Editing Actinide (section)

=== Neptunium and above ===
Neptunium (named for the planet [[Neptune]], the next [[planet]] out from Uranus, after which uranium was named) was discovered by [[Edwin McMillan]] and [[Philip H. Abelson]] in 1940 in [[Berkeley, California]].<ref>{{cite journal|doi=10.1103/PhysRev.57.1185.2|title=Radioactive Element 93|year=1940|author=Edwin McMillan|journal=Physical Review|volume=57|pages=1185–1186|last2=Abelson|first2=Philip|issue=12|bibcode=1940PhRv...57.1185M|doi-access=free}}</ref> They produced the <sup>239</sup>Np isotope (half-life 2.4 days) by bombarding uranium with slow [[neutron]]s.<ref name=g1251 /> It was the first [[transuranium element]] produced synthetically.<ref name="Himiya neptuniya">{{cite book|title=Analytical chemistry of neptunium|editor=V.A. Mikhailov|place=Moscow|publisher=Nauka|year=1971}}</ref>

[[File:Glenn Seaborg - 1964.jpg|thumb|[[Glenn T. Seaborg]] and his group at the [[University of California at Berkeley]] synthesized Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No and element 106, which was later named [[seaborgium]] in his honor while he was still living. They also synthesized more than a hundred actinide isotopes.]]

Transuranium elements do not occur in sizeable quantities in nature and are commonly synthesized via [[nuclear reaction]]s conducted with nuclear reactors. For example, under irradiation with reactor neutrons, [[uranium-238]] partially converts to [[plutonium-239]]:
: <math chem>\ce{{^{238}_{92}U} + {}^{1}_{0}n -> {}^{239}_{92}U ->[\beta^-] [23.5\ \ce{min}] {}^{239}_{93}Np ->[\beta^-] [2.3\ \ce{days}] {}^{239}_{94}Pu} \left( \ce{->[\alpha] [2.4\cdot 10^4\ \ce{years}]} \right) \ce{{^{235}_{92}U}}</math>

This synthesis reaction was used by Fermi and his collaborators in their design of the reactors located at the [[Hanford Site]], which produced significant amounts of plutonium-239 for the nuclear weapons of the [[Manhattan Project]] and the United States' post-war nuclear arsenal.<ref>{{cite book|last=Hanford Cultural Resources Program, US Department of Energy|title=Hanford Site Historic District: History of the Plutonium Production Facilities, 1943–1990|publisher=Battelle Press|year=2002|location=Columbus OH|isbn=978-1-57477-133-6|pages=1.22–1.27|url=http://www.osti.gov/scitech/servlets/purl/807939|doi=10.2172/807939 }}</ref>

Actinides with the highest mass numbers are synthesized by bombarding uranium, plutonium, curium and californium with [[ion]]s of nitrogen, oxygen, carbon, neon or boron in a [[particle accelerator]]. Thus [[nobelium]] was produced by bombarding uranium-238 with [[neon-22]] as
: <chem>_{92}^{238}U + _{10}^{22}Ne -> _{102}^{256}No + 4_0^1n</chem>.

The first isotopes of transplutonium elements, [[americium-241]] and [[curium-242]], were synthesized in 1944 by [[Glenn T. Seaborg]], [[Ralph A. James]] and [[Albert Ghiorso]].<ref>{{cite book|title=The New Chemistry: A Showcase for Modern Chemistry and Its Applications|author=Nina Hall|publisher=Cambridge University Press|year=2000|pages=8–9|isbn=978-0-521-45224-3|url=https://archive.org/details/newchemistry00hall|url-access=registration}}</ref> Curium-242 was obtained by bombarding plutonium-239 with 32-MeV α-particles:
: <chem>_{94}^{239}Pu + _2^4He -> _{96}^{242}Cm + _0^1n</chem>.

The americium-241 and curium-242 isotopes also were produced by irradiating plutonium in a nuclear reactor. The latter element was named after [[Marie Curie]] and her husband [[Pierre Curie|Pierre]] who are noted for discovering [[radium]] and for their work in [[radioactivity]].<ref>Myasoedov, p. 8</ref>

Bombarding curium-242 with α-particles resulted in an isotope of californium [[Californium-245|<sup>245</sup>Cf]] in 1950, and a similar procedure yielded [[berkelium-243]] from americium-241 in 1949.<ref>{{cite journal|first1=S. G.|last1=Thompson|first2=A.|last2=Ghiorso|author-link2=Albert Ghiorso|first3=G. T.|last3=Seaborg|author-link3=Glenn T. Seaborg|title=Element 97|journal=Phys. Rev.|year=1950|volume=77|issue=6|pages=838–839|doi=10.1103/PhysRev.77.838.2|bibcode=1950PhRv...77..838T |doi-access=free}}</ref> The new elements were named after [[Berkeley, California]], by analogy with its [[lanthanide]] [[Homologous series|homologue]] [[terbium]], which was named after the village of [[Ytterby]] in Sweden.<ref>{{cite journal|first1 = S. G.|last1=Thompson|first2=A.|last2=Ghiorso|author-link2=Albert Ghiorso|first3=G. T.|last3=Seaborg|author-link3=Glenn T. Seaborg|title=The New Element Berkelium (Atomic Number 97)|journal=Phys. Rev.|year=1950|volume=80|pages=781–789|doi=10.1103/PhysRev.80.781|issue=5|bibcode=1950PhRv...80..781T|url=https://digital.library.unt.edu/ark:/67531/metadc894817/}}</ref>

