View source for Radium

{{good article}}
{{about|the chemical element}}
{{distinguish|Radon}}
{{pp|small=yes}}
{{Use dmy dates|date=April 2014}}
{{infobox radium}}
[[File:Radium 226 radiation source 1.jpg|270 px|thumb|{{ubl|Radium-226 radiation source.|Activity 3300 Bq (3.3 kBq)}}]]
'''Radium''' is a [[chemical element]]; it has [[chemical symbol|symbol]] '''Ra''' and [[atomic number]] 88. It is the sixth element in [[alkaline earth metal|group&nbsp;2]] of the [[periodic table]], also known as the [[alkaline earth metal]]s. Pure radium is silvery-white, but it readily reacts with nitrogen (rather than oxygen) upon exposure to air, forming a black surface layer of [[radium nitride]] (Ra<sub>3</sub>N<sub>2</sub>). All [[isotopes]] of radium are [[radioactive]], the most stable isotope being [[radium-226]] with a [[half-life]] of 1,600&nbsp;years. When radium decays, it emits [[ionizing radiation]] as a by-product, which can excite [[fluorescent]] chemicals and cause [[radioluminescence]]. For this property, it was widely used in [[Self-luminous paint|self-luminous paints]] following its discovery. Of the [[Radionuclide|radioactive elements]] that occur in quantity, radium is considered particularly [[Toxicity|toxic]], and it is [[Carcinogen|carcinogenic]] due to the radioactivity of both it and its immediate decay product [[radon]] as well as its tendency to [[Bone seeker|accumulate in the bones]].

Radium, in the form of [[radium chloride]], was [[discovery of the chemical elements|discovered]] by [[Marie Curie|Marie]] and [[Pierre Curie]] in 1898 from ore mined at [[Jáchymov]]. They extracted the radium compound from [[uraninite]] and published the discovery at the [[French Academy of Sciences]] five days later. Radium was isolated in its [[metal]]lic state by Marie Curie and [[André-Louis Debierne]] through the [[electrolysis]] of radium chloride in 1910, and soon afterwards the metal started being produced on larger scales in [[Austria]], the [[United States]], and [[Belgium]]. However, the amount of radium produced globally has always been small in comparison to other elements, and by the 2010s, annual production of radium, mainly via extraction from [[spent nuclear fuel]], was less than 100 grams.

In nature, radium is found in [[uranium]] ores in quantities as small as a seventh of a gram per ton of uraninite, and in [[thorium]] ores in trace amounts. Radium is not necessary for [[Biological roles of the elements|living organisms]], and its radioactivity and chemical reactivity make adverse health effects likely when it is incorporated into biochemical processes because of its chemical mimicry of [[calcium]]. As of 2018, other than in [[nuclear medicine]], radium has no commercial applications. Formerly, from the 1910s to the 1970s, it was used as a radioactive source for [[radioluminescent]] devices and also in [[radioactive quackery]] for its supposed curative power. In nearly all of its applications, radium has been replaced with less dangerous [[radioisotopes]], with one of its few remaining non-medical uses being the production of [[actinium]] in [[Nuclear reactor|nuclear reactors]]. 

==Bulk properties==
Radium is the heaviest known [[alkaline earth metal]] and is the only [[radioactive]] member of its group. Its physical and chemical properties most closely resemble its lighter [[congener (chemistry)|congener]], [[barium]].{{sfn|Greenwood|Earnshaw|1997|page=112}}

Pure radium is a [[volatility (chemistry)|volatile]], [[Lustre (mineralogy)|lustrous]] silvery-white metal, even though its lighter congeners [[calcium]], [[strontium]], and barium have a slight yellow tint.{{sfn|Greenwood|Earnshaw|1997|page=112}} Radium's lustrous surface rapidly becomes black upon exposure to air, likely due to the formation of [[radium nitride]] (Ra<sub>3</sub>N<sub>2</sub>).{{sfn|Kirby|Salutsky|1964|page=4}} Its [[melting point]] is either {{convert|700|°C}} or {{convert|960|°C}}{{efn|
Both values are encountered in sources and there is no agreement among scientists as to the true value of the melting point of radium.{{sfn|Kirby|Salutsky|1964|page=4}}
}} and its [[boiling point]] is {{convert|1737|°C}}; however, this is not well established.<ref name="brit">
{{Britannica|489270|Radium|Timothy P. Hanusa}}
</ref> Both of these values are slightly lower than those of barium, confirming [[periodic trend]]s down the group&nbsp;2 elements.<ref name=Lide2004>{{cite book
 |editor1-last = Lide |editor1-first=D.R.
 |display-editors = etal
 |year = 2004
 |title = CRC Handbook of Chemistry and Physics |edition = 84th
 |url = https://archive.org/details/crchandbookofche81lide
 |url-access = registration
 |location = Boca Raton, FL
 |publisher = CRC Press
 |isbn = 978-0-8493-0484-2
}}
</ref>
Like barium and the [[alkali metal]]s, radium crystallizes in the [[body-centered cubic]] structure at [[standard temperature and pressure]]: the radium–radium bond distance is 514.8&nbsp;[[picometer]]s.<ref>{{cite journal
 | last1 = Weigel | first1 = F.
 | last2 = Trinkl | first2 = A.
 | year = 1968
 | title = Zur Kristallchemie des Radiums | language = de
 | trans-title = On radium's chemical chrystalography
 | journal = Radiochim. Acta
 | volume = 10 | issue = 1–2 | page = 78
 | s2cid = 100313675 | doi = 10.1524/ract.1968.10.12.78
}}
</ref>
Radium has a density of 5.5&nbsp;g/cm{{sup|3}}, higher than that of barium, and the two elements have similar [[Crystal structure|crystal structures]] ([[Cubic crystal system|bcc]] at standard temperature and pressure).<ref name="Young">{{cite book |author=Young, David A. |title=Phase Diagrams of the Elements |publisher=University of California Press |year=1991 |isbn=978-0-520-91148-2 |page=85 |chapter=Radium |chapter-url=https://books.google.com/books?id=F2HVYh6wLBcC&pg=PA85}}
</ref><ref>{{cite web
 |title=Crystal structures of the chemical elements at 1&nbsp;bar
 |website=uni-bielefeld.de
 |url=http://wwwhomes.uni-bielefeld.de/achim/ele_structures.html
 |archive-url=https://web.archive.org/web/20140826161012/http://wwwhomes.uni-bielefeld.de/achim/ele_structures.html
 |archive-date=26 August 2014
}}
</ref><!-- books.google.com/books?id=QsgmAAAAMAAJ&q="melting+point+of+radium"&dq="melting+point+of+radium"&hl=de&sa=X&ei=8j_iT72ZAYfOsgb-r91v&ved=0CD4Q6AEwAg books.google.com/books?id=1hNSAAAAMAAJ&q="melting+point+of+radium"&dq="melting+point+of+radium"&hl=de&sa=X&ei=8j_iT72ZAYfOsgb-r91v&ved=0CEgQ6AEwBA -->

==Isotopes==
{{main|Isotopes of radium}}
[[File:Decay chain(4n+2, Uranium series).svg|thumb|upright=1.25|left|[[Decay chain]] of {{sup|238}}U, the primordial [[progenitor]] of {{sup|226}}Ra]]
Radium has 33&nbsp;known isotopes with [[mass number]]s from 202 to 234, all of which are [[radioactive]].{{NUBASE2020|ref}} Four of these – [[radium-223|{{sup|223}}Ra]] ([[half-life]] 11.4&nbsp;days), {{sup|224}}Ra (3.64&nbsp;days), {{sup|226}}Ra (1600&nbsp;years), and {{sup|228}}Ra (5.75&nbsp;years) – occur naturally in the [[decay chain]]s of primordial [[thorium-232]], [[uranium-235]], and [[uranium-238]] ({{sup|223}}Ra from uranium-235, {{sup|226}}Ra from uranium-238, and the other two from thorium-232). These isotopes nevertheless still have [[half-lives]] too short to be [[primordial nuclide|primordial radionuclides]], and only exist in nature from these decay chains.{{sfn|Kirby|Salutsky|1964|page=3}}
Together with the mostly [[synthetic radioisotope|artificial]] {{sup|225}}Ra (15&nbsp;d), which occurs in nature only as a decay product of minute traces of [[neptunium-237]],<ref name="4n1">
{{cite journal
 |last1=Peppard |first1=D.F.     |last2=Mason |first2=G.W.
 |last3=Gray    |first3=P.R.     |last4=Mech  |first4=J.F
 |year=1952
 |title=Occurrence of the (4{{mvar|n}} + 1) series in nature
 |journal=[[Journal of the American Chemical Society]]
 |volume=74 |issue=23 |pages=6081–6084
 |doi=10.1021/ja01143a074
 |bibcode=1952JAChS..74.6081P |url=https://digital.library.unt.edu/ark:/67531/metadc172698/
 |access-date=6 July 2019  |url-status=live 
 |archive-url=https://web.archive.org/web/20190728065436/https://digital.library.unt.edu/ark:/67531/metadc172698/
 |archive-date=28 July 2019
}}
</ref>
these are the five most stable isotopes of radium.{{NUBASE2020|ref}} All other 27&nbsp;known radium isotopes have half-lives under two hours, and the majority have half-lives under a minute.{{NUBASE2020|ref}} Of these, {{sup|221}}Ra (half-life 28&nbsp;s) also occurs as a {{sup|237}}Np daughter, and {{sup|220}}Ra and {{sup|222}}Ra would be produced by the still-unobserved [[double beta decay]] of natural [[Isotopes of radon | radon isotopes]].<ref name="Tretyak2002">{{Cite journal
 |last1=Tretyak |first1=V.I. 
 |last2=Zdesenko |first2=Yu.G. 
 |year=2002
 |title=Tables of Double Beta Decay Data — An Update
 |journal=[[At. Data Nucl. Data Tables]] |volume=80 |issue=1 |pages=83–116
 |doi=10.1006/adnd.2001.0873
|bibcode=2002ADNDT..80...83T }}</ref> At least 12&nbsp;[[nuclear isomer]]s have been reported, the most stable of which is radium-205m with a half-life between 130~230&nbsp;milliseconds; this is still shorter than twenty-four [[ground state|ground-state]] radium isotopes.{{NUBASE2020|ref}}

