Editing Radon (section)

== History and etymology ==
[[Image:Radon apparatus.png|thumb|upright|Apparatus used by Ramsay and Whytlaw-Gray to isolate radon. '''M''' is a [[capillary tube]], where approximately 0.1&nbsp;mm<sup>3</sup> were isolated. Radon mixed with hydrogen entered the evacuated system through siphon '''A'''; mercury is shown in black.]]

Radon was discovered in 1899 by [[Ernest Rutherford]] and [[Robert B. Owens]] at [[McGill University]] in [[Montreal]].<ref name="Rutherford" /> It was the fifth radioactive element to be discovered, after uranium, thorium, radium, and polonium.<ref>{{cite journal |title=Discovery of Radon |journal=[[Nature (journal)|Nature]] |volume=179 |page=912 |date=1957 |author=Partington, J. R. |doi=10.1038/179912a0 |issue=4566 |bibcode=1957Natur.179..912P|s2cid=4251991 |doi-access=free }}</ref><ref name="D2">{{cite web |url=http://chemistry.about.com/library/weekly/aa030303a.htm |title=Timeline of Element Discovery |date=2008 |publisher=[[The New York Times Company]] |access-date=2008-02-28 |archive-date=2009-02-08 |archive-url=https://web.archive.org/web/20090208130034/http://chemistry.about.com/library/weekly/aa030303a.htm |url-status=dead }}</ref><ref>{{Unbulleted list citebundle|{{cite journal |doi=10.1080/10256018808623931 |title=Zur Entdeckungsgeschichte des Radons |language=de |date=1988 |last1=Schüttmann |first1=W. |journal=Isotopenpraxis Isotopes in Environmental and Health Studies |volume=24 |issue=4 |page=158|bibcode=1988IIEHS..24..158S }}|{{cite journal |doi=10.1118/1.598902 |title=Rutherford, the Curies, and Radon |date=2000 |last1=Brenner |first1=David J. |journal=[[Medical Physics (journal)|Medical Physics]] |volume=27 |issue=3 |page=618 |pmid=10757614 |bibcode=2000MedPh..27..618B }}}}</ref> In 1899, [[Pierre Curie|Pierre]] and [[Marie Curie]] observed that the gas emitted by radium remained radioactive for a month.<ref>{{cite journal |journal=Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences |author=Curie, P. |author2=Curie, Mme. Marie |title=Sur la radioactivite provoquee par les rayons de Becquerel |language=fr |volume=129 |date= 1899 |pages=714–6}}</ref> Later that year, Rutherford and Owens noticed variations when trying to measure radiation from thorium oxide.<ref name="Rutherford">{{cite journal |author=Rutherford, E. |author2=Owens, R. B. |title=Thorium and uranium radiation |journal=Trans. R. Soc. Can. |volume=2 |date=1899 |pages=9–12}}: "The radiation from thorium oxide was not constant, but varied in a most capricious manner", whereas "All the compounds of Uranium give out a radiation which is remarkably constant."</ref> Rutherford noticed that the compounds of thorium continuously emit a radioactive gas that remains radioactive for several minutes, and called this gas "emanation" (from {{langx|la|emanare}}, to flow out, and {{lang|la|emanatio}}, expiration),<ref>{{cite journal |author=Rutherford, E. |title=A radioactive substance emitted from thorium compounds |url=http://www.chemteam.info/Chem-History/Rutherford-half-life.html |journal=[[Phil. Mag.]] |volume=40 |date=1900 |issue=296 |pages=1–4|doi=10.1080/14786440009463821 }}</ref> and later "thorium emanation" ("Th Em"). In 1900, [[Friedrich Ernst Dorn]] reported some experiments in which he noticed that radium compounds emanate a radioactive gas he named "radium emanation" ("Ra Em").<ref>{{Unbulleted list citebundle|{{cite journal |journal=Abhandlungen der Naturforschenden Gesellschaft zu Halle |volume=22 |author=Dorn, Friedrich Ernst |page=155 |title=Über die von radioaktiven Substanzen ausgesandte Emanation |language=de |location=Stuttgart |date=1900 |url=http://publikationen.ub.uni-frankfurt.de/files/17242/E001458681_a.pdf}}|{{Cite journal |title = Die von radioactiven Substanzen ausgesandte Emanation |language=de |author = Dorn, F. E. |journal = Abhandlungen der Naturforschenden Gesellschaft zu Halle |date = 1900 |volume = 23 |pages = 1–15 |url=http://publikationen.ub.uni-frankfurt.de/files/17242/E001458681_a.pdf}}}}</ref> In 1901, Rutherford and [[Harriet Brooks]] demonstrated that the emanations are radioactive, but credited the Curies for the discovery of the element.<ref>{{cite journal |author=Rutherford, E. |author2=Brooks, H. T. |title=The new gas from radium |journal=Trans. R. Soc. Can. |volume=7 |date=1901 |pages=21–25}}</ref> In 1903, similar emanations were observed from actinium by [[André-Louis Debierne]], and were called "actinium emanation" ("Ac Em").<ref>{{Unbulleted list citebundle|{{cite journal |author=Giesel, Fritz |title=Über den Emanationskörper aus Pechblende und über Radium |language=de |journal=[[Chemische Berichte]] |volume=36 |date=1903 |page=342 |doi=10.1002/cber.19030360177 |url=https://zenodo.org/record/1426068 }}|{{cite journal |author=Debierne, André-Louis |title=Sur la radioactivite induite provoquee par les sels d'actinium |language=fr |journal=Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences |volume=136 |date=1903 |page=446 |url=http://gallica.bnf.fr/ark:/12148/bpt6k3091c/f446.table}}}}</ref>

