Editing Protactinium (section)

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{{Infobox protactinium}}
'''Protactinium''' is a [[chemical element]]; it has [[chemical symbol|symbol]] '''Pa''' and [[atomic number]] 91. It is a dense, [[radioactive]], silvery-gray [[actinide]] metal which readily reacts with [[oxygen]], water vapor, and inorganic [[acid]]s. It forms various [[chemical compound]]s, in which protactinium is usually present in the [[oxidation state]] +5, but it can also assume +4 and even +3 or +2 states. Concentrations of protactinium in the Earth's crust are typically a few parts per trillion, but may reach up to a few parts per million in some [[uraninite]] ore deposits. Because of its scarcity, high radioactivity, and high toxicity, there are currently no uses for protactinium outside scientific research, and for this purpose, protactinium is mostly extracted from [[spent nuclear fuel]].

The element was first identified in 1913 by [[Kazimierz Fajans]] and [[Oswald Helmuth Göhring]] and named "brevium" because of the short [[half-life]] of the specific [[isotope]] studied, [[Nuclear isomer|<sup>234m</sup>Pa]]. A more stable isotope of protactinium, <sup>231</sup>Pa, was discovered in 1917/18 by [[Lise Meitner]] in collaboration with [[Otto Hahn]], and they named the element protactinium.<ref name="meitner">{{cite journal | last=Meitner | first=Lise | title=Die Muttersubstanz des Actiniums, Ein Neues Radioaktives Element von Langer Lebensdauer | journal=Zeitschrift für Elektrochemie und angewandte physikalische Chemie | volume=24 | issue=11–12 | date=1918 | issn=0372-8323 | doi=10.1002/bbpc.19180241107 | pages=169–173}}</ref> In 1949, the [[IUPAC]] chose the name "protactinium" and confirmed Hahn and Meitner as its discoverers. The new name meant "(nuclear) [[precursor (chemistry)|precursor]] of [[actinium]],"<ref>{{cite web |title=Protactinium |url=http://hpschapters.org/northcarolina/NSDS/Protactinium.pdf |website=Human Health Fact Sheet |publisher=ANL (Argonne National Laboratory) |access-date=4 September 2023 |date=November 2001 |quote=The name comes from the Greek work protos (meaning first) and the element actinium, because protactinium is the precursor of actinium.}}</ref> suggesting that actinium is a product of radioactive decay of protactinium. [[John Arnold Cranston]] (working with [[Frederick Soddy]] and [[Ada Hitchins]]) is also credited with discovering the most stable isotope in 1915, but he delayed his announcement due to being called for service in the [[First World War]].<ref>[http://www.universitystory.gla.ac.uk/biography/?id=WH3023&type=P John Arnold Cranston] {{Webarchive|url=https://web.archive.org/web/20200311015550/http://www.universitystory.gla.ac.uk/biography/?id=WH3023&type=P |date=11 March 2020 }}. [[University of Glasgow]]</ref>

The longest-lived and most abundant (nearly 100%) naturally occurring [[isotope]] of protactinium, <sup>231</sup>Pa, has a [[half-life]] of 32,760 years and is a decay product of [[uranium-235]]. Much smaller trace amounts of the short-lived <sup>234</sup>Pa and its [[nuclear isomer]] <sup>234m</sup>Pa occur in the decay chain of [[uranium-238]]. <sup>233</sup>Pa occurs as a result of the decay of [[thorium]]-233 as part of the chain of events necessary to produce [[uranium-233]] by neutron irradiation of <sup>232</sup>Th. It is an undesired intermediate product in [[Thorium-based nuclear power | thorium-based]] [[nuclear reactor]]s, and is therefore removed from the active zone of the reactor during the breeding process. Ocean science uses the element to understand the ancient ocean's geography: analysis of the relative concentrations of various uranium, thorium, and protactinium isotopes in water and minerals is used in [[radiometric dating]] of [[sediment]]s up to 175,000 years old, and in modeling of various geological processes.<ref>{{cite journal | last1 = Negre | first1 = César | display-authors = etal | year = 2010| title = Reversed flow of Atlantic deep water during the Last Glacial Maximum | url = https://www.pure.ed.ac.uk/ws/files/11751410/ReversedATlantic_Deep.pdf| journal = Nature | volume = 468 | issue = 7320| pages = 84–8 | doi = 10.1038/nature09508 | pmid = 21048764 | bibcode = 2010Natur.468...84N }}</ref>