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{{Infobox lawrencium}}
'''Lawrencium''' is a [[synthetic element|synthetic chemical element]]; it has [[Chemical symbol|symbol]] '''Lr''' (formerly '''Lw''') and [[atomic number]] 103. It is named after [[Ernest Lawrence]], inventor of the [[cyclotron]], a device that was used to discover many artificial [[radioactive]] elements. A radioactive [[metal]], lawrencium is the eleventh [[transuranium element]], the third transfermium,  and the last member of the [[actinide]] series. Like all elements with atomic number over 100, lawrencium can only be produced in [[particle accelerator]]s by bombarding lighter elements with charged particles. Fourteen [[isotopes of lawrencium]] are currently known; the most stable is <sup>266</sup>Lr with [[half-life]] 11 hours, but the shorter-lived <sup>260</sup>Lr (half-life 2.7 minutes) is most commonly used in chemistry because it can be produced on a larger scale.

Chemistry experiments confirm that lawrencium behaves as a heavier [[Homologous series|homolog]] to [[lutetium]] in the [[periodic table]], and is a [[valence (chemistry)|trivalent]] element. It thus could also be classified as the first of the 7th-period [[transition metal]]s. Its [[electron configuration]] is anomalous for its position in the periodic table, having an [[atomic orbital|s<sup>2</sup>p]] configuration instead of the s<sup>2</sup>d configuration of its homolog lutetium. However, this does not appear to affect lawrencium's chemistry.

In the 1950s, 1960s, and 1970s, many claims of the synthesis of element 103 of varying quality were made from laboratories in the [[Soviet Union]] and the [[United States]]. The priority of the discovery and therefore the [[transfermium wars|name of the element was disputed]] between Soviet and American scientists. The [[International Union of Pure and Applied Chemistry]] (IUPAC) initially established ''lawrencium'' as the official name for the element and gave the American team credit for the discovery; this was reevaluated in 1992, giving both teams shared credit for the discovery but not changing the element's name.

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

==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|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}} (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" />

==Characteristics==

===Physical===
Lawrencium is the last [[actinide]]. Authors considering the subject generally consider it a [[group 3 element]], along with [[scandium]], [[yttrium]], and [[lutetium]], as its filled f-shell is expected to make it resemble the other [[period 7 element|7th-period]] [[transition metal]]s. In the [[periodic table]], it is to the right of the actinide [[nobelium]], to the left of the 6d transition metal [[rutherfordium]], and under the lanthanide lutetium with which it shares many physical and chemical properties. Lawrencium is expected to be a solid under normal conditions and have a [[hexagonal close-packed]] crystal structure (<sup>''c''</sup>/<sub>''a''</sub>&nbsp;=&nbsp;1.58), similar to its lighter [[congener (chemistry)|congener]] lutetium, though this is not yet known experimentally.<ref name="hcp" /> The [[enthalpy]] of [[sublimation (phase transition)|sublimation]] of lawrencium is estimated at 352&nbsp;kJ/mol, close to the value of lutetium and strongly suggesting that metallic lawrencium is trivalent with three electrons [[delocalized electron|delocalized]], a prediction also supported by a systematic extrapolation of the values of [[heat of vaporization]], [[bulk modulus]], and [[atomic volume]] of neighboring elements to lawrencium.<ref name="Silva1644">{{harvnb|Silva|2011|p=1644}}</ref> This makes it unlike the immediately preceding late actinides which are known to be (fermium and mendelevium) or expected to be (nobelium) divalent.<ref>{{harvnb|Silva|2011|p=1639}}</ref> The estimated enthalpies of vaporization show that lawrencium deviates from the trend of the late actinides and instead matches the trend of the succeeding 6d elements rutherfordium and dubnium,<ref name=insights/><ref name=Jensen2015/> consistent with lawrencium's interpretation as a group 3 element.<ref name="Jensen2015">{{cite journal |last1=Jensen |first1=William B. |date=2015 |title=The positions of lanthanum (actinium) and lutetium (lawrencium) in the periodic table: an update |url=https://link.springer.com/article/10.1007/s10698-015-9216-1 |journal=Foundations of Chemistry |volume=17 |issue= |pages=23–31 |doi=10.1007/s10698-015-9216-1 |s2cid=98624395 |access-date=28 January 2021 |archive-date=30 January 2021 |archive-url=https://web.archive.org/web/20210130011116/https://link.springer.com/article/10.1007/s10698-015-9216-1 |url-status=live |url-access=subscription }}</ref> Some scientists prefer to end the actinides with nobelium and consider lawrencium to be the first transition metal of the seventh period.<ref>{{cite web |url=https://www.webelements.com/ |title=WebElements |last=Winter |first=Mark |date=1993–2022 |website= |publisher=The University of Sheffield and WebElements Ltd, UK |access-date=5 December 2022 |quote=}}</ref><ref>{{cite book |last=Cowan |first=Robert D. |date=1981 |title=The Theory of Atomic Structure and Spectra |url= |location= |publisher=University of California Press |page=598 |isbn=978-0-520-90615-0}}</ref>