Several shortened names were soon suggested for the three emanations: ''exradio'', ''exthorio'', and ''exactinio'' in 1904;<ref name="ramsay1904">{{cite journal |author=Ramsay, Sir William |author2=Collie, J. Norman |title=The Spectrum of the Radium Emanation |journal=[[Proceedings of the Royal Society]] |volume=73 |date= 1904 |pages=470–476 |doi=10.1098/rspl.1904.0064 |issue=488–496 |doi-access=free }}</ref> ''radon'' (Ro), ''thoron'' (To), and ''akton'' or ''acton'' (Ao) in 1918;<ref>{{cite journal |author=Schmidt, Curt |title=Periodisches System und Genesis der Elemente |language=de |journal=[[Zeitschrift für anorganische und allgemeine Chemie]] |volume=103 |date=1918 |pages=79–118 |doi=10.1002/zaac.19181030106 |url=https://zenodo.org/record/1428158 }}</ref> ''radeon'', ''thoreon'', and ''actineon'' in 1919,<ref>{{cite journal |title=Matière et lumière. Essai de synthèse de la mécanique chimique |language=fr |journal=[[Annales de Physique]] |series=IX |volume=11 |date=1919 |pages=5–108 |author=Perrin, Jean |doi=10.1051/anphys/191909110005 |author-link=Jean Baptiste Perrin |url=https://books.google.com/books?id=Vc9XAAAAYAAJ&q=rad%C3%A9on }}</ref> and eventually ''radon'', ''thoron'', and ''actinon'' in 1920.<ref>{{cite journal |author=Adams, Elliot Quincy |title=The Independent Origin of Actinium |journal=[[Journal of the American Chemical Society]] |volume=42 |date=1920 |page=2205 |doi=10.1021/ja01456a010 |issue=11 |bibcode=1920JAChS..42.2205A |url=https://zenodo.org/record/1428836 }}</ref> (The name radon is not related to that of the Austrian mathematician [[Johann Radon]].) The likeness of the [[Spectral line|spectra]] of these three gases with those of argon, krypton, and xenon, and their observed chemical inertia led Sir [[William Ramsay]] to suggest in 1904 that the "emanations" might contain a new element of the noble-gas family.<ref name="ramsay1904" />