{{sup|226}}Ra is the most stable isotope of radium and is the last isotope in the {{nobr|(4{{mvar|n}} + 2)}} decay chain of uranium-238 with a half-life of over a millennium; it makes up almost all of natural radium. Its immediate decay product is the dense radioactive [[noble gas]] [[radon]] (specifically the isotope [[radon-222|{{sup|222}}Rn]]), which is responsible for much of the danger of environmental radium.<ref name=epa/>{{efn | See [[radon mitigation]].}} It is 2.7&nbsp;million times more radioactive than the same [[amount of substance|molar amount]] of natural [[uranium]] (mostly uranium-238), due to its proportionally shorter half-life.<ref>
{{cite book
 | last = Soddy  | first = Frederick
 | date = 25 August 2004
 | title = The Interpretation of Radium
 | isbn = 978-0-486-43877-1
 | page = 139&nbsp;ff
 | publisher = Courier Corporation
 | url = https://books.google.com/books?id=ojaelt2o7AQC&pg=PA139
 | access-date = 27 June 2015  | url-status = live  | via = Google Books
 | archive-url = https://web.archive.org/web/20150905172755/https://books.google.com/books?id=ojaelt2o7AQC&pg=PA139
 | archive-date = 5 September 2015
}}
</ref><ref>
{{cite book
 | last1 = Malley | first1 = Marjorie C.
 | year = 2011
 | title = Radioactivity
 | publisher = Oxford University Press
 | isbn = 978-0-19-983178-4
 | url = https://archive.org/details/radioactivityhis0000mall
 | url-access = registration  | access-date = 27 June 2015  | via = Internet Archive (archive.org)
 | page = [https://archive.org/details/radioactivityhis0000mall/page/115 115&nbsp;ff]
}}</ref>

A sample of radium metal maintains itself at a higher [[temperature]] than its surroundings because of the radiation it emits. Natural radium (which is mostly {{sup|226}}Ra) emits mostly [[alpha particles]], but other steps in its decay chain (the [[Decay chain#Uranium series|uranium or radium series]]) emit alpha or [[beta particles]], and almost all particle emissions are accompanied by [[gamma rays]].<ref>{{cite book | url = https://books.google.com/books?id=alC0vvE-ZUwC&pg=PA133 | page = 133 | title = The Becquerel Rays and the Properties of Radium | isbn = 978-0-486-43875-7 | last1 = Strutt | first1 = R.J. | date = 7 September 2004 | publisher = Courier Corporation | access-date = 27 June 2015 | archive-url = https://web.archive.org/web/20150905174214/https://books.google.com/books?id=alC0vvE-ZUwC&pg=PA133 | archive-date = 5 September 2015 | url-status = live }}</ref>

Experimental nuclear physics studies have shown that nuclei of several radium isotopes, such as  {{sup|222}}Ra, {{sup|224}}Ra and {{sup|226}}Ra, have reflection-asymmetric ("pear-like") shapes.<ref>{{cite journal|title=Pear-shaped atomic nuclei|last1 = Butler| first1 = P. A.|journal = Proceedings of the Royal Society A|date=2020 | volume = 476| issue = 2239|page=20200202|doi=10.1098/rspa.2020.0202 |pmid=32821242 |bibcode=2020RSPSA.47600202B |pmc=7426035}}.</ref> In particular, this experimental information on radium-224
has been obtained at [[ISOLDE]] using a technique called [[Coulomb excitation]].<ref>{{cite web|url=https://home.cern/about/updates/2013/05/first-observations-short-lived-pear-shaped-atomic-nuclei|title=First observations of short-lived pear-shaped atomic nuclei – CERN|website=home.cern|access-date=8 June 2018|archive-url=https://web.archive.org/web/20180612145136/https://home.cern/about/updates/2013/05/first-observations-short-lived-pear-shaped-atomic-nuclei|archive-date=12 June 2018|url-status=live}}</ref><ref name=":0">{{cite journal| title = Studies of pear-shaped nuclei using accelerated radioactive beams| year = 2013| last1 = Gaffney| first1 = L. P.| last2 = Butler| first2 = P. A.| last3 = Scheck| first3 = M.| display-authors = etal | journal = Nature| volume = 497| issue = 7448| pages = 199–204| doi = 10.1038/nature12073| pmid = 23657348| bibcode = 2013Natur.497..199G| s2cid = 4380776| url = https://lirias.kuleuven.be/handle/123456789/400663}}</ref>

==Chemistry==
Radium only exhibits the oxidation state of +2 in solution.{{sfn|Kirby|Salutsky|1964|page=4}} It forms the colorless Ra{{sup|2+}} [[cation]] in [[aqueous solution]], which is highly [[base (chemistry)|basic]] and does not form [[coordination complex|complexes]] readily.{{sfn|Kirby|Salutsky|1964|page=4}} Most radium compounds are therefore simple [[ionic bond|ionic]] compounds,{{sfn|Kirby|Salutsky|1964|page=4}} though participation from the [[Electron configuration|6s and 6p electrons]] (in addition to the valence 7s electrons) is expected due to [[relativistic quantum chemistry|relativistic effects]] and would enhance the [[covalent bond|covalent]] character of radium compounds such as [[Radium fluoride|RaF{{sub|2}}]] and Ra[[astatine|At]]{{sub|2}}.<ref name=Thayer>{{cite book |last1=Thayer |first1=John S. |chapter=Relativistic Effects and the Chemistry of the Heavier Main Group Elements |title=Relativistic Methods for Chemists |volume=10 |year=2010 |page=81 |doi=10.1007/978-1-4020-9975-5_2 |isbn=978-1-4020-9974-8 |series=Challenges and Advances in Computational Chemistry and Physics |publisher=Springer |location=Dordrecht }}</ref> For this reason, the [[standard electrode potential]] for the [[half-reaction]] Ra{{sup|2+}} (aq) + 2e{{sup|-}} → Ra (s) is −2.916&nbsp;[[volt|V]], even slightly lower than the value −2.92&nbsp;V for barium, whereas the values had previously smoothly increased down the group (Ca: −2.84&nbsp;V; Sr: −2.89&nbsp;V; Ba: −2.92&nbsp;V).{{sfn|Greenwood|Earnshaw|1997|page=111}} The values for barium and radium are almost exactly the same as those of the heavier alkali metals [[potassium]], [[rubidium]], and [[caesium]].{{sfn|Greenwood|Earnshaw|1997|page=111}}

===Compounds===
Solid radium compounds are white as radium ions provide no specific coloring, but they gradually turn yellow and then dark over time due to self-[[radiolysis]] from radium's [[alpha decay]].{{sfn|Kirby|Salutsky|1964|page=4}} Insoluble radium compounds [[Coprecipitation|coprecipitate]] with all barium, most [[strontium]], and most [[lead]] compounds.{{sfn|Kirby|Salutsky|1964|page=8}}

[[Radium oxide]] (RaO) is poorly characterized, as the reaction of radium with air results in the formation of [[radium nitride]].<ref>{{Cite book |last=Tyler |first=Paul McIntosh |url=https://books.google.com/books?id=1KSfyGTUXpcC&pg=PA2 |title=Radium |date=1930 |publisher=U.S. Department of Commerce, Bureau of Mines |language=en}}</ref> [[Radium hydroxide]] (Ra(OH)<sub>2</sub>) is formed via the reaction of radium metal with water, and is the most readily soluble among the alkaline earth hydroxides and a stronger base than its barium congener, [[barium hydroxide]].{{sfn|Kirby|Salutsky|1964|pages=4-8}} It is also more soluble than [[actinium hydroxide]] and [[thorium hydroxide]]: these three adjacent hydroxides may be separated by precipitating them with [[ammonia]].{{sfn|Kirby|Salutsky|1964|pages=4-8}}