Lawrencium is expected to be a trivalent, silvery metal, easily [[redox|oxidized]] by air, [[steam]], and [[acid]]s,<ref name="Emsley2011">{{cite book|author=John Emsley|title=Nature's Building Blocks: An A-Z Guide to the Elements|url=https://books.google.com/books?id=4BAg769RfKoC&pg=PA368|date= 2011|publisher=Oxford University Press|isbn=978-0-19-960563-7|pages=278–9}}</ref> and having an atomic volume similar to that of lutetium and a trivalent [[metallic radius]] of 171&nbsp;[[picometer|pm]].<ref name="Silva1644" /> It is expected to be a rather heavy metal with a density of around 14.4&nbsp;g/cm<sup>3</sup>.<ref name="density" /> It is also predicted to have a [[melting point]] of around 1900&nbsp;[[kelvin|K]] (1600&nbsp;[[Celsius|°C]]<!--DON'T CHANGE IT, FALSE PRECISION OTHERWISE-->), not far from the value for lutetium (1925&nbsp;K).<ref>{{cite book | editor = Lide, D. R. | title = CRC Handbook of Chemistry and Physics | edition = 84th | location = Boca Raton, FL | publisher = CRC Press | date = 2003 }}</ref>

===Chemical===
[[File:F-block elution sequence.png|thumb|right|upright=1.4|Elution sequence of the late trivalent lanthanides and actinides, with ammonium α-HIB as eluant: the broken curve for lawrencium is a prediction.]]
In 1949, [[Glenn T. Seaborg]], who devised the [[actinide concept]], predicted that element 103 (lawrencium) should be the last actinide and that the {{chem2|Lr(3+)}} ion should be about as stable as {{chem2|Lu(3+)}} in [[aqueous solution]]. It was not until decades later that element 103 was finally conclusively synthesized and this prediction was experimentally confirmed.<ref name="Silva16447">{{harvnb|Silva|2011|pp=1644–7}}</ref>