In 1945, B. B. Cunningham obtained the first bulk chemical compound of a transplutonium element, namely [[Americium(III) hydroxide|americium hydroxide]].<ref>Wallace W. Schulz (1976) [http://www.osti.gov/bridge/purl.cover.jsp;jsessionid=99C379B4BBA56BB186AAD989333D2B5E?purl=/7232133-fyKvqE/ The Chemistry of Americium], U.S. Department of Commerce, p. 1</ref> Over the few years, milligram quantities of americium and microgram amounts of curium were accumulated that allowed production of isotopes of berkelium<ref>{{cite journal|last1=Thompson|first1=S.|last2=Ghiorso|first2=A.|last3=Seaborg|first3=G.|title=Element 97|journal=Physical Review|volume=77|pages=838–839|year=1950|doi=10.1103/PhysRev.77.838.2|issue=6|bibcode=1950PhRv...77..838T|doi-access=free}}</ref><ref>{{cite journal|last1=Thompson|first1=S.|last2=Ghiorso|first2=A.|last3=Seaborg|first3=G.|title=The New Element Berkelium (Atomic Number 97)|journal=Physical Review|volume=80|pages=781–789|year=1950|doi=10.1103/PhysRev.80.781|issue=5|bibcode=1950PhRv...80..781T|url=https://digital.library.unt.edu/ark:/67531/metadc894817/}}</ref> and californium.<ref>{{cite journal|author1=S. G. Thompson|author2=K. Street Jr.|author3=A. Ghiorso|author4=G. T. Seaborg|title=Element 98|journal=[[Physical Review]]|year=1950|volume=78|pages=298–299|doi=10.1103/PhysRev.78.298.2|url=http://repositories.cdlib.org/cgi/viewcontent.cgi?article=7072&context=lbnl|issue=3|bibcode=1950PhRv...78..298T|doi-access=free}}</ref><ref>{{cite journal|author1=S. G. Thompson|author2=K. Street Jr.|author3=A. Ghiorso|author4=G. T. Seaborg| title=The New Element Californium (Atomic Number 98)|journal=Physical Review|year=1950|volume=80|pages=790–796|doi=10.1103/PhysRev.80.790|url=http://www.osti.gov/accomplishments/documents/fullText/ACC0050.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.osti.gov/accomplishments/documents/fullText/ACC0050.pdf |archive-date=2022-10-09 |url-status=live|issue=5|bibcode=1950PhRv...80..790T}}</ref><ref>{{cite journal|author1=K. Street Jr.|author2=S. G. Thompson|author3=G. T. Seaborg|title=Chemical Properties of Californium|journal=[[J. Am. Chem. Soc.]]|year=1950|volume=72|pages=4832–4835|doi=10.1021/ja01166a528|url=http://handle.dtic.mil/100.2/ADA319899|archive-url=http://arquivo.pt/wayback/20160515073629/http://handle.dtic.mil/100.2/ADA319899|url-status=dead|archive-date=15 May 2016|issue=10|bibcode=1950JAChS..72R4832S |hdl=2027/mdp.39015086449173|access-date=23 October 2010}}</ref> Sizeable amounts of these elements were produced in 1958,<ref>S. G. Thompson and B. B. Cunningham (1958) [https://escholarship.org/uc/item/1wh7c44z "First Macroscopic Observations of the Chemical Properties of Berkelium and Californium"], supplement to Paper P/825 presented at the Second Intl. Conf., Peaceful Uses Atomic Energy, Geneva</ref> and the first californium compound (0.3&nbsp;μg of CfOCl) was obtained in 1960 by B. B. Cunningham and J. C. Wallmann.<ref>Darleane C. Hoffman, Albert Ghiorso, Glenn Theodore Seaborg (2000) ''The transuranium people: the inside story'', Imperial College Press, {{ISBN|1-86094-087-0}}, pp. 141–142</ref>