[[Radium chloride]] (RaCl<sub>2</sub>) is a colorless, [[Luminescence|luminescent]] compound. It becomes yellow after some time due to self-damage by the [[alpha radiation]] given off by radium when it decays. Small amounts of barium impurities give the compound a [[Rose (color)|rose color]].{{sfn|Kirby|Salutsky|1964|pages=4-8}} Its  It is soluble in water, though less so than [[barium chloride]], and its solubility decreases with increasing concentration of [[hydrochloric acid]]. Crystallization from aqueous solution gives the dihydrate RaCl<sub>2</sub>·2H<sub>2</sub>O, [[Isomorphism (crystallography)|isomorphous]] with its barium analog.{{sfn|Kirby|Salutsky|1964|pages=4-8}}

[[Radium bromide]] (RaBr<sub>2</sub>) is also a colorless, luminous compound.{{sfn|Kirby|Salutsky|1964|pages=4-8}} In water, it is more soluble than radium chloride. Like radium chloride, crystallization from aqueous solution gives the dihydrate RaBr<sub>2</sub>·2H<sub>2</sub>O, isomorphous with its barium analog. The ionizing radiation emitted by radium bromide excites [[nitrogen]] molecules in the air, making it glow. The [[alpha particle]]s emitted by radium quickly gain two electrons to become neutral [[helium]], which builds up inside and weakens radium bromide crystals. This effect sometimes causes the crystals to break or even explode.{{sfn|Kirby|Salutsky|1964|pages=4-8}}

[[Radium nitrate]] (Ra(NO<sub>3</sub>)<sub>2</sub>) is a white compound that can be made by dissolving [[radium carbonate]] in [[nitric acid]]. As the concentration of nitric acid increases, the solubility of radium nitrate decreases, an important property for the chemical purification of radium.{{sfn|Kirby|Salutsky|1964|pages=4-8}}

Radium forms much the same insoluble salts as its lighter congener barium: it forms the insoluble [[radium sulfate|sulfate]] (RaSO<sub>4</sub>, the most insoluble known sulfate), [[radium chromate|chromate]] (RaCrO<sub>4</sub>), [[radium carbonate|carbonate]] (RaCO<sub>3</sub>), [[radium iodate|iodate]] (Ra(IO<sub>3</sub>)<sub>2</sub>), [[radium tetrafluoroberyllate|tetrafluoroberyllate]] (RaBeF<sub>4</sub>), and nitrate (Ra(NO<sub>3</sub>)<sub>2</sub>). With the exception of the carbonate, all of these are less soluble in water than the corresponding barium salts, but they are all [[isostructural]] to their barium counterparts. Additionally, [[radium phosphate]], [[radium oxalate|oxalate]], and [[radium sulfite|sulfite]] are probably also insoluble, as they [[coprecipitation|coprecipitate]] with the corresponding insoluble barium salts.{{sfn|Kirby|Salutsky|1964|pages=8-9}} The great insolubility of radium sulfate (at 20&nbsp;°C, only 2.1&nbsp;[[milligram|mg]] will dissolve in 1&nbsp;[[kilogram|kg]] of water) means that it is one of the less biologically dangerous radium compounds.{{sfn|Kirby|Salutsky|1964|page=12}} The large ionic radius of Ra{{sup|2+}} (148&nbsp;pm) results in weak ability to form [[Coordination complex|coordination complexes]] and poor extraction of radium from aqueous solutions when not at high pH.{{sfn|Keller|Wolf|Shani|2011|pages=97–98}}

==Occurrence==
All isotopes of radium have half-lives much shorter than the [[age of the Earth]], so that any primordial radium would have decayed long ago. Radium nevertheless still occurs [[Radium and radon in the environment|in the environment]], as the isotopes {{sup|223}}Ra, {{sup|224}}Ra, {{sup|226}}Ra, and {{sup|228}}Ra are part of the decay chains of natural thorium and uranium isotopes; since thorium and uranium have very long half-lives,{{NUBASE2020|ref}} these [[decay product|daughters]] are continually being regenerated by their decay.{{sfn|Kirby|Salutsky|1964|page=3}} Of these four isotopes, the longest-lived is {{sup|226}}Ra (half-life 1600&nbsp;years), a decay product of natural uranium. Because of its relative longevity, {{sup|226}}Ra is the most common isotope of the element, making up about one [[parts per trillion|part per trillion]] of the Earth's crust; essentially all natural radium is {{sup|226}}Ra.{{sfn|Greenwood|Earnshaw|1997|pages=109-110}} Thus, radium is found in tiny quantities in the uranium ore [[uraninite]] and various other uranium [[minerals]], and in even tinier quantities in thorium minerals. One [[ton]] of [[uraninite|pitchblende]] typically yields about one seventh of a [[gram]] of radium.<ref>[http://periodic.lanl.gov/88.shtml "Radium"] {{Webarchive|url=https://web.archive.org/web/20121115182006/http://periodic.lanl.gov/88.shtml |date=15 November 2012 }}, Los Alamos National Laboratory. Retrieved 5 August 2009.</ref> One kilogram of the [[Earth's crust]] contains about 900&nbsp;[[picogram]]s of radium, and one [[liter]] of [[sea water]] contains about 89&nbsp;[[femtogram]]s of radium.<ref name="Raabundance">Section 14, Geophysics, Astronomy, and Acoustics; Abundance of Elements in the Earth's Crust and in the Sea, in Lide, David R. (ed.), ''[[CRC Handbook of Chemistry and Physics]], 85th Edition''. CRC Press. Boca Raton, Florida (2005).</ref>

==History==
{{Further|Marie Curie#New elements}}
[[File:Curie and radium by Castaigne.jpg|thumb|Marie and Pierre Curie experimenting with radium, a drawing by [[André Castaigne]]]]
[[File:US radium standard 1927.jpg|thumb|Glass tube of radium chloride kept by the US Bureau of Standards that served as the primary standard of radioactivity for the United States in 1927.]]
Radium was [[discovery of the chemical elements|discovered]] by [[Marie Curie|Marie Skłodowska-Curie]] and her husband [[Pierre Curie]] on 21 December 1898 in a [[uraninite]] (pitchblende) sample from [[Jáchymov]].<ref name="crc">Hammond, C. R. "Radium" in {{RubberBible92nd}}</ref> While studying the mineral earlier, the Curies removed uranium from it and found that the remaining material was still radioactive. In July 1898, while studying pitchblende, they isolated an element similar to [[bismuth]] which turned out to be [[polonium]]. They then isolated a radioactive mixture consisting of two components: compounds of [[barium]], which gave a brilliant green flame color, and unknown radioactive compounds which gave [[carmine (color)|carmine]] [[spectral line]]s that had never been documented before. The Curies found the radioactive compounds to be very similar to the barium compounds, except they were less soluble. This discovery made it possible for the Curies to isolate the radioactive compounds and discover a new element in them. The Curies announced their discovery to the [[French Academy of Sciences]] on 26 December 1898.<ref>{{multiref2|{{cite journal |year=1898 |title=Sur une nouvelle substance fortement radio-active, contenue dans la pechblende |trans-title=On a new, strongly radioactive substance contained in pitchblende |journal=Comptes Rendus |volume=127 |pages=1215–1217 |url=http://www.aip.org/history/curie/discover.htm |access-date=1 August 2009 |author=Curie, Pierre |author2=Curie, Marie |author3=Bémont, Gustave |name-list-style=amp |archive-url=https://web.archive.org/web/20090806083923/http://www.aip.org/history/curie/discover.htm |archive-date=6 August 2009 |url-status=live }}|{{cite journal | doi = 10.1021/ed010p79 | title = The discovery of the elements. XIX. The radioactive elements |year = 1933 | last1 = Weeks | first1 = Mary Elvira |author-link1=Mary Elvira Weeks| journal = Journal of Chemical Education | volume = 10 | issue = 2 | page = 79|bibcode = 1933JChEd..10...79W }}}}</ref> The naming of radium dates to about 1899, from the French word ''radium'', formed in Modern Latin from ''radius'' (''ray''): this was in recognition of radium's emission of energy in the form of rays.<ref>{{multiref2|{{cite journal|author=Ball, David W. |year=1985 |journal=Journal of Chemical Education |volume=62 |issue=9 |pages=787–788 |title=Elemental etymology: What's in a name? |doi=10.1021/ed062p787 |bibcode=1985JChEd..62..787B}}|{{cite book |last=Carvalho |first=Fernando P. |chapter=Marie Curie and the Discovery of Radium |year=2011 |title=The New Uranium Mining Boom |pages=3–13 |doi=10.1007/978-3-642-22122-4_1 |isbn=978-3-642-22121-7 |series=Springer Geology|publisher=Springer |location=Berlin, Heidelberg }}|{{cite journal |last=Weeks |first=Mary Elvira |year=1933 |title=The discovery of the elements. XIX. The radioactive elements |journal=Journal of Chemical Education |volume=10 |issue=2 |page=79 |doi=10.1021/ed010p79 |bibcode=1933JChEd..10...79W}}}}</ref> The gaseous emissions of radium, radon, were recognized and studied extensively by [[Friedrich Ernst Dorn]] in the early 1900s, though at the time they were characterized as "radium emanations".<ref>{{cite book
 |author=Stwertka, Albert
 |year=1998
 |title=A Guide to the Elements |edition=revised 
 |publisher=Oxford University Press
 |isbn=978-0-19-508083-4
 |page=194
}}</ref>