Studies on the element, performed in 1969, showed that lawrencium reacts with [[chlorine]] to form a product that was most likely the trichloride, {{chem2|LrCl3}}. Its [[volatility (chemistry)|volatility]] was found to be similar to the chlorides of [[curium]], [[fermium]], and [[nobelium]] and much less than that of [[rutherfordium]] chloride. In 1970, chemical studies were performed on 1500&nbsp;atoms of <sup>256</sup>Lr, comparing it with divalent ([[nobelium|No]], [[barium|Ba]], [[radium|Ra]]), trivalent ([[fermium|Fm]], [[californium|Cf]], [[curium|Cm]], [[americium|Am]], [[actinium|Ac]]), and tetravalent ([[thorium|Th]], [[plutonium|Pu]]) elements. It was found that lawrencium [[extraction (chemistry)|coextracted]] with the trivalent ions, but the short half-life of <sup>256</sup>Lr precluded a confirmation that it [[elution|eluted]] ahead of {{chem2|[[mendelevium|Md]](3+)}} in the elution sequence.<ref name="Silva16447" /> Lawrencium occurs as the trivalent {{chem2|Lr(3+)}} ion in aqueous solution and hence its compounds should be similar to those of the other trivalent actinides: for example, lawrencium(III) [[fluoride]] ({{chem2|LrF3}}) and [[hydroxide]] ({{chem2|Lr(OH)3}}) should both be insoluble in water.<ref name="Silva16447" /> Due to the [[lanthanide contraction|actinide contraction]], the [[ionic radius]] of {{chem2|Lr(3+)}} should be smaller than that of {{chem2|Md(3+)}}, and it should elute ahead of {{chem2|Md(3+)}} when [[ammonium α-hydroxyisobutyrate]] (ammonium α-HIB) is used as an eluant.<ref name="Silva16447" /> Later 1987 experiments on the longer-lived isotope <sup>260</sup>Lr confirmed lawrencium's trivalency and that it eluted in roughly the same place as [[erbium]], and found that lawrencium's ionic radius was {{val|88.6|0.3|u=[[picometer|pm]]}}, larger than would be expected from simple extrapolation from [[periodic trend]]s.<ref name="Silva16447" /> Later 1988 experiments with more lawrencium atoms refined this to {{val|88.1|0.1|u=pm}} and calculated an [[enthalpy of hydration]] value of {{val|−3685|13|u=kJ/mol}}.<ref name="Silva16447" /> It was also found that the actinide contraction at the end of the actinides was larger than the analogous lanthanide contraction, with the exception of the last actinide, lawrencium: the cause was speculated to be relativistic effects.<ref name="Silva16447" />

It has been speculated that the 7s electrons are relativistically stabilized, so that in reducing conditions, only the 7p<sub>1/2</sub> electron would be ionized, leading to the monovalent {{chem2|Lr(+)}} ion. However, all experiments to reduce {{chem2|Lr(3+)}} to {{chem2|Lr(2+)}} or {{chem2|Lr(+)}} in aqueous solution were unsuccessful, similarly to lutetium. On the basis of this, the [[standard electrode potential]] of the ''E''°({{chem2|Lr(3+) → Lr(+)}}) couple was calculated to be less than −1.56&nbsp;[[volt|V]], indicating that the existence of {{chem2|Lr(+)}} ions in aqueous solution was unlikely. The upper limit for the ''E''°({{chem2|Lr(3+) → Lr(2+)}}) couple was predicted to be −0.44&nbsp;V: the values for ''E''°({{chem2|Lr(3+) → Lr}}) and ''E''°({{chem2|Lr(4+) → Lr(3+)}}) are predicted to be −2.06&nbsp;V and +7.9&nbsp;V.<ref name="Silva16447" /> The stability of the group oxidation state in the 6d transition series decreases as [[rutherfordium|Rf]]<sup>IV</sup> &gt; [[dubnium|Db]]<sup>V</sup> &gt; [[seaborgium|Sg]]<sup>VI</sup>, and lawrencium continues the trend with Lr<sup>III</sup> being more stable than Rf<sup>IV</sup>.<ref>{{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| page=1686}}</ref>

