Editing Lawrencium (section)

==History==
[[File:96904536.thumb3.jpeg|thumb|left|[[Albert Ghiorso]] updating the periodic table in April 1961, writing the symbol "Lw" in as element 103. Codiscoverers Latimer, Sikkeland, and Larsh (left to right) look on.]]
In 1958, scientists at [[Lawrence Berkeley National Laboratory]] claimed the discovery of element 102, now called [[nobelium]]. At the same time, they also tried to synthesize element 103 by bombarding the same [[curium]] target used with [[nitrogen]]-14 ions. Eighteen tracks were noted, with [[decay energy]] around {{val|9|1|u=[[electronvolt|MeV]]}} and half-life around 0.25 s; the Berkeley team noted that while the cause could be the production of an isotope of element 103, other possibilities could not be ruled out. While the data agrees reasonably with that later discovered for <sup>257</sup>Lr ([[alpha decay]] energy 8.87&nbsp;MeV, half-life 0.6&nbsp;s), the evidence obtained in this experiment fell far short of the strength required to conclusively demonstrate synthesis of element 103. A follow-up on this experiment was not done, as the target was destroyed.<ref name = "emsley2011">{{cite book|last=Emsley|first=John|title=Nature's Building Blocks|date=2011}}</ref><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> Later, in 1960, the Lawrence Berkeley Laboratory attempted to synthesize the element by bombarding <sup>252</sup>[[californium|Cf]] with <sup>10</sup>B and <sup>11</sup>B. The results of this experiment were not conclusive.<ref name="emsley2011" />

The first important work on element 103 was done at Berkeley by the [[nuclear physics|nuclear-physics]] team of [[Albert Ghiorso]], Torbjørn Sikkeland, Almon Larsh, Robert M. Latimer, and their co-workers on February 14, 1961.<ref>{{cite web|title=This Month in Lab History…Lawrencium Added to Periodic Table |url=https://today.lbl.gov/2013/04/09/this-month-in-lab-historylawrencium-added-to-periodic-table/ |website=today.lbl.gov |publisher=Lawrence Berkeley National Laboratory |access-date=13 February 2021 |date=9 April 2013 |quote=Lawrencium (Lw) was first synthesized Feb. 14, 1961, by a team led by Ghiorso, who was co-discoverer of a record 12 chemical elements on the periodic table.}}</ref> The first atoms of lawrencium were reportedly made by bombarding a three-[[milligram]] target consisting of three isotopes of [[californium]] with [[boron]]-10 and boron-11 [[atomic nucleus|nuclei]] from the Heavy Ion Linear Accelerator (HILAC).<ref name="Lr">{{cite journal|first1=Albert|last1=Ghiorso|author-link=Albert Ghiorso|last2=Sikkeland|first2=T. |last3=Larsh|first3=A. E. |last4=Latimer|first4=R. M. |journal=Phys. Rev. Lett.|volume=6|page=473|date=1961|bibcode = 1961PhRvL...6..473G |doi = 10.1103/PhysRevLett.6.473|title=New Element, Lawrencium, Atomic Number 103|issue=9|url=https://escholarship.org/uc/item/2s43n491|doi-access=free}}</ref> The Berkeley team reported that the [[isotope]] <sup>257</sup>103 was detected in this manner, and that it decayed by emitting an 8.6&nbsp;MeV [[alpha particle]] with a [[half-life]] of {{val|8|2|u=s}}.<ref name="93TWG" /> This identification was later corrected to <sup>258</sup>103,<ref name="Lr" /> as later work proved that <sup>257</sup>Lr did not have the properties detected, but <sup>258</sup>Lr did.<ref name="93TWG" /> This was considered at the time to be convincing proof of synthesis of element 103: while the mass assignment was less certain and proved to be mistaken, it did not affect the arguments in favor of element 103 having been synthesized. Scientists at [[Joint Institute for Nuclear Research]] in [[Dubna]] (then in the [[Soviet Union]]) raised several criticisms: all but one were answered adequately. The exception was that <sup>252</sup>Cf was the most common isotope in the target, and in the reactions with <sup>10</sup>B, <sup>258</sup>Lr could only have been produced by emitting four neutrons, and emitting three neutrons was expected to be much less likely than emitting four or five. This would lead to a narrow yield curve, not the broad one reported by the Berkeley team. A possible explanation was that there was a low number of events attributed to element 103.<ref name="93TWG" /> This was an important intermediate step to the unquestioned discovery of element 103, although the evidence was not completely convincing.<ref name="93TWG" /> The Berkeley team proposed the name "lawrencium" with symbol "Lw", after [[Ernest Lawrence]], inventor of the [[cyclotron]]. The IUPAC Commission on Nomenclature of Inorganic Chemistry accepted the name, but changed the symbol to "Lr".<ref name="qqq">{{cite journal|first=Norman N.|last=Greenwood|journal=Pure Appl. Chem.|volume=69|issue=1|pages=179–184|title=Recent developments concerning the discovery of elements 101–111|date=1997|doi=10.1351/pac199769010179|s2cid=98322292|url=http://old.iupac.org/publications/pac/1997/pdf/6901x0179.pdf}}</ref> This acceptance of the discovery was later characterized as being hasty by the Dubna team.<ref name="93TWG" />