In September 1910, Marie Curie and [[André-Louis Debierne]] announced that they had isolated radium as a pure [[metal]] through the [[electrolysis]] of pure radium [[chloride]] (RaCl<sub>2</sub>) solution using a [[mercury (element)|mercury]] [[cathode]], producing radium–mercury [[amalgam (chemistry)|amalgam]].<ref name=ColbyChurchill1911>{{cite book |author1=Frank Moore Colby|author2=Allen Leon Churchill|title=New International Yearbook: A Compendium of the World's Progress|url=https://archive.org/details/bub_gb_KWEMAAAAYAAJ |year=1911 |publisher=Dodd, Mead and Co. |page=[https://archive.org/details/bub_gb_KWEMAAAAYAAJ/page/n176 152&nbsp;ff]}}</ref> This amalgam was then heated in an atmosphere of [[hydrogen]] gas to remove the mercury, leaving pure radium metal.<ref>
{{cite journal
 |author1=Curie, Marie
 |author2=Debierne, André
 |name-list-style=amp
 |year=1910
 |title=Sur le radium métallique |language=fr
 |trans-title=On metallic radium
 |journal=Comptes Rendus
 |volume=151 |pages=523–525
 |url=http://visualiseur.bnf.fr/CadresFenetre?O=NUMM-3104&I=523&M=tdm
 |access-date=1 August 2009  |url-status=live
 |archive-url=https://web.archive.org/web/20110720205637/http://visualiseur.bnf.fr/CadresFenetre?O=NUMM-3104&I=523&M=tdm
 |archive-date=20 July 2011
}}
</ref>
Later that same year, E. Ebler isolated radium metal by [[thermal decomposition]] of its [[azide]], Ra(N<sub>3</sub>)<sub>2</sub>.<ref>{{Cite book |last=Mellor |first=J. W. |url=https://library.sciencemadness.org/library/books/Mellor_ACTITC_04.pdf |title=A Comprehensive Treatise on Inorganic and Theoretical Chemistry |date=1929 |publisher=Longmans, Green and Co. Ltd. |page=64}}</ref><ref>{{Cite book |last1=Fair |first1=H. D. |title=Energetic Materials |last2=Walker |first2=R. F. |publisher=Springer |year=1977 |isbn=978-1-4899-5009-3 |location=New York, NY |pages=41–42}}</ref> Radium metal was first industrially produced at the beginning of the 20th century by [[Biraco]], a subsidiary company of [[Union Minière du Haut Katanga]] (UMHK) in its [[Olen, Belgium|Olen]] plant in Belgium.<ref>{{cite book | page = 206 | url = https://books.google.com/books?id=yCkJgKwyAVoC&pg=PA206 | title = Biotechnology for waste management and site restoration: Technological, educational, business, political aspects | isbn = 978-0-7923-4769-9 | author1 = Ronneau, C. | author2 = Bitchaeva, O. | publisher = Scientific Affairs Division, North Atlantic Treaty Organization | date = 1997 | access-date = 27 June 2015 | archive-url = https://web.archive.org/web/20150905180624/https://books.google.com/books?id=yCkJgKwyAVoC&pg=PA206 | archive-date = 5 September 2015 | url-status = live }}</ref> The metal became an important export of Belgium from 1922 up until World War II.<ref>{{Cite journal |last=Adams |first=A |date=January 1993 |title=The origin and early development of the Belgian radium industry |url=https://linkinghub.elsevier.com/retrieve/pii/016041209390274L |journal=Environment International |volume=19 |issue=5 |pages=491–501 |doi=10.1016/0160-4120(93)90274-l |bibcode=1993EnInt..19..491A |issn=0160-4120}}</ref>

The general historical unit for radioactivity, the [[Curie (unit)|curie]], is based on the radioactivity of {{sup|226}}Ra. it was originally defined as the radioactivity of one gram of radium-226,<ref>
{{cite periodical
 | author = Frame, Paul W.
 | date = October–November 1996
 | title = How the Curie came to be
 | periodical = Health Physics Society Newsletter
 | via=[[Oak Ridge Associated Universities]] (orau.org)
 | url = http://www.orau.org/ptp/articlesstories/thecurie.htm
 | access-date = 9 May 2023 <!-- last live 30 April 2008 --> | url-status = usurped
 | archive-url = https://web.archive.org/web/20120320124750/http://www.orau.org/ptp/articlesstories/thecurie.htm
 | archive-date = 20 March 2012
}}
</ref> but the definition was later refined to be {{val|3.7|e=10|u=disintegrations per second}}.<ref>{{Cite book |last=National Research Council (US) Committee on Evaluation of EPA Guidelines for Exposure to Naturally Occurring Radioactive Materials |url=https://www.ncbi.nlm.nih.gov/books/NBK230653/ |title=Evaluation of Guidelines for Exposures to Technologically Enhanced Naturally Occurring Radioactive Materials |publisher=National Academies Press (US) |year=1999 |location=Washington (DC) |chapter=Appendix, Radiation Quantities and Units, Definitions, Acronyms}}</ref>

===Historical applications===
====Luminescent paint====
[[File:Radium 2.jpg|thumb|Watch hands coated with radium paint under ultraviolet light]]
Radium was formerly used in [[luminescence|self-luminous]] paints for watches, aircraft switches, clocks, and instrument dials and panels. A typical self-luminous watch that uses radium paint contains around 1 microgram of radium.<ref name=renamed_from_2024184_on_20240813160145/> In the mid-1920s, a lawsuit was filed against the [[United States Radium Corporation]] by five dying "[[Radium Girls]]" – dial painters who had painted radium-based [[luminous paint]] on the components of watches and clocks.<ref name=":2" /> The dial painters were instructed to lick their brushes to give them a fine point, thereby ingesting radium.<ref name=OakRidge>
{{cite web
 | author = Frame, Paul
 | year = 1999
 | title = Radioluminescent paint
 | website = Museum of Radiation and Radioactivity
 | publisher = [[Oak Ridge Associated Universities]]
 | url = https://www.orau.org/health-physics-museum/collection/radioluminescent/index.html#section-heading-main
 | archive-date = July 31, 2014
 | archive-url = https://web.archive.org/web/20140731220027/http://www.orau.org/ptp/collection/radioluminescent/radioluminescentinfo.htm
 | url-status = live
}}
</ref> Their exposure to radium caused serious health effects which included sores, [[anemia]], and [[bone cancer]].<ref name=epa/>

During the litigation, it was determined that the company's scientists and management had taken considerable precautions to protect themselves from the effects of radiation, but it did not seem to protect their employees. Additionally, for several years the companies had attempted to cover up the effects and avoid liability by insisting that the Radium Girls were instead suffering from [[syphilis]].<ref>{{cite web|url=http://environmentalhistory.org/people/radiumgirls/|title=Environmental history timeline&nbsp;– Radium Girls|access-date=1 Sep 2018|date=2012-07-20|archive-url=https://web.archive.org/web/20180902084212/http://environmentalhistory.org/people/radiumgirls/|archive-date=2 September 2018|url-status=live}}</ref>

As a result of the lawsuit, and an extensive study by the U.S. Public Health Service, the adverse effects of radioactivity became widely known, and radium-dial painters were instructed in proper safety precautions and provided with protective gear. Radium continued to be used in dials, especially in manufacturing during [[World War II]], but from 1925 onward there were no further injuries to dial painters.
<ref name=":2">{{multiref2|Rowland, R. E. (1995) [https://publications.anl.gov/anlpubs/1994/11/16311.pdf Radium in humans: a review of U.S. studies] {{Webarchive|url=https://web.archive.org/web/20111109003623/http://www.osti.gov/accomplishments/documents/fullText/ACC0029.pdf |date=9 November 2011 }}. Argonne National Laboratory. p. 22|{{Cite journal |last=Coursey |first=Bert M. |date=2021 |title=The National Bureau of Standards and the Radium Dial Painters |url=https://nvlpubs.nist.gov/nistpubs/jres/126/jres.126.051.pdf |journal=Journal of Research of the National Institute of Standards and Technology |language=en |volume=126 |doi=10.6028/jres.126.051 |issn=2165-7254 |pmc=10046820 |pmid=38469446}}}}</ref>