In the molecule lawrencium dihydride ({{chem2|LrH2}}), which is predicted to be [[bent molecular geometry|bent]], the 6d orbital of lawrencium is not expected to play a role in the bonding, unlike that of [[lanthanum dihydride]] ({{chem2|LaH2}}). {{chem2|LaH2}} has La–H bond distances of 2.158&nbsp;Å, while {{chem2|LrH2}} should have shorter Lr–H bond distances of 2.042&nbsp;Å due to the relativistic contraction and stabilization of the 7s and 7p orbitals involved in the bonding, in contrast to the core-like 5f subshell and the mostly uninvolved 6d subshell. In general, molecular {{chem2|LrH2}} and LrH are expected to resemble the corresponding [[thallium]] species (thallium having a 6s<sup>2</sup>6p<sup>1</sup> valence configuration in the gas phase, like lawrencium's 7s<sup>2</sup>7p<sup>1</sup>) more than the corresponding [[lanthanide]] species.<ref>{{cite journal|last1=Balasubramanian|first1=K.|date=4 December 2001|title=Potential energy surfaces of Lawrencium and Nobelium dihydrides (LrH<sub>2</sub> and NoH<sub>2</sub>)|journal=Journal of Chemical Physics|volume=116|issue=9|pages=3568–75|bibcode=2002JChPh.116.3568B|doi=10.1063/1.1446029}}</ref> The electron configurations of {{chem2|Lr(+)}} and {{chem2|Lr(2+)}} are expected to be 7s<sup>2</sup> and 7s<sup>1</sup> respectively. However, in species where all three valence electrons of lawrencium are ionized to give at least formally the {{chem2|Lr(3+)}} cation, lawrencium is expected to behave like a typical actinide and the heavier congener of lutetium, especially because the first three ionization potentials of lawrencium are predicted to be similar to those of lutetium. Hence, unlike thallium but like lutetium, lawrencium would prefer to form {{chem2|LrH3}} than LrH, and Lr[[metal carbonyl|CO]] is expected to be similar to the also unknown LuCO, both metals having valence configuration σ<sup>2</sup>π<sup>1</sup> in their monocarbonyls. The pπ–dπ bond is expected to be seen in {{chem2|LrCl3}} just as it is for {{chem2|LuCl3}} and more generally all the {{chem2|LnCl3}}. The complex anion {{chem2|[Lr(C5H4SiMe3)3](−)}} is expected to be stable with a configuration of 6d<sup>1</sup> for lawrencium; this 6d orbital would be [[HOMO/LUMO|its highest occupied molecular orbital]]. This is analogous to the electronic structure of the analogous lutetium compound.<ref name=peculiar>
{{cite journal |last1=Xu |first1=Wen-Hua |last2=Pyykkö |first2=Pekka |date=8 June 2016 |url=http://pubs.rsc.org/-/content/articlehtml/2016/cp/c6cp02706g |title=Is the chemistry of lawrencium peculiar |journal=Phys. Chem. Chem. Phys. |volume=2016 |issue=18 |pages=17351–5 |doi=10.1039/c6cp02706g |pmid=27314425 |access-date=24 April 2017|bibcode=2016PCCP...1817351X |hdl=10138/224395 |s2cid=31224634 |hdl-access=free }}</ref>