In 1909, Ramsay and [[Robert Whytlaw-Gray]] isolated radon and determined its [[Melting point|melting temperature]] and [[critical point (thermodynamics)|critical point]].<ref name="ramsay-melting"/> Because it does not conform to expected periodic trends, their obtained melting point (the only experimental value) was questioned in 1925 by [[Friedrich Paneth]] and E. Rabinowitsch, but ''ab initio'' Monte Carlo simulations from 2018 agree almost exactly with Ramsay and Gray's result.<ref>{{cite journal |last1=Smits |first1=Odile R. |last2=Jerabek |first2=Paul |last3=Pahl |first3=Elke |last4=Schwerdtfeger |first4=Peter |date=2018 |title=A Hundred-Year-Old Experiment Re-evaluated: Accurate Ab Initio Monte Carlo Simulations of the Melting of Radon |url= |journal=Angewandte Chemie |volume=57 |issue=31 |publisher= |pages=9961–9964 |doi=10.1002/anie.201803353 |access-date=}}</ref> In 1910, they determined its [[density]] (that showed it was the heaviest known gas) and its position in the periodic table.<ref name="ramsay-melting">{{cite journal |title=Some Physical Properties of Radium Emanation |author=R. W. Gray |author2=W. Ramsay |journal=[[J. Chem. Soc. Trans.]] |volume=1909 |pages=1073–1085 |date=1909|doi=10.1039/CT9099501073 |url=https://zenodo.org/record/1529110 }}</ref> They wrote that "{{Lang|fr|L'expression ''l'émanation du radium'' est fort incommode|italic=unset}}" ("the expression 'radium emanation' is very awkward") and suggested the new name niton (Nt) (from {{langx|la|nitens}}, shining) to emphasize the radioluminescence property,<ref name="ramsay">{{cite journal |title=La densité de l'emanation du radium |language=fr |author=Ramsay, W. |author2=Gray, R. W. |journal=[[Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences]] |volume=151 |pages=126–128 |date=1910 |url=http://gallica.bnf.fr/ark:/12148/bpt6k31042/f126.table}}</ref> and in 1912 it was accepted by the [[Commission on Isotopic Abundances and Atomic Weights|International Commission for Atomic Weights]]. In 1923, the International Committee for Chemical Elements and [[International Union of Pure and Applied Chemistry]] (IUPAC) chose the name of the most stable isotope, radon, as the name of the element. The isotopes thoron and actinon were later renamed [[Radon-220|{{sup|220}}Rn]] and {{sup|219}}Rn. This has caused some confusion in the literature regarding the element's discovery as while Dorn had discovered radon the isotope, he was not the first to discover radon the element.<ref name="ThorntonBurdette" />

As late as the 1960s, the element was also referred to simply as ''emanation''.<ref>{{cite journal |doi=10.1016/0022-1902(65)80255-X |date=1965 |title=Some physical and chemical properties of element 118 (Eka-Em) and element 86 (Em) |author=Grosse, A. V. |journal=[[Journal of Inorganic and Nuclear Chemistry]] |volume=27 |page=509 |issue=3}}</ref> The first synthesized compound of radon, radon fluoride, was obtained in 1962.<ref>{{cite journal |author=Fields, Paul R. |author2=Stein, Lawrence |author3=Zirin, Moshe H. |title=Radon Fluoride |journal=[[J. Am. Chem. Soc.]] |date=1962 |volume=84 |page=4164 |doi=10.1021/ja00880a048 |issue=21|bibcode=1962JAChS..84.4164F }}</ref> Even today, the word ''radon'' may refer to either the element or its isotope <sup>222</sup>Rn, with ''thoron'' remaining in use as a short name for <sup>220</sup>Rn to stem this ambiguity. The name ''actinon'' for <sup>219</sup>Rn is rarely encountered today, probably due to the short half-life of that isotope.<ref name="ThorntonBurdette">{{cite journal |last1=Thornton |first1=Brett F. |last2=Burdette |first2=Shawn C. |date=22 August 2013 |title=Recalling radon's recognition |journal=[[Nature Chemistry]] |volume=5 |issue=9 |pages=804 |doi=10.1038/nchem.1731 |pmid=23965684 |bibcode=2013NatCh...5..804T |doi-access=free }}</ref>