From the 1960s the use of radium paint was discontinued. In many cases luminous dials were implemented with non-radioactive fluorescent materials excited by light; such devices glow in the dark after exposure to light, but the glow fades.<ref name="epa" /> Where long-lasting self-luminosity in darkness was required, safer radioactive [[promethium]]-147 (half-life 2.6 years) or [[tritium]] (half-life 12 years) paint was used; both continue to be used as of 2018.<ref>{{multiref2|{{Cite journal |last1=Broderick |first1=Kathleen |last2=Lusk |first2=Rita |last3=Hinderer |first3=James |last4=Griswold |first4=Justin |last5=Boll |first5=Rose |last6=Garland |first6=Marc |last7=Heilbronn |first7=Lawrence |last8=Mirzadeh |first8=Saed |date=February 2019 |title=Reactor production of promethium-147 |url=https://linkinghub.elsevier.com/retrieve/pii/S0969804318305931 |journal=Applied Radiation and Isotopes |language=en |volume=144 |pages=54–63 |doi=10.1016/j.apradiso.2018.10.025|pmid=30529496 |bibcode=2019AppRI.144...54B }}|{{Cite journal |last1=Eyrolle |first1=Frédérique |last2=Ducros |first2=Loïc |last3=Le Dizès |first3=Séverine |last4=Beaugelin-Seiller |first4=Karine |last5=Charmasson |first5=Sabine |last6=Boyer |first6=Patrick |last7=Cossonnet |first7=Catherine |date=January 2018 |title=An updated review on tritium in the environment |url=https://linkinghub.elsevier.com/retrieve/pii/S0265931X17307956 |journal=Journal of Environmental Radioactivity |language=en |volume=181 |pages=128–137 |doi=10.1016/j.jenvrad.2017.11.001|pmid=29149670 |bibcode=2018JEnvR.181..128E }}}}</ref> These had the added advantage of not degrading the phosphor over time, unlike radium.<ref>{{cite book |script-title=ru:Аналитическая химия технеция, прометия, астатина и франция |trans-title=Analytical Chemistry of Technetium, Promethium, Astatine, and Francium |language=ru |first1=Avgusta Konstantinovna |last1=Lavrukhina |first2=Aleksandr Aleksandrovich |last2=Pozdnyakov |date=1966 |publisher=[[Nauka (publisher)|Nauka]] |page=118}}</ref> Tritium as it is used in these applications is considered safer than radium,<ref name="ieer">{{cite web|author=Zerriffi, Hisham|date=January 1996|title=Tritium: The environmental, health, budgetary, and strategic effects of the Department of Energy's decision to produce tritium|url=http://www.ieer.org/reports/tritium.html#(11)|publisher=[[Institute for Energy and Environmental Research]]|access-date=15 September 2010|archive-url=https://web.archive.org/web/20100713051055/http://www.ieer.org/reports/tritium.html#(11)|archive-date=13 July 2010|url-status=live}}</ref> as it emits very low-energy [[beta radiation]]<ref>{{Cite web |title=Physical and Chemical Properties of Tritium |url=https://www.nrc.gov/docs/ML2034/ML20343A210.pdf |access-date=25 October 2024 |website=Nuclear Regulatory Commission}}</ref> (even lower-energy than the beta radiation emitted by promethium)<ref>{{Cite thesis |last=Hinderer |first=James Howard |title=Radioisotopic Impurities in Promethium-147 Produced at the ORNL High Flux Isotope Reactor |date=2010 |degree=Master's |publisher=University of Tennessee |url=https://trace.tennessee.edu/utk_gradthes/717}}</ref> which cannot penetrate the skin,<ref>
{{cite report
 |title=Hydrogen-3
 |series=Nuclide safety data sheet
 |publisher=Environmental Health & Safety Office, [[Emory University]]
 |via=ehso.emory.edu
 |url=http://www.ehso.emory.edu/content-forms/3anuclidedatasafetysheets.pdf   <!-- presumed -->
 |archive-url=https://web.archive.org/web/20130520184942/http://www.ehso.emory.edu/content-forms/3anuclidedatasafetysheets.pdf
 |archive-date=2013-05-20  }}
</ref> unlike the gamma radiation emitted by radium isotopes.<ref name="ieer" />
[[File:WWI German altimeter radium painted.jpg|thumb|left|A zeppelin [[altimeter]] from [[World War I]]. The dial, previously painted with a luminescent radium paint, has turned yellow due to the degradation of the fluorescent [[zinc sulfide]] medium.]]
Clocks, watches, and instruments dating from the first half of the 20th century, often in military applications, may have been painted with radioactive luminous paint. They are usually no longer luminous; this is not due to radioactive decay of the radium (which has a half-life of 1600&nbsp;years) but to the fluorescence of the zinc sulfide fluorescent medium being worn out by the radiation from the radium.{{sfn|Emsley|2003|page=351}} 
Originally appearing as white, most radium paint from before the 1960s has tarnished to yellow over time. The radiation dose from an intact device is usually only a hazard when many devices are grouped together or if the device is disassembled or tampered with.<ref>{{Cite web |last= |first= |date=2024-05-27 |title=Could your collectible item contain radium? |url=https://www.cnsc-ccsn.gc.ca/eng/resources/radiation/could-your-collectible-item-contain-radium/ |access-date=2024-10-22 |website=Canadian Nuclear Safety Commission}}</ref>

==== Use in electron tubes ====
Radium has been used in [[vacuum tube|electron tube]]s, such as the Western Electric 346B tube. These devices contain a small amount of radium (in the form of [[radium bromide]])<ref>{{Cite web|url=https://tubedata.altanatubes.com.br/sheets/084/3/346B.pdf |via=Altana Tubes |title=Electron Tube Data Sheet: Western Electric 346B Electron Tube |publisher=Bell System Practices |date=April 1956 |access-date=February 12, 2025}}</ref> to ionize the fill gas, typically a noble gas like [[neon]] or [[argon]]. This ionization ensures reliable and consistent operation by providing a steady current when a high voltage is applied, enhancing the device's performance and stability. The radium is sealed within a glass envelope with two electrodes, one of which is coated with the radioactive material to create an ion path between the electrodes.<ref>{{Cite web |title=Electron Tubes |url=https://www.orau.org/health-physics-museum/collection/consumer/miscellaneous/electron-tubes.html |access-date=2025-02-12 |website=Museum of Radiation and Radioactivity |language=en}}</ref>

====Quackery====
{{Main|Radioactive quackery|Radium fad}}[[File:Radior_cosmetics_containing_radium_1918.jpg|thumb|1918 ad for Radior, one of several cosmetic products claiming to contain radium for its purported curative properties<ref>{{Cite journal |last1=Díaz Díaz |first1=R.M. |last2=Garrido Gutiérrez |first2=C. |last3=Maldonado Cid |first3=P. |date=December 2020 |title=Radioactive Cosmetics and Radiant Beauty |journal=Actas Dermo-Sifiliográficas (English Edition) |language=en |volume=111 |issue=10 |pages=863–865 |doi=10.1016/j.adengl.2020.09.014|doi-access=free }}</ref>]]

Radium was once an additive in products such as cosmetics, soap, razor blades, and even beverages due to its supposed curative powers. Many contemporary products were falsely advertised as being radioactive.<ref>{{Cite web |last=Prisco |first=Jacopo |date=2020-03-03 |title=When beauty products were radioactive |url=https://www.cnn.com/style/article/when-beauty-products-were-radioactive/index.html |access-date=2024-10-13 |website=CNN |language=en}}</ref> Such products soon fell out of vogue and were prohibited by authorities in many countries after it was discovered they could have serious adverse health effects. (See, for instance, ''[[Radithor]]'' or ''[[Revigator]]'' types of "radium water" or "Standard Radium Solution for Drinking".){{sfn|Emsley|2003|page=351}} [[Destination spa|Spas]] featuring radium-rich water are still occasionally touted as beneficial, such as those in [[Misasa, Tottori]], Japan,<ref>{{Cite journal |last1=Morinaga |first1=H. |last2=Mifune |first2=M. |last3=Furuno |first3=K. |date=1984 |title=Radioactivity of water and air in Misasa Spa, Japan |url=https://inis.iaea.org/search/search.aspx?orig_q=RN:15072187 |journal=Radiation Protection Dosimetry |volume=7 |issue=1–4 |pages=295–297 |doi=10.1093/oxfordjournals.rpd.a083014 |issn=0144-8420 |via=International Nuclear Information System}}</ref> though the sources of radioactivity in these spas vary and may be attributed to [[radon]] and other radioisotopes.<ref>{{multiref2|{{Cite journal |last1=Gulan |first1=Ljiljana |last2=Penjišević |first2=Ivana |last3=Stajic |first3=Jelena M. |last4=Milenkovic |first4=Biljana |last5=Zeremski |first5=Tijana |last6=Stevanović |first6=Vladica |last7=Valjarević |first7=Aleksandar |date=March 2020 |title=Spa environments in central Serbia: Geothermal potential, radioactivity, heavy metals and PAHs |url=https://linkinghub.elsevier.com/retrieve/pii/S0045653519324105 |journal=Chemosphere |language=en |volume=242 |pages=125171 |doi=10.1016/j.chemosphere.2019.125171|pmid=31671300 |bibcode=2020Chmsp.24225171G }}|{{Cite journal |last1=Sainz |first1=Carlos |last2=Rábago |first2=Daniel |last3=Fuente |first3=Ismael |last4=Celaya |first4=Santiago |last5=Quindós |first5=Luis Santiago |date=February 2016 |title=Description of the behavior of an aquifer by using continuous radon monitoring in a thermal spa |url=https://linkinghub.elsevier.com/retrieve/pii/S0048969715310330 |journal=Science of the Total Environment |language=en |volume=543 |issue=Pt A |pages=460–466 |doi=10.1016/j.scitotenv.2015.11.052|pmid=26599146 |bibcode=2016ScTEn.543..460S |hdl=10902/31301 |hdl-access=free }}|{{Cite journal |last1=Uzun |first1=Sefa Kemal |last2=Demiröz |first2=Işık |date=September 2016 |title=Radon and Progeny Sourced Dose Assessment of Spa Employees in Balneological Sites |url=https://academic.oup.com/rpd/article-lookup/doi/10.1093/rpd/ncv413 |journal=Radiation Protection Dosimetry |language=en |volume=170 |issue=1–4 |pages=331–335 |doi=10.1093/rpd/ncv413 |pmid=26424134 |issn=0144-8420}}|{{Cite journal |last1=Walencik-Łata |first1=A. |last2=Kozłowska |first2=B. |last3=Dorda |first3=J. |last4=Przylibski |first4=T.A. |date=November 2016 |title=The detailed analysis of natural radionuclides dissolved in spa waters of the Kłodzko Valley, Sudety Mountains, Poland |url=https://linkinghub.elsevier.com/retrieve/pii/S0048969716313742 |journal=Science of the Total Environment |language=en |volume=569-570 |pages=1174–1189 |doi=10.1016/j.scitotenv.2016.06.192|pmid=27432727 |bibcode=2016ScTEn.569.1174W }}|{{Cite journal |last1=Karakaya |first1=Muazzez Çelik |last2=Doğru |first2=Mahmut |last3=Karakaya |first3=Necati |last4=Kuluöztürk |first4=Fatih |last5=Nalbantçılar |first5=Mahmut Tahir |date=2017-08-01 |title=Radioactivity and hydrochemical properties of certain thermal Turkish spa waters |url=https://iwaponline.com/jwh/article/15/4/591/28582/Radioactivity-and-hydrochemical-properties-of |journal=Journal of Water and Health |language=en |volume=15 |issue=4 |pages=591–601 |doi=10.2166/wh.2017.263 |pmid=28771156 |bibcode=2017JWH....15..591K |issn=1477-8920}}|{{Cite journal |last1=Duran |first1=Selcen Uzun |last2=Kucukomeroglu |first2=Belgin |last3=Damla |first3=Nevzat |last4=Taskin |first4=Halim |last5=Celik |first5=Necati |last6=Cevik |first6=Uğur |last7=Ersoy |first7=Hakan |date=2017-01-02 |title=Radioactivity measurements and risk assessments of spa waters in some areas in Turkey |url=https://www.tandfonline.com/doi/full/10.1080/10256016.2016.1116986 |journal=Isotopes in Environmental and Health Studies |language=en |volume=53 |issue=1 |pages=91–103 |doi=10.1080/10256016.2016.1116986 |pmid=27008087 |bibcode=2017IEHS...53...91D |issn=1025-6016}}}}</ref>