===Atomic===
Lawrencium has three [[valence electron]]s: the 5f electrons are in the atomic core.<ref name=jensenlaw>{{cite web|url=http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/081.%20Periodic%20Table.pdf|last1=Jensen|first1=William B.|author-link=William B. Jensen|title=The Periodic Law and Table|date=2000|archive-url=https://web.archive.org/web/20201110113324/http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/081.%20Periodic%20Table.pdf |access-date=10 December 2022|archive-date=2020-11-10 }}</ref> In 1970, it was predicted that the ground-state [[electron configuration]] of lawrencium was [Rn]5f<sup>14</sup>6d<sup>1</sup>7s<sup>2</sup> (ground state [[term symbol]] <sup>2</sup>D<sub>3/2</sub>), per the [[Aufbau principle]] and conforming to the [Xe]4f<sup>14</sup>5d<sup>1</sup>6s<sup>2</sup> configuration of lawrencium's lighter homolog lutetium.<ref name="Silva16434">{{harvnb|Silva|2011|pp=1643–4}}</ref> But the next year, calculations were published that questioned this prediction, instead expecting an anomalous [Rn]5f<sup>14</sup>7s<sup>2</sup>7p<sup>1</sup> configuration.<ref name="Silva16434" /> Though early calculations gave conflicting results,<ref>{{cite journal|last1 = Nugent|first1 = L. J.|last2 = Vander Sluis|first2 = K. L.|last3 = Fricke|first3 = Burhard|last4 = Mann|first4 = J. B.|title = Electronic configuration in the ground state of atomic lawrencium|url = https://kobra.bibliothek.uni-kassel.de/bitstream/urn:nbn:de:hebis:34-2008091523764/1/Fricke_electronic_1974.pdf|archive-url = https://web.archive.org/web/20081219162209/https://kobra.bibliothek.uni-kassel.de/bitstream/urn:nbn:de:hebis:34-2008091523764/1/Fricke_electronic_1974.pdf|archive-date = December 19, 2008|journal = [[Physical Review|Phys. Rev. A]]|volume = 9|issue = 6|pages = 2270–72|date = 1974|doi = 10.1103/PhysRevA.9.2270|bibcode = 1974PhRvA...9.2270N}}</ref> more recent studies and calculations confirm the s<sup>2</sup>p suggestion.<ref>{{cite journal |last1 = Eliav |first1 = E. |last2 = Kaldor |first2= U. |last3 = Ishikawa |first3 = Y. |title = Transition energies of ytterbium, lutetium, and lawrencium by the relativistic coupled-cluster method |journal = [[Physical Review|Phys. Rev. A]]|volume = 52|issue = 1 |pages = 291–296 |date = 1995 |doi = 10.1103/PhysRevA.52.291|pmid = 9912247 |bibcode = 1995PhRvA..52..291E }}</ref><ref>{{cite journal|last = Zou|first = Yu|author2=Froese Fischer C. |title = Resonance Transition Energies and Oscillator Strengths in Lutetium and Lawrencium|journal = [[Physical Review Letters|Phys. Rev. Lett.]] |volume = 88|page = 183001|date = 2002|pmid=12005680|doi=10.1103/PhysRevLett.88.023001|bibcode = 2001PhRvL..88b3001M|issue = 2 |last3 = Uiterwaal|first3 = C.|last4 = Wanner|first4 = J.|last5 = Kompa|first5 = K.-L.| s2cid=18391594 |url = http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1011&context=physicsuiterwaal}}</ref> 1974 [[relativistic quantum chemistry|relativistic]] calculations concluded that the energy difference between the two configurations was small and that it was uncertain which was the ground state.<ref name="Silva16434" /> Later 1995 calculations concluded that the s<sup>2</sup>p configuration should be energetically favored, because the spherical s and p<sub>1/2</sub> [[atomic orbital|orbitals]] are nearest to the [[atomic nucleus]] and thus move quickly enough that their relativistic mass increases significantly.<ref name="Silva16434" />

In 1988, a team of scientists led by Eichler calculated that lawrencium's [[enthalpy of adsorption]] on metal sources would differ enough depending on its electron configuration that it would be feasible to carry out experiments to exploit this fact to measure lawrencium's electron configuration.<ref name="Silva16434" /> The s<sup>2</sup>p configuration was expected to be more [[volatility (chemistry)|volatile]] than the s<sup>2</sup>d configuration, and be more similar to that of the [[p-block]] element [[lead]]. No evidence for lawrencium being volatile was obtained and the lower limit for the enthalpy of adsorption of lawrencium on [[quartz]] or [[platinum]] was significantly higher than the estimated value for the s<sup>2</sup>p configuration.<ref name="Silva16434" />

