofmann |first1=Sigurd |last2=Dmitriev |first2=Sergey N. |last3=Fahlander |first3=Claes |last4=Gates |first4=Jacklyn M. |last5=Roberto |first5=James B. |last6=Sakai |first6=Hideyuki |date=4 August 2020 |title=On the discovery of new elements (IUPAC/IUPAP Report) |s2cid-access=free |journal=Pure and Applied Chemistry |volume=92 |issue=9 |pages=1387–1446 |doi=10.1515/pac-2020-2926 |s2cid=225377737 |doi-access=free }}</ref> Today, the periodic table is among the most recognisable icons of chemistry.<ref name="Lemonick" /> IUPAC is involved today with many processes relating to the periodic table: the recognition and naming of new elements, recommending group numbers and collective names, and the updating of atomic weights.<ref name="IUPAC-redbook" />