The danger of high exposure to radon in mines, where exposures can reach 1,000,000&nbsp;[[Becquerel|Bq]]/m<sup>3</sup>, has long been known. In 1530, [[Paracelsus]] described a wasting disease of miners, the ''mala metallorum'', and [[Georg Agricola]] recommended ventilation in mines to avoid this mountain sickness (''Bergsucht'').<ref name="Masse-2002">{{Unbulleted list citebundle|{{Cite web|last=Masse |first=Roland |date=2002 |archive-url=https://web.archive.org/web/20071009164542/http://www.radon-france.com/pdf/historique.pdf |url=http://www.radon-france.com/pdf/historique.pdf |archive-date=October 9, 2007 |title=Le radon, aspects historiques et perception du risque |website=radon-france.com |language=fr |trans-title=Radon, historical aspects and perception of risk}}|{{Cite web|archive-url=https://web.archive.org/web/20090116120009/http://www.atsdr.cdc.gov/csem/radon/whosat_risk.html |url=http://www.atsdr.cdc.gov/csem/radon/whosat_risk.html |title=Radon Toxicity: Who is at Risk? |publisher=Agency for Toxic Substances and Disease Registry |date=2000 |archive-date=January 16, 2009}}}}</ref> In 1879, this condition was identified as lung cancer by Harting and Hesse in their investigation of miners from Schneeberg, Germany.<ref name="George-2008">{{Cite journal |last1=George |first1=A. C. |last2=Paschoa |first2=Anselmo Salles |last3=Steinhäusler |first3=Friedrich |date=2008 |title=World History Of Radon Research And Measurement From The Early 1900's To Today |url=https://pubs.aip.org/aip/acp/article-abstract/1034/1/20/860949/World-History-Of-Radon-Research-And-Measurement?redirectedFrom=fulltext |journal=AIP Conference Proceedings |publisher=AIP |volume=1034 |pages=20–33 |doi=10.1063/1.2991210|bibcode=2008AIPC.1034...20G }}</ref> The first major studies with radon and health occurred in the context of uranium mining in the [[Jáchymov|Joachimsthal]] region of [[Bohemia]].<ref>{{Cite book|last=Proctor |first=Robert N. |title=The Nazi War on Cancer |publisher=Princeton University Press |date=2000 |page= 99 |isbn=0-691-07051-2}}</ref> In the US, studies and mitigation only followed decades of health effects on uranium miners of the [[Southwestern United States|Southwestern US]] employed during the early [[Cold War]]; standards were not implemented until 1971.<ref>{{Cite book|last1=Edelstein |first1=Michael R. |last2=William J. |first2=Makofske 
|title=Radon's deadly daughters: science, environmental policy, and the politics of risk |publisher=Rowman & Littlefield |date=1998 |pages= 36–39 |isbn=0-8476-8334-6}}</ref>

In the early 20th century in the US, gold contaminated with the radon daughter <sup>210</sup>Pb entered the jewelry industry. This was from gold [[brachytherapy]] seeds that had held <sup>222</sup>Rn, which were melted down after the radon had decayed.<ref>{{Unbulleted list citebundle|{{cite web |title=Poster Issued by the New York Department of Health (ca. 1981) |publisher=Oak Ridge Associated Universities |date=2021-10-11 |url=https://www.orau.org/health-physics-museum/collection/health-physics-posters/other/poster-issued-by-the-new-york-department-of-health.html |access-date=2021-10-11}}|{{cite news |url=http://www.time.com/time/magazine/article/0,9171,838695,00.html |title=Rings and Cancer |access-date=2009-05-05 |magazine=Time |date=1968-09-13 |archive-date=2009-05-22 |archive-url=https://web.archive.org/web/20090522105043/http://www.time.com/time/magazine/article/0,9171,838695,00.html |url-status=dead }}}}</ref>

The presence of radon in indoor air was documented as early as 1950. Beginning in the 1970s, research was initiated to address sources of indoor radon, determinants of concentration, health effects, and mitigation approaches. In the US, the problem of indoor radon received widespread publicity and intensified investigation after a widely publicized incident in 1984. During routine monitoring at a Pennsylvania nuclear power plant, a worker was found to be contaminated with radioactivity. A high concentration of radon in his home was subsequently identified as responsible.<ref>{{cite journal |last=Samet |first=J. M. |pmc=1003141 |pmid=1734594 |date=1992 |title=Indoor radon and lung cancer. Estimating the risks |volume=156 |issue=1 |pages=25–9 |journal=[[The Western Journal of Medicine]]}}</ref><ref name="George-2008" />