[[File:First Ionization Energy blocks.svg|thumb|right|512px|First ionization energy ([[electronvolt|eV]]) plotted against [[atomic number]], in units [[Electronvolt|eV]]. Predicted values are used beyond rutherfordium (element 104). Lawrencium (element 103) has a very low first ionization energy, fitting the start of the d-block trend better than the end of the f-block trend before it.<ref name=JensenLr/>]]
In 2015, the first ionization energy of lawrencium was measured, using the isotope <sup>256</sup>Lr.<ref name="Sato"/> The measured value, {{nowrap|4.96{{su|p=+0.08|b=−0.07}} [[electronvolt|eV]]}}, agreed very well with the relativistic theoretical prediction of 4.963(15)&nbsp;eV, and also provided a first step into measuring the first ionization energies of the [[transactinide]]s.<ref name="Sato" /> This value is the lowest among all the lanthanides and actinides, and supports the s<sup>2</sup>p configuration as the 7p<sub>1/2</sub> electron is expected to be only weakly bound. As ionisation energies generally increase left to right in the f-block, this low value suggests that lutetium and lawrencium belong in the d-block (whose trend they follow) and not the f-block. That would make them the heavier congeners of [[scandium]] and [[yttrium]], rather than [[lanthanum]] and [[actinium]].<ref name="JensenLr">{{cite web|url=https://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/251.%20Lawrencium.pdf |title=Some Comments on the Position of Lawrencium in the Periodic Table |last1=Jensen |first1=W. B. |date=2015 |access-date=20 September 2015 |archive-url=https://web.archive.org/web/20151223091325/https://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/251.%20Lawrencium.pdf |archive-date=23 December 2015 }}</ref> Although some [[alkali metal]]-like behaviour has been predicted,<ref>{{cite web |url=http://www.rsc.org/chemistryworld/2015/04/lawrencium-experiment-could-shake-periodic-table |title=Lawrencium experiment could shake up periodic table |last1=Gunther |first1=Matthew |date=9 April 2015 |website=RSC Chemistry World |access-date=21 September 2015}}</ref> adsorption experiments suggest that lawrencium is trivalent like scandium and yttrium, not monovalent like the alkali metals.<ref name=insights>{{cite journal |last=Haire |first=R. G. |date=11 October 2007 |title=Insights into the bonding and electronic nature of heavy element materials |journal=Journal of Alloys and Compounds |volume=444–5 |pages=63–71 |doi=10.1016/j.jallcom.2007.01.103|url=https://zenodo.org/record/1259091 }}</ref> A lower limit on lawrencium's second ionization energy (&gt;13.3&nbsp;eV) was experimentally found in 2021.<ref>{{cite journal |last1=Kwarsick |first1=Jeffrey T. |last2=Pore |first2=Jennifer L. |first3=Jacklyn M. |last3=Gates |first4=Kenneth E. |last4=Gregorich |first5=John K. |last5=Gibson |first6=Jiwen |last6=Jian |first7=Gregory K. |last7=Pang |first8=David K. |last8=Shuh |date=2021 |title=Assessment of the Second-Ionization Potential of Lawrencium: Investigating the End of the Actinide Series with a One-Atom-at-a-Time Gas-Phase Ion Chemistry Technique |url= https://escholarship.org/uc/item/8mp9k4g0|journal=The Journal of Physical Chemistry A |volume=125 |issue=31 |pages=6818–6828 |doi=10.1021/acs.jpca.1c01961 |pmid=34242037 |bibcode=2021JPCA..125.6818K |osti=1844939 |s2cid=235785891 }}</ref>

Even though s<sup>2</sup>p is now known to be the ground-state configuration of the lawrencium atom, ds<sup>2</sup> should be a low-lying excited-state configuration, with an excitation energy variously calculated as 0.156&nbsp;eV, 0.165&nbsp;eV, or 0.626&nbsp;eV.<ref name=peculiar/><!--in the supplementary information--> As such lawrencium may still be considered to be a d-block element, albeit with an anomalous electron configuration (like [[chromium]] or [[copper]]), as its chemical behaviour matches expectations for a heavier analogue of lutetium.<ref name=Jensen2015/>