====Medical and research uses====
Radium (usually in the form of [[radium chloride]] or radium bromide) was used in [[medicine]] to produce radon gas, which in turn was used as a [[cancer]] treatment.<ref name=brit/> Several of these radon sources were used in Canada in the 1920s and 1930s.<ref>
{{cite book
 |first = Charles | last = Hayter
 |year = 2005
 |chapter = The politics of radon therapy in the 1930s
 |title = An Element of Hope: Radium and the response to cancer in Canada, 1900–1940
 |publisher = McGill-Queen's Press
 |isbn = 978-0-7735-2869-7
 |chapter-url = https://books.google.com/books?id=NtKUdnjaCxMC&pg=PA135
 |via=Google Books
}}
</ref> However, many treatments that were used in the early 1900s are not used anymore because of the harmful effects radium bromide exposure caused. Some examples of these effects are [[anaemia]], cancer, and [[mutation|genetic mutations]].<ref name=Harvie>{{cite journal | doi = 10.1016/S0160-9327(99)01201-6| pmid = 10589294| title = The radium century| journal = Endeavour| volume = 23| issue = 3| pages = 100–105|year = 1999| last1 = Harvie| first1 = David I.}}</ref> As of 2011, safer gamma emitters such as [[cobalt-60|{{sup|60}}Co]], which is less costly and available in larger quantities, were usually used to replace the historical use of radium in this application,{{sfn|Keller|Wolf|Shani|2011|pages=97–98}} but factors including increasing costs of cobalt and risks of keeping radioactive sources on site have led to an increase in the use of [[linear particle accelerator]]s for the same applications.<ref>{{Cite journal|url=https://amos3.aapm.org/abstracts/pdf/166-58831-15631646-171798-1721147678.pdf |title=A RETROSPECTIVE OF COBALT-60 RADIATION THERAPY: "THE ATOM BOMB THAT SAVES LIVES" |journal=Medical Physics International |last1=Van Dyk |first1=J. |first2=J. J. |last2=Battista |last3=Almond |first3=P. R. |date=2020}}</ref>

In the U.S., from 1940 through the 1960s, radium was used in [[Pharynx|nasopharyngeal]] radium irradiation, a treatment that was administered to children to treat [[hearing loss]] and chronic [[otitis]]. The procedure was also administered to [[Airman|airmen]] and [[submarine]] crew to treat [[barotrauma]].<ref>{{Cite journal |last1=Ronckers |first1=Cécile M |last2=Land |first2=Charles E |last3=Hayes |first3=Richard B |last4=Verduijn |first4=Pieter G |last5=Stovall |first5=Marilyn |last6=van Leeuwen |first6=Flora E |date=December 2002 |title=Late Health Effects of Childhood Nasopharyngeal Radium Irradiation: Nonmelanoma Skin Cancers, Benign Tumors, and Hormonal Disorders |url=https://www.nature.com/doifinder/10.1203/00006450-200212000-00007 |journal=Pediatric Research |volume=52 |issue=6 |pages=850–858 |doi=10.1203/00006450-200212000-00007 |pmid=12438660 |issn=0031-3998}}</ref><ref>{{Cite web |last=CDC |date=2024-02-20 |title=Facts About Nasopharyngeal Radium Irradiation (NRI) |url=https://www.cdc.gov/radiation-health/data-research/facts-stats/nasopharyngeal-radium-irradiation.html |access-date=2024-10-13 |website=Radiation and Your Health |language=en-us}}</ref>

Early in the 1900s, biologists used radium to induce mutations and study [[genetics]]. As early as 1904, Daniel MacDougal used radium in an attempt to determine whether it could provoke sudden large mutations and cause major evolutionary shifts. [[Thomas Hunt Morgan]] used radium to induce changes resulting in white-eyed fruit flies. Nobel-winning biologist [[Hermann Joseph Muller|Hermann Muller]] briefly studied the effects of radium on fruit fly mutations before turning to more affordable x-ray experiments.<ref name="Hamilton">{{cite journal |last1=Hamilton |first1=Vivien |date=2016 |title=The Secrets of Life: Historian Luis Campos resurrects radium's role in early genetics research |url=https://www.sciencehistory.org/distillations/magazine/the-secrets-of-life |url-status=live |journal=Distillations |volume=2 |issue=2 |pages=44–45 |archive-url=https://web.archive.org/web/20180323154857/https://www.sciencehistory.org/distillations/magazine/the-secrets-of-life |archive-date=23 March 2018 |access-date=22 March 2018}}</ref>

==Production==
[[File:Památník objevu radia v Jáchymově.jpg|thumb|Monument to the Discovery of Radium in [[Jáchymov]]]]
Uranium had no large scale application in the late 19th century and therefore no large uranium mines existed. In the beginning, the [[silver]] mines in [[Jáchymov]], [[Austria-Hungary]] (now [[Czech Republic]]) were the only large sources for uranium ore.<ref name="crc" /> The uranium ore was only a [[byproduct]] of the mining activities.<ref name="Ceranski">{{cite journal |last1=Ceranski |first1=Beate |year=2008 |title=Tauschwirtschaft, Reputationsökonomie, Bürokratie |journal=NTM Zeitschrift für Geschichte der Wissenschaften, Technik und Medizin |language=de |volume=16 |issue=4 |pages=413–443 |doi=10.1007/s00048-008-0308-z |doi-access=free}}</ref>

In the first extraction of radium, Curie used the residues after extraction of uranium from pitchblende. The uranium had been extracted by dissolution in [[sulfuric acid]] leaving radium sulfate, which is similar to [[barium sulfate]] but even less soluble in the residues. The residues also contained rather substantial amounts of barium sulfate which thus acted as a carrier for the radium sulfate. The first steps of the radium extraction process involved boiling with sodium hydroxide, followed by [[hydrochloric acid]] treatment to minimize impurities of other compounds. The remaining residue was then treated with [[sodium carbonate]] to convert the barium sulfate into barium carbonate (carrying the radium), thus making it soluble in hydrochloric acid. After dissolution, the barium and radium were reprecipitated as sulfates; this was then repeated to further purify the mixed sulfate. Some impurities that form insoluble sulfides were removed by treating the chloride solution with [[hydrogen sulfide]], followed by filtering. When the mixed sulfates were pure enough, they were once more converted to mixed chlorides; barium and radium thereafter were separated by [[fractional crystallization (chemistry)|fractional crystallisation]] while monitoring the progress using a [[spectroscope]] (radium gives characteristic red lines in contrast to the green barium lines), and the [[electroscope]].<ref>{{Cite book|title=The Becquerel rays and the properties of radium |author=Hon. R. J. Strutt |location=London|publisher=Edward Arnold |date=1904}} {{endash}} via [http://lateralscience.blogspot.se/2012/11/marie-curie-method-of-extraction-of.html "Lateral Science"] {{Webarchive|url=https://web.archive.org/web/20150402105852/http://lateralscience.blogspot.se/2012/11/marie-curie-method-of-extraction-of.html |date=2 April 2015 }}. ''lateralscience.blogspot.se''. November 2012</ref>

