Editing Protactinium (section)

==History==
[[File:Periodensystem_Mendelejews.jpg|thumb|left|upright=1.5|[[Dmitri Mendeleev]]'s 1871 periodic table with a gap for protactinium on the bottom row of the chart, between thorium and uranium]]
In 1871, [[Dmitri Mendeleev]] [[Mendeleev's predicted elements|predicted]] the existence of an element between [[thorium]] and [[uranium]].<ref name="Emsley" /> The actinide series was unknown at the time, so Mendeleev positioned [[uranium]] below [[tungsten]] in [[Group (periodic table) | group]] VI, and thorium below [[zirconium]] in group IV, leaving the space below [[tantalum]] in group V empty. Until the general acceptance of the [[actinide concept]] in the late 1940s, [[periodic table]]s were published with this structure.<ref>{{cite journal|doi = 10.1007/s10698-004-5959-9|title=A Revised Periodic Table: With the Lanthanides Repositioned|author=Laing, Michael |journal=[[Foundations of Chemistry]]|volume=7|issue=3|date=2005|page=203|s2cid=97792365}}</ref> For a long time, chemists searched for [[Mendeleev's predicted elements|eka]]-tantalum<ref group=note>The prefix "eka" is derived from the [[Sanskrit]] [[wikt:एक#Sanskrit | एक]], meaning "one" or "first." In chemistry, it was formerly used to denote an element one period below the element name following it.</ref> as an element with similar chemical properties to tantalum, making a discovery of protactinium nearly impossible. Tantalum's heavier analogue was later found to be the transuranic element [[dubnium]] – although dubnium is more chemically similar to protactinium, not tantalum.<ref name="Fessl">{{cite web |last1=Fessl |first1=Sophie |title=How Far Does the Periodic Table Go? |url=https://daily.jstor.org/how-far-does-the-periodic-table-go/ |publisher=JSTOR |access-date=9 January 2019|date=2019-01-02 }}</ref>

In 1900, [[William Crookes]] isolated protactinium as an intensely radioactive material from uranium; however, he could not characterize it as a new chemical element and thus named it uranium X (UX).<ref name="Emsley">{{cite book|title = Nature's Building Blocks: An A-Z Guide to the Elements|last = Emsley|first = John|publisher = Oxford University Press|orig-year = 2001|location = Oxford, England, UK|isbn = 978-0-19-850340-8|chapter = Protactinium|pages = [https://archive.org/details/naturesbuildingb0000emsl/page/347 347–349]|chapter-url = https://books.google.com/books?id=j-Xu07p3cKwC&pg=PA348|date = 2003|url = https://archive.org/details/naturesbuildingb0000emsl/page/347}}</ref><ref name="google">{{cite book|title=A Glossary of Terms in Nuclear Science and Technology|author=National Research Council (U.S.). Conference on Glossary of Terms in Nuclear Science and Technology|date=1957|publisher=American Society of Mechanical Engineers|url=https://books.google.com/books?id=-zgrAAAAYAAJ&pg=PA180|page=180|access-date=25 July 2015}}</ref><ref>{{cite journal|doi = 10.1098/rspl.1899.0120|last1 = Crookes|first1 = W.|title = Radio-Activity of Uranium|url = https://books.google.com/books?id=hmZDAAAAYAAJ&pg=PA409-IA6|journal = [[Proceedings of the Royal Society of London]]|volume = 66|issue = 424–433|pages = 409–423|date = 1899|s2cid = 93563820|url-access = subscription}}</ref><!--https://www.jstor.org/pss/96048 --> Crookes dissolved [[uranium nitrate]] in [[diethyl ether|ether]], and the residual aqueous phase contained most of the {{nuclide|Th|234}} and {{nuclide|Pa|234}}. His method was used into the 1950s to isolate {{nuclide|Th|234}} and {{nuclide|Pa|234}} from uranium compounds.<ref>{{cite journal|last1 = Johansson|first1 = Sven|title = Decay of UX1, UX2, and UZ|journal = [[Physical Review]]|volume = 96|pages = 1075–1080|date = 1954|doi = 10.1103/PhysRev.96.1075|issue = 4|bibcode = 1954PhRv...96.1075J }}</ref> Protactinium was first identified in 1913, when [[Kasimir Fajans]] and [[Oswald Helmuth Göhring]] encountered the isotope <sup>234m</sup>Pa during their studies of the decay chains of [[uranium-238]]: {{nuclide|U|238}} → {{nuclide|Th|234}} → {{nuclide|Pa|234m}} → {{nuclide|U|234}}. They named the new element "[[brevium]]" (from the Latin word ''brevis'', meaning brief or short) because of the short half-life of 1.16 minutes for {{nuclide|Pa|234m}} (uranium&nbsp;X2).<ref name="g1250">[[#Greenwood|Greenwood]], p. 1250</ref><ref name="g1254">[[#Greenwood|Greenwood]], p. 1254</ref><ref>{{cite journal|author = Fajans, K.|author2 = Gohring, O.|name-list-style = amp|title = Über die komplexe Natur des Ur X|journal = [[Naturwissenschaften]]|date = 1913|volume =1|pages = 339|url =http://www.digizeitschriften.de/no_cache/home/jkdigitools/loader/?tx_jkDigiTools_pi1%5BIDDOC%5D=201162&tx_jkDigiTools_pi1%5Bpp%5D=425 |doi = 10.1007/BF01495360|issue = 14|bibcode = 1913NW......1..339F |s2cid = 40667401}}</ref><ref>{{cite journal|author = Fajans, K.|author2 = Gohring, O.|name-list-style = amp |title = Über das Uran X<sub>2</sub>-das neue Element der Uranreihe|journal = [[Physikalische Zeitschrift]]|date = 1913|volume = 14|pages = 877–84}}</ref><ref name="Scerri">[[Eric Scerri]], ''A tale of seven elements,'' (Oxford University Press 2013) {{ISBN|978-0-19-539131-2}}, p.67–74</ref><ref name=PaIsoDisc>{{cite journal |url=https://deepblue.lib.umich.edu/bitstream/handle/2027.42/62921/244137a0.pdf |title=Discovery and Naming of the Isotopes of Element 91 |last1=Fajans |first1=K. |last2=Morris |first2=D. F. C. |date=1973 |journal=Nature |volume=244 |issue=5412 |pages=137–138 |doi=10.1038/244137a0|bibcode=1973Natur.244..137F |hdl=2027.42/62921 }}</ref> In 1917–18, two groups of scientists, [[Lise Meitner]] in collaboration with [[Otto Hahn]] of [[Germany]] and [[Frederick Soddy]] and John Cranston of [[Great Britain]], independently discovered another isotope, <sup>231</sup>Pa, having a much longer half-life of 32,760 years.<ref name="meitner" /><ref name="Scerri" /><ref>[https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.1918.0025 Soddy, F., Cranston, J.F. (1918) The parent of actinium]. Proceedings of the Royal Society A – Mathematical, Physical and Engineering Sciences 94: 384-403.</ref> Meitner changed the name "brevium" to ''protactinium'' as the new element was part of the decay chain of uranium-235 as the parent of actinium (from the {{langx|el|πρῶτος}} ''prôtos'', meaning "first, before").<ref>{{cite web |title=Protactinium - Element information : Chemistry in its element: protactinium |url=https://www.rsc.org/periodic-table/element/91/protactinium |website=www.rsc.org |publisher=[[Royal Society of Chemistry]] |access-date=20 October 2023 |quote=At this point Fajans withdrew the name brevium since the custom was to name an element according to longest-lived isotope. Meitner than chose the name protactinium.}}</ref> The [[International Union of Pure and Applied Chemistry|IUPAC]] confirmed this naming in 1949.<ref name="CRC" /><ref name="g1251">[[#Greenwood|Greenwood]], p. 1251</ref> The discovery of protactinium completed one of the last gaps in early versions of the periodic table, and brought fame to the involved scientists.<ref>Shea, William R. (1983) [https://books.google.com/books?id=W7xyvXc-hgEC&pg=PA213 Otto Hahn and the rise of nuclear physics], Springer, p. 213, {{ISBN|90-277-1584-X}}.</ref>