===Isotopes===
{{main|Isotopes of lawrencium}}

Fourteen isotopes of lawrencium are known, with [[mass number]] 251–262, 264, and 266; all are radioactive.<ref name="Silva1642">{{harvnb|Silva|2011|p=1642}}</ref><ref name="266Lr">{{Cite journal |title=<sup>48</sup>Ca + <sup>249</sup>Bk Fusion Reaction Leading to Element ''Z'' = 117: Long-Lived α-Decaying <sup>270</sup>Db and Discovery of <sup>266</sup>Lr |journal=Physical Review Letters |volume=112 |issue=17 |doi=10.1103/PhysRevLett.112.172501 |date=2014 |last1=Khuyagbaatar |first1=J. |last2=Yakushev |first2=A. |last3=Düllmann |first3=Ch. E. |last4=Ackermann |first4=D. |last5=Andersson |first5=L.-L. |last6=Asai |first6=M. |last7=Block |first7=M. |last8=Boll |first8=R. A. |last9=Brand |first9=H. |last10=Cox |first10=D. M. |last11=Dasgupta |first11=M. |last12=Derkx |first12=X. |last13=Di Nitto |first13=A. |last14=Eberhardt |first14=K. |last15=Even |first15=J. |last16=Evers |first16=M. |last17=Fahlander |first17=C. |last18=Forsberg |first18=U. |last19=Gates |first19=J. M. |last20=Gharibyan |first20=N. |last21=Golubev |first21=P. |last22=Gregorich |first22=K. E. |last23=Hamilton |first23=J. H. |last24=Hartmann |first24=W. |last25=Herzberg |first25=R.-D. |last26=Heßberger |first26=F. P. |last27=Hinde |first27=D. J. |last28=Hoffmann |first28=J. |last29=Hollinger |first29=R. |last30=Hübner |first30=A. |display-authors=1|bibcode = 2014PhRvL.112q2501K |pmid=24836239 |article-number=172501|url=http://lup.lub.lu.se/search/ws/files/2377958/4432321.pdf |hdl=1885/70327 |s2cid=5949620 |hdl-access=free }}</ref><ref name="255Db" /> Seven [[nuclear isomer]]s are known. The longest-lived isotope, <sup>266</sup>Lr, has a half-life of about ten hours and is one of the longest-lived [[superheavy element|superheavy]] isotopes known to date.<ref>{{cite magazine|author=Clara Moskowitz |author-link= Clara Moskowitz |url=http://www.scientificamerican.com/article/superheavy-element-117-island-of-stability/ |title=Superheavy Element 117 Points to Fabled "Island of Stability" on Periodic Table |magazine=Scientific American |date= May 7, 2014 |access-date=2014-05-08}}</ref> However, shorter-lived isotopes are usually used in chemical experiments because <sup>266</sup>Lr currently can only be produced as a final [[decay product]] of even heavier and harder-to-make elements: it was discovered in 2014 in the [[decay chain]] of <sup>294</sup>[[tennessine|Ts]].<ref name="Silva1642" /><ref name="266Lr" /> <sup>256</sup>Lr (half-life 27&nbsp;seconds) was used in the first chemical studies on lawrencium: currently, the longer-lived <sup>260</sup>Lr (half-life 2.7&nbsp;minutes) is usually used for this purpose.<ref name="Silva1642" /> After <sup>266</sup>Lr, the longest-lived isotopes are <sup>264</sup>Lr ({{val|4.8|2.2|1.3|u=h}}), <sup>262</sup>Lr (3.6&nbsp;h), and <sup>261</sup>Lr (44&nbsp;min).<ref name="Silva1642" /><ref name="unc">{{Cite web|url=http://www.nucleonica.net/unc.aspx|title=Nucleonica :: Web driven nuclear science|access-date=2014-08-19|archive-date=2011-02-24|archive-url=http://archive.wikiwix.com/cache/20110224033429/http://www.nucleonica.net/unc.aspx}}</ref>{{NUBASE2016|ref}} All other known lawrencium isotopes have half-lives under 5&nbsp;minutes, and the shortest-lived of them (<sup>251</sup>Lr) has a half-life of 24.4&nbsp;milliseconds.<ref name="255Db">{{cite thesis |last1=Leppänen |first1=A.-P. |title=Alpha-decay and decay-tagging studies of heavy elements using the RITU separator |year=2005 |pages=83–100 |publisher=University of Jyväskylä |isbn=978-951-39-3162-9 |issn=0075-465X |url=https://jyx.jyu.fi/bitstream/handle/123456789/13915/978-951-39-3162-9.pdf?sequence=1&isAllowed=y}}</ref><ref name="unc" />{{NUBASE2016|ref}}<ref name=251Lr>{{cite journal |last1=Huang |first1=T. |last2=Seweryniak |first2=D. |last3=Back |first3=B. B. |display-authors=et al. |title=Discovery of the new isotope <sup>251</sup>Lr: Impact of the hexacontetrapole deformation on single-proton orbital energies near the {{nowrap|Z {{=}} 100}} deformed shell gap |journal=Physical Review C |volume=106 |number=L061301 |date=2022 |doi=10.1103/PhysRevC.106.L061301|osti=1906168 |s2cid=254300224 }}</ref> The half-lives of lawrencium isotopes mostly increase smoothly from <sup>251</sup>Lr to <sup>266</sup>Lr, with a dip from <sup>257</sup>Lr to <sup>259</sup>Lr.<ref name="Silva1642" /><ref name="unc" />{{NUBASE2016|ref}}