After the isolation of radium by Marie and Pierre Curie from uranium ore from [[Jáchymov]], several scientists started to isolate radium in small quantities. Later, small companies purchased mine tailings from Jáchymov mines and started isolating radium. In 1904, the Austrian government [[nationalization|nationalised]] the mines and stopped exporting raw ore. Until 1912, when radium production increased, radium availability was low.<ref name="Ceranski" />

The formation of an Austrian monopoly and the strong urge of other countries to have access to radium led to a worldwide search for uranium ores. The United States took over as leading producer in the early 1910s,<ref name="crc" /> producing 70&nbsp;g total from 1913 to 1920 in [[Pittsburgh]] alone.<ref name=":1" />

The Curies' process was still used for industrial radium extraction in 1940, but mixed bromides were then used for the fractionation. If the barium content of the uranium ore is not high enough, additional barium can be added to carry the radium. These processes were applied to high grade uranium ores but may not have worked well with low grade ores.<ref>{{Cite journal | doi = 10.1021/ed017p417| title = Extraction of radium from Canadian pitchblende| journal = Journal of Chemical Education| volume = 17| issue = 9| page = 417| year = 1940| last1 = Kuebel | first1 = A. | bibcode = 1940JChEd..17..417K}}</ref> Small amounts of radium were still extracted from uranium ore by this method of mixed precipitation and ion exchange as late as the 1990s,{{sfn|Greenwood|Earnshaw|1997|pages=109-110}} but as of 2011, it is extracted only from spent nuclear fuel.{{sfn|Emsley|2003|page=437}} Pure radium metal is isolated by reducing radium oxide with aluminium metal in a vacuum at 1,200&nbsp;°C.{{sfn|Keller|Wolf|Shani|2011|pages=97–98}}

In 1954, the total worldwide supply of purified radium amounted to about {{convert|5|lb|kg}}.<ref name=renamed_from_2024184_on_20240813160145>
{{cite journal
 |last1=Terrill  |first1=J.G. Jr.
 |last2=Ingraham |first2= S.C., 2nd
 |last3=Moeller  |first3=D.W.
 |year=1954
 |title=Radium in the healing arts and in industry: Radiation exposure in the United States
 |journal=Public Health Reports
 |volume=69 |issue=3 |pages=255–262
 |doi=10.2307/4588736 |jstor=4588736
 |pmc=2024184 |pmid=13134440
}}
</ref> [[Zaire]] and Canada were briefly the largest producers of radium in the late 1970s.<ref name=":1">{{Cite book |url=https://www.ncbi.nlm.nih.gov/books/NBK595989/ |title=Toxicological Profile for Radium |publisher=Agency for Toxic Substances and Disease Registry (US) |location=Atlanta (GA) |publication-date=December 4, 1990 |chapter=Production, Import, Use and Disposal}}</ref> As of 1997 the chief radium-producing countries were Belgium, Canada, the Czech Republic, Slovakia, the United Kingdom, and Russia.{{sfn|Greenwood|Earnshaw|1997|pages=109-110}} The annual production of radium compounds was only about 100&nbsp;g in total as of 1984;{{sfn|Greenwood|Earnshaw|1997|pages=109-110}} annual production of radium had reduced to less than 100&nbsp;g by 2018.<ref>{{Cite journal |last=Cantrill |first=Vikki |date=2018-07-20 |title=The realities of radium |url=https://www.nature.com/articles/s41557-018-0114-8 |journal=Nature Chemistry |volume=10 |issue=8 |pages=898 |doi=10.1038/s41557-018-0114-8 |pmid=30030531 |bibcode=2018NatCh..10..898C |issn=1755-4330}}</ref>

==Modern applications==
Radium is seeing increasing use in the field of [[atomic, molecular, and optical physics]].<ref>{{multiref2|{{Cite thesis|url=https://www.proquest.com/docview/2857719184 |last1=Fan |first1=Mingyu |title=Radium Ions and Radioactive Molecules for Probing New Physics |location=University of California, Santa Barbara |date=June 2023|id={{ProQuest|2857719184}} }}|{{Cite web|title=Radioactive molecules at ISOLDE |url=https://cds.cern.ch/record/2748712/files/INTC-I-227.pdf |first1=M. |last1=Athanasakis |first2=S.G. |last2=Wilkins |first3= T.E. |last3=Cocolios |first4=K.T. |last4=Flanagan |first5=R.F. |last5=Garcia Ruiz |first6=G. |last6=Neyens |first7=X.F. |last7=Yang |first8=M. |last8=Au |first9=R. |last9=Berger |first10=M.L. |last10=Bissell |first11=A. |last11=Borschevsky |first12=A.A. |last12=Breier |first13=A. |last13=Brinson |first14=R.P. |last14=de Groote |first15=Ch.E. |last15=Düllmann |first16=K. |last16=Gaul |first17=S. |last17=Geldhof |first18=T.F. |last18=Giesen |first19=F.P. |last19=Gustafsson |first20=J. |last20=Karthein |first21=Á. |last21=Koszorús |first22=S. |last22=Lechner |first23=S. |last23=Malbrunot-Ettenauer |first24=S. |last24=Rothe |first25=S. |last25=Sels |first26=J. |last26=Stohner |first27=S. |last27=Udrescu |first28=P. |last28=Van Duppen |first29=A.R. |last29=Vernon |first30=M. |last30=Vilén |date=6 January 2021 |publisher=[[European Organization for Nuclear Research]]}}}}</ref><ref name=":0" /> [[Symmetry breaking]] forces scale proportional to <math>\ Z^3\ ,</math><ref>{{multiref2|{{Cite journal|title=Parity violation in atoms|first1=Marie-Anne|last1=Bouchiat|first2=Claude|last2=Bouchiat|date=28 November 1997|journal=Reports on Progress in Physics|volume=60|issue=11|pages=1351–1396|via=Institute of Physics|doi=10.1088/0034-4885/60/11/004|bibcode=1997RPPh...60.1351B|s2cid=250910046 }}|{{Cite journal|url=https://aapt.scitation.org/doi/10.1119/1.2710486|title=The electric dipole moment of the electron: An intuitive explanation for the evasion of Schiff's theorem|first1=Eugene D.|last1=Commins|first2=J. D.|last2=Jackson|first3=David P.|last3=DeMille|date=10 May 2007|journal=American Journal of Physics|volume=75|issue=6|pages=532–536|via=aapt.scitation.org (Atypon)|doi=10.1119/1.2710486|bibcode=2007AmJPh..75..532C}}}}</ref> which makes radium, the heaviest alkaline earth element, well suited for constraining new physics beyond the [[Standard Model|standard model]]. Some radium isotopes, such as radium-225, have [[octupole]] deformed parity doublets that enhance sensitivity to [[CP violation|charge parity violating]] new physics by two to three orders of magnitude compared to {{sup|199}}Hg.<ref>{{multiref2|
{{cite journal
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{{cite journal
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{{cite journal
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 |journal=[[Physical Review Letters]]
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</ref>

Radium is also a promising candidate for trapped ion [[Atomic clock#Optical clocks|optical clocks]].  The radium ion has two subhertz-linewidth transitions from the <math>\ \mathrm{ 7s^2S_{1/2} }\ </math> ground state that could serve as the clock transition in an optical clock.<ref>{{Cite journal|title=Ra+ ion trapping: toward an atomic parity violation measurement and an optical clock |first1=M. |last1=Nuñez Portela |first2=E.A. |last2=Dijck |first3=A.|last3=Mohanty |first4=H.|last4=Bekker |first5=J.E. |last5=van den Berg |first6=G.S. |last6=Giri |first7=S. |last7=Hoekstra |first8=C.J.G. |last8=Onderwater |first9=S. |last9=Schlesser |first10=R.G.E. |last10=Timmermans |first11=O.O. |last11=Versolato |first12=L. |last12=Willmann |first13=H.W. |last13=Wilschut |first14=K. |last14=Jungmann |display-authors=6 |date=1 January 2014|journal=Applied Physics B |volume=114 |issue=1 |pages=173–182 |via=Springer Link |doi=10.1007/s00340-013-5603-2 |bibcode=2014ApPhB.114..173N |s2cid=119948902}}</ref> A {{sup|226}}Ra+ trapped ion atomic clock has been demonstrated on the <math>\ \mathrm{ 7s^2S_{1/2} }\ </math> to <math>\ \mathrm{ 6d^2D_{5/2} }\ </math> transition, which has been considered for the creation of a transportable optical clock as all transitions necessary for clock operation can be addressed with direct diode lasers at common wavelengths.<ref>{{cite journal |url=https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.033202 |title=Radium ion optical clock |first1=C.A. |last1=Holliman |first2=M. |last2=Fan |first3=A. |last3=Contractor |first4=S.M. |last4=Brewer |first5=A.M. |last5=Jayich |date=20 January 2022 |journal=Physical Review Letters |volume=128 |issue=3 |page=033202 |via=APS |doi=10.1103/PhysRevLett.128.033202 |pmid=35119894 |arxiv=2201.07330 |bibcode=2022PhRvL.128c3202H |s2cid=246035333 }}</ref>