Einsteinium and fermium were identified in 1952–1953 in the fallout from the "[[Ivy Mike]]" nuclear test (1 November 1952), the first successful test of a hydrogen bomb. Instantaneous exposure of uranium-238 to a large neutron flux resulting from the explosion produced heavy isotopes of uranium, which underwent a series of [[beta decay]]s to nuclides such as [[einsteinium-253]] and [[fermium-255]]. The discovery of the new elements and the new data on neutron capture were initially kept secret on the orders of the US&nbsp;military until 1955 due to [[Cold War]] tensions.<ref name="PR1955" /><ref name="PhysRev.99.1048">{{cite journal|title=New Elements Einsteinium and Fermium, Atomic Numbers 99 and 100|author1=A. Ghiorso|author2=S. G. Thompson|author3=G. H. Higgins|author4=G. T. Seaborg|author5=M. H. Studier|author6=P. R. Fields|author7=S. M. Fried|author8=H. Diamond|author9=J. F. Mech|author10=G. L. Pyle|author11=J. R. Huizenga|author12=A. Hirsch|author13=W. M. Manning|author14=C. I. Browne|author15=H. L. Smith|author16=R. W. Spence|journal=Phys. Rev.|volume=99|issue=3|doi=10.1103/PhysRev.99.1048|pages=1048–1049|year=1955|bibcode=1955PhRv...99.1048G|url=https://digital.library.unt.edu/ark:/67531/metadc889467/|doi-access=free}}</ref> Nevertheless, the Berkeley team were able to prepare einsteinium and fermium by civilian means, through the neutron bombardment of plutonium-239, and published this work in 1954 with the disclaimer that it was not the first studies that had been carried out on those elements.<ref>{{cite journal|journal=Physical Review|volume=93|year=1954|title=Transcurium Isotopes Produced in the Neutron Irradiation of Plutonium|author1=S. Thompson|author2=A. Ghiorso|author3=B. G. Harvey|author4=G. R. Choppin|doi=10.1103/PhysRev.93.908|page=908|issue=4|bibcode=1954PhRv...93..908T|url=https://digital.library.unt.edu/ark:/67531/metadc1016991/|doi-access=free}}</ref><ref>{{Cite journal|author1=G. R. Choppin|author2=S. G. Thompson|author3=A. Ghiorso|author4=B. G. Harvey|title=Nuclear Properties of Some Isotopes of Californium, Elements 99 and 100|journal=Physical Review|volume=94|issue=4|pages=1080–1081|year=1954|doi=10.1103/PhysRev.94.1080|bibcode=1954PhRv...94.1080C|doi-access=free}}</ref> The "Ivy Mike" studies were declassified and published in 1955.<ref name="PhysRev.99.1048" /> The first significant (submicrogram) amounts of einsteinium were produced in 1961 by Cunningham and colleagues, but this has not been done for fermium yet.<ref>{{cite journal|author=Albert Ghiorso|author-link=Albert Ghiorso|year=2003|title=Einsteinium and Fermium|journal=Chemical and Engineering News|url=http://pubs.acs.org/cen/80th/einsteiniumfermium.html|volume=81|issue=36}}</ref>

The first isotope of mendelevium, [[mendelevium-256|<sup>256</sup>Md]] (half-life 87 min), was synthesized by Albert Ghiorso, Glenn T. Seaborg, [[Gregory Robert Choppin]], Bernard G. Harvey and [[Stanley Gerald Thompson]] when they bombarded an <sup>253</sup>Es target with [[alpha particle]]s in the 60-inch [[cyclotron]] of [[Berkeley Radiation Laboratory]]; this was the first isotope of any element to be synthesized one atom at a time.<ref>{{cite book|doi=10.1103/PhysRev.98.1518|url=https://books.google.com/books?id=e53sNAOXrdMC&pg=PA101|isbn=978-981-02-1440-1|title=New Element Mendelevium, Atomic Number 101|year=1955|author1=A. Ghiorso |author2=B. Harvey |author3=G. Choppin|author4=S. Thompson|author5=G. Seaborg|journal=Physical Review|volume=98|pages=1518–1519|issue=5|bibcode=1955PhRv...98.1518G}}</ref>

There were several attempts to obtain isotopes of nobelium by Swedish (1957) and American (1958) groups, but the first reliable result was the synthesis of [[Nobelium-256|<sup>256</sup>No]] by the Russian group of [[Georgy Flyorov]] in 1965, as acknowledged by the [[IUPAC]] in 1992. In their experiments, Flyorov et al. bombarded uranium-238 with neon-22.<ref name=g1252 />

In 1961, Ghiorso et al. obtained the first isotope of lawrencium by irradiating californium (mostly [[californium-252]]) with [[boron-10]] and [[boron-11]] ions.<ref name=g1252 /> The [[mass number]] of this isotope was not clearly established (possibly 258 or 259) at the time. In 1965, [[Lawrencium-256|<sup>256</sup>Lr]] was synthesized by Flyorov et al. from [[Americium-243|<sup>243</sup>Am]] and [[oxygen-18|<sup>18</sup>O]]. Thus IUPAC recognized the nuclear physics teams at Dubna and Berkeley as the co-discoverers of lawrencium.