==Preparation and purification==
Most isotopes of lawrencium can be produced by bombarding actinide ([[americium]] to [[einsteinium]]) targets with light ions (from [[boron]] to neon). The two most important isotopes, <sup>256</sup>Lr and <sup>260</sup>Lr, can be respectively produced by bombarding [[californium]]-249 with 70&nbsp;MeV [[boron]]-11 ions (producing lawrencium-256 and four [[neutron]]s) and by bombarding [[berkelium]]-249 with [[oxygen]]-18 (producing lawrencium-260, an alpha particle, and three neutrons).<ref name="Silva16423">{{harvnb|Silva|2011|pp=1642–3}}</ref> The two heaviest and longest-lived known isotopes, <sup>264</sup>Lr and <sup>266</sup>Lr, can only be produced at much lower yields as decay products of dubnium, whose progenitors are isotopes of moscovium and tennessine.

Both <sup>256</sup>Lr and <sup>260</sup>Lr have half-lives too short to allow a complete chemical purification process. Early experiments with <sup>256</sup>Lr therefore used rapid [[solvent extraction]], with the [[chelating agent]] [[thenoyltrifluoroacetone]] (TTA) dissolved in [[methyl isobutyl ketone]] (MIBK) as the [[organic phase]], and with the [[aqueous phase]] being buffered [[acetate]] solutions. Ions of different charge (+2, +3, or +4) will then extract into the organic phase under different [[pH]] ranges, but this method will not separate the trivalent actinides and thus <sup>256</sup>Lr must be identified by its emitted 8.24&nbsp;MeV alpha particles.<ref name="Silva16423" /> More recent methods have allowed rapid selective elution with α-HIB to take place in enough time to separate out the longer-lived isotope <sup>260</sup>Lr, which can be removed from the catcher foil with 0.05&nbsp;M&nbsp;[[hydrochloric acid]].<ref name="Silva16423" />

==See also==
{{Subject bar
|portal=Chemistry
|book1=Lawrencium
|book2=Actinides
|book3=Period 7 elements
|book4=Group 3 elements
|book5=Chemical elements (sorted&nbsp;alphabetically)
|book6=Chemical elements (sorted by number)
|commons=y
|wikt=y
|wikt-search=lawrencium
}}

== 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-->|article-number=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 book|doi=10.1007/978-94-007-0211-0_13|title=The Chemistry of the Actinide and Transactinide Elements|date=2011|isbn=978-94-007-0210-3|publisher=Springer |place=Netherlands|last=Silva |first= Robert J.|editor= Morss, Lester R.|editor2= Edelstein, Norman M.|editor3= Fuger, Jean |chapter=Chapter 13. Fermium, Mendelevium, Nobelium, and Lawrencium }}
* {{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|article-number=012001|doi=10.1088/1742-6596/420/1/012001|arxiv=1207.5700|bibcode=2013JPhCS.420a2001Z|s2cid=55434734|issn=1742-6588}}

==External links==
* {{cite web|url=http://www.nndc.bnl.gov/chart/|title=Chart of Nuclides|publisher=National Nuclear Data Center (NNDC)|access-date=2014-08-21|archive-date=2018-10-10|archive-url=https://web.archive.org/web/20181010070007/http://www.nndc.bnl.gov/chart/}}
* [http://periodic.lanl.gov/103.shtml Los Alamos National Laboratory's Chemistry Division: Periodic Table – Lawrencium]
* [http://www.periodicvideos.com/videos/103.htm Lawrencium] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)

{{Periodic table (navbox)}}

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[[Category:Lawrencium| ]]
[[Category:Chemical elements]]
[[Category:Transition metals]]
[[Category:Actinides]]
[[Category:Synthetic elements]]
[[Category:Chemical elements with hexagonal close-packed structure]]