[[Aristid von Grosse]] produced 2&nbsp;milligrams of Pa<sub>2</sub>O<sub>5</sub> in 1927,<ref>{{cite journal|author = von Grosse, Aristid |title = Das Element 91; seine Eigenschaften und seine Gewinnung |pages = 233–245|journal = [[Berichte der deutschen chemischen Gesellschaft]]|doi = 10.1002/cber.19280610137|volume = 61|issue = 1|date = 1928}}</ref> and in 1934 first isolated elemental protactinium from 0.1&nbsp;milligrams of Pa<sub>2</sub>O<sub>5</sub>.<ref>{{cite journal|doi = 10.1002/ange.19340473706|title = Die technische Gewinnung des Protactiniums|date = 1934|last1 = Graue|first1 = G.|last2 = Käding|first2 = H.|journal = [[Angewandte Chemie]]|volume = 47|issue = 37|pages = 650–653|bibcode = 1934AngCh..47..650G}}</ref> He used two different procedures: in the first, protactinium oxide was irradiated by 35&nbsp;keV electrons in vacuum. In the other, called the [[crystal bar process|van Arkel–de Boer process]], the oxide was chemically converted to a [[halide]] ([[chloride]], [[bromide]] or [[iodide]]) and then reduced in a vacuum with an electrically heated metallic filament:<ref name="CRC" /><ref>{{cite journal| last1=Grosse| first1=A. V.| journal=[[Journal of the American Chemical Society]]| volume=56|pages=2200–2201| date=1934| doi=10.1021/ja01325a508| issue=10| title=Metallic Element 91| bibcode=1934JAChS..56R2200G}}</ref>

: 2 PaI<sub>5</sub> → 2 Pa + 5 I<sub>2</sub>

In 1961, the [[United Kingdom Atomic Energy Authority]] (UKAEA) produced 127&nbsp;grams of 99.9% pure protactinium-231 by processing 60&nbsp;tonnes of waste material in a 12-stage process, at a cost of about US$500,000.<ref name="CRC" /><ref name="Myasoedov" /> For many years, this was the world's only significant supply of protactinium, which was provided to various laboratories for scientific studies.<ref name="Emsley" /> The [[Oak Ridge National Laboratory]] in the US provided protactinium at a cost of about US$280/gram.<ref>{{cite web |url=https://periodic.lanl.gov/91.shtml |title=Periodic Table of Elements: Protactinium |access-date=2013-03-21 |publisher=[[Los Alamos National Laboratory]] |url-status=dead<!-- information subsequently removed --> |archive-url=https://web.archive.org/web/20110928025549/http://periodic.lanl.gov/91.shtml |archive-date=28 September 2011}}</ref>