:{{nuclide|Cf|252}} + {{nuclide|B|11}} → {{nuclide|Lr|263}}* → {{nuclide|Lr|258}} + 5 {{nuclide|neutronium|1}}

The first work at Dubna on element 103 came in 1965, when they reported to have made <sup>256</sup>103 in 1965 by bombarding <sup>243</sup>[[americium|Am]] with <sup>18</sup>[[oxygen|O]], identifying it indirectly from its [[decay product|granddaughter]] [[fermium]]-252. The half-life they reported was somewhat too high, possibly due to background events. Later 1967 work on the same reaction identified two decay energies in the ranges 8.35–8.50&nbsp;MeV and 8.50–8.60&nbsp;MeV: these were assigned to <sup>256</sup>103 and <sup>257</sup>103.<ref name="93TWG" /> Despite repeat attempts, they were unable to confirm assignment of an alpha emitter with a half-life of 8 seconds to <sup>257</sup>103.<ref>{{cite journal|first=G. N.|last=Flerov|title=On the nuclear properties of the isotopes <sup>256</sup>103 and <sup>257</sup>103|journal=Nucl. Phys. A|volume=106|issue=2|page=476|date=1967|bibcode=1967NuPhA.106..476F|doi=10.1016/0375-9474(67)90892-5}}</ref><ref>{{cite journal | last=Donets | first=E. D. | last2=Shchegolev | first2=V. A. | last3=Ermakov | first3=V. A. | title=Synthesis of the isotope of element 103 (lawrencium) with mass number 256 | journal=Soviet Atomic Energy | volume=19 | issue=2 | year=1965 | issn=0038-531X | doi=10.1007/BF01126414 | pages=995–999}}
</ref> The Russians proposed the name "rutherfordium" for the new element in 1967:<ref name = "emsley2011" /><ref name=Karpenko/> this name was later proposed by Berkeley for [[rutherfordium|element 104]].<ref name=Karpenko>{{cite journal |last1=Karpenko |first1=V. |date=1980 |title=The Discovery of Supposed New Elements: Two Centuries of Errors |journal=Ambix |volume=27 |issue=2 |pages=77–102 |doi=10.1179/amb.1980.27.2.77}}</ref>

:{{nuclide|Am|243}} + {{nuclide|O|18}} → {{nuclide|Lr|261}}* → {{nuclide|Lr|256}} + 5 {{nuclide|neutronium|1}}

Further experiments in 1969 at Dubna and in 1970 at Berkeley demonstrated an [[actinide]] chemistry for the new element; so by 1970 it was known that element 103 is the last actinide.<ref name="93TWG" /><ref>{{cite book|date = 2005|title = Theoretical chemistry and physics of heavy and superheavy element|page = 57|publisher = Springer|isbn=1-4020-1371-X|author =Kaldor, Uzi|author2 =Wilson, Stephen|name-list-style =amp}}</ref> In 1970, the Dubna group reported the synthesis of <sup>255</sup>103 with half-life 20&nbsp;s and alpha decay energy 8.38&nbsp;MeV.<ref name="93TWG" /> However, it was not until 1971, when the nuclear physics team at University of California at Berkeley successfully did a whole series of experiments aimed at measuring the nuclear decay properties of the lawrencium isotopes with mass numbers 255 to 260,<ref name="Silva16412">{{harvnb|Silva|2011|pp=1641–2}}</ref><ref name="Eskola">{{cite journal|journal=Phys. Rev. C| volume=4|issue=2|pages=632–642|date=1971|title=Studies of Lawrencium Isotopes with Mass Numbers 255 Through 260|author=Eskola, Kari|author2=Eskola, Pirkko|author3=Nurmia, Matti|author4=Albert Ghiorso |doi=10.1103/PhysRevC.4.632|bibcode = 1971PhRvC...4..632E | url=http://www.escholarship.org/uc/item/1476j5n1}}</ref> that all previous results from Berkeley and Dubna were confirmed, apart from the Berkeley's group initial erroneous assignment of their first produced isotope to <sup>257</sup>103 instead of the probably correct <sup>258</sup>103.<ref name="93TWG" /> All final doubts were dispelled in 1976 and 1977 when the energies of [[X-ray]]s emitted from <sup>258</sup>103 were measured.<ref name="93TWG" />

[[File:Ernest Lawrence.jpg|thumb|upright=0.9|right|The element was named after [[Ernest Lawrence]].]]
In 1971, the IUPAC granted the discovery of lawrencium to the Lawrence Berkeley Laboratory, even though they did not have ideal data for the element's existence. But in 1992, the [[IUPAC]] Transfermium Working Group (TWG) officially recognized the nuclear physics teams at Dubna and Berkeley as co-discoverers of lawrencium, concluding that while the 1961 Berkeley experiments were an important step to lawrencium's discovery, they were not yet fully convincing; and while the 1965, 1968, and 1970 Dubna experiments came very close to the needed level of confidence taken together, only the 1971 Berkeley experiments, which clarified and confirmed previous observations, finally resulted in complete confidence in the discovery of element 103.<ref name = "emsley2011" /><ref name="qqq" /> Because the name "lawrencium" had been in use for a long time by this point, it was retained by IUPAC,<ref name = "emsley2011" /> and in August 1997, the [[International Union of Pure and Applied Chemistry]] (IUPAC) ratified the name lawrencium and the symbol "Lr" during a meeting in [[Geneva]].<ref name="qqq" />