Some of the few practical uses of radium are derived from its radioactive properties. More recently discovered [[radioisotope]]s, such as [[cobalt-60]] and [[caesium-137]], are replacing radium in even these limited uses because several of these isotopes are more powerful emitters, safer to handle, and available in more concentrated form.<ref>{{multiref2|
{{cite report
 | title = Radiation Source Use and Replacement: Abbreviated version
 | date = January 2008
 | series = Committee on Radiation Source Use and Replacement / Nuclear and Radiation Studies Board 
 | publisher = U.S. National Research Council / National Academies Press
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 | archive-url = https://web.archive.org/web/20150905164805/https://books.google.com/books?id=3cT2REdXJ98C&pg=PA24
 | archive-date = 5 September 2015
}}|{{cite book
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 | year = 1996
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 | archive-date = 5 September 2015
}}}}
</ref>

The isotope [[Radium-223|{{sup|223}}Ra]] was approved by the United States [[Food and Drug Administration]] in 2013 for use in [[medicine]] as a [[cancer]] treatment of bone [[metastasis]] in the form of a solution<ref name="XofigoSPC">{{cite web |date=11 October 2018 |title=Xofigo Summary of Product Characteristics |url=https://www.ema.europa.eu/en/documents/product-information/xofigo-epar-product-information_en.pdf |access-date=9 October 2019 |website=European Medicines Authority |publisher=Bayer}}</ref> including radium-223 chloride.<ref name="FBT-FDA2013">{{multiref2|{{Cite web |title=FDA OKs pinpoint prostate cancer radiation drug Xofigo from Bayer, Algeta |url=http://www.fiercebiotech.com/story/breaking-fda-oks-pinpoint-prostate-cancer-radiation-drug-xofigo-bayer-alget/2013-05-15 |archive-url=https://archive.today/20130628025639/http://www.fiercebiotech.com/story/breaking-fda-oks-pinpoint-prostate-cancer-radiation-drug-xofigo-bayer-alget/2013-05-15 |archive-date=28 June 2013  |access-date=1 October 2014 }}|{{cite news |title=FDA approves Xofigo for advanced prostate cancer |website=cancer.org |date=2013-05-15 |url=http://www.cancer.org/cancer/news/news/fda-approves-xofigo-for-advanced-prostate-cancer  <!-- presumed --> |archive-url=https://web.archive.org/web/20130706233317/http://www.cancer.org/cancer/news/news/fda-approves-xofigo-for-advanced-prostate-cancer |archive-date=2013-07-06}}}}</ref> The main indication of treatment is the therapy of [[Bone metastases|bony metastases]] from castration-resistant prostate cancer.<ref>
{{cite journal
 | last1 = Maffioli | first1 = L.        | last2 = Florimonte | first2 = L.
 | last3 = Costa    | first3 = D.C.      | last4 = Correia Castanheira | first4 = J.
 | last5 = Grana    | first5 = C.        | last6 = Luster     | first6 = M.
 | last7 = Bodei    | first7 = L.        | last8 = Chinol     | first8 = M.
 | display-authors=6
 | year=2015
 | title=New radiopharmaceutical agents for the treatment of castration-resistant prostate cancer
 | journal=Q J Nucl Med Mol Imaging
 | volume=59 | issue=4 | pages=420–438
 | pmid=26222274
 | url = https://www.researchgate.net/publication/280586798
}}
</ref>
{{sup|225}}Ra has also been used in experiments concerning therapeutic irradiation, as it is the only reasonably long-lived radium isotope which does not have radon as one of its daughters.<ref>{{cite book |first=Wolfgang |last=Stoll |chapter=Thorium and Thorium Compounds |doi=10.1002/14356007.a27_001 |title=Ullmann's Encyclopedia of Industrial Chemistry |publisher=[[Wiley-VCH]] |year=2005 |isbn=978-3-527-31097-5 |page=717}}</ref>

Radium was still used in 2007 as a radiation source in some [[industrial radiography]] devices to check for flawed metallic parts, similarly to [[X-ray imaging]].<ref name=epa/> When mixed with [[beryllium]], radium acts as a [[neutron source]].{{sfn|Emsley|2003|page=351}}<ref>{{cite book | chapter-url = https://books.google.com/books?id=YpEiPPFlNAAC&pg=PA261 | pages = 260–261 | chapter = Alpha particle induced nuclear reactions | title = Radioactivity: Introduction and history | isbn = 978-0-444-52715-8 | last1 = l'Annunziata | first1 = Michael F. | date = 2007|publisher=Elsevier}}</ref> Up until at least 2004, radium-beryllium neutron sources were still sometimes used,<ref name=epa>
{{cite report
 |title=Radiation protection
 |department=Radium
 |series=Radiation / Radionuclides
 |publisher=[[United States Environmental Protection Agency]]
 |website=epa.gov
 |url=http://www.epa.gov/radiation/radionuclides/radium.html   <!-- presumed -->
 |archive-url=https://web.archive.org/web/20150211154556/http://www.epa.gov/radiation/radionuclides/radium.html
 |archive-date=2015-02-11 }}
</ref><ref>
{{cite journal
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 | year = 2004
 | title = Radiation dosimetry of a graphite moderated radium-beryllium source
 | journal = Health Physics
 | volume = 86 | issue = 5&nbsp;Supplement | pages = S110–S112
 | bibcode = 2003rdtc.conf..484H  | pmid = 15069300
 | doi = 10.1142/9789812705563_0060
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 | access-date = 25 October 2017  | url-status = live
 | archive-url = https://web.archive.org/web/20180723003837/https://www.bnl.gov/isd/documents/24293.pdf
 | archive-date = 23 July 2018
}}
</ref>
but other materials such as [[polonium]] and [[americium]] have become more common for use in neutron sources. RaBeF<sub>4</sub>-based (α, n) neutron sources have been deprecated despite the high number of neutrons they emit (1.84×10{{sup|6}} neutrons per second) in favour of [[americium-241|{{sup|241}}Am]]–Be sources.{{sfn|Keller|Wolf|Shani|2011|pages=96–98}} {{As of|2011}}, the isotope {{sup|226}}Ra is mainly used to form {{sup|227}}[[actinium|Ac]] by [[neutron irradiation]] in a nuclear reactor.{{sfn|Keller|Wolf|Shani|2011|pages=97–98}}

==Hazards==
Radium is highly radioactive, as is its immediate decay product, [[radon]] gas. When ingested, 80% of the ingested radium leaves the body through the [[feces]], while the other 20% goes into the [[bloodstream]], mostly accumulating in the bones. This is because the body treats radium as [[calcium]] and [[bone seeker|deposits it in the bones]], where radioactivity degrades [[bone marrow|marrow]] and can mutate [[bone cells]]. Exposure to radium, internal or external, can cause cancer and other disorders, because radium and radon emit alpha and [[gamma ray]]s upon their decay, which kill and mutate cells.<ref name=epa/> Radium is generally considered the most toxic of the radioactive elements.{{sfn|Keller|Wolf|Shani|2011|pages=96–98}} <!-- http://www.osti.gov/accomplishments/documents/fullText/ACC0029.pdf -->

Some of the biological effects of radium include the first case of "radium-dermatitis", reported in 1900, two years after the element's discovery. The French physicist [[Antoine Becquerel]] carried a small ampoule of radium in his waistcoat pocket for six hours and reported that his skin became [[Ulcer (dermatology)|ulcerated]]. Pierre Curie attached a tube filled with radium to his arm for ten hours, which resulted in the appearance of a skin lesion, suggesting the use of radium to attack cancerous tissue as it had attacked healthy tissue.<ref>
{{cite book
 |last=Redniss |first=Lauren
 |year=2011
 |title=Radioactive: Marie & Pierre Curie: A tale of love and fallout
 |publisher=HarperCollins
 |location=New York, NY
 |isbn=978-0-06-135132-7
 |page=70
}}
</ref>
Handling of radium has been blamed for Marie Curie's death, due to [[aplastic anemia]],<ref>{{Cite web |title=Aplastic Anemia |url=https://nationalstemcellfoundation.org/glossary/aplastic-anemia/ |url-status=live |archive-url=https://web.archive.org/web/20220527215049/https://nationalstemcellfoundation.org/glossary/aplastic-anemia/#:~:text=Marie%20Curie%2C%20famous%20for%20her,radiation%20were%20not%20then%20known |archive-date=27 May 2022 |access-date=25 October 2024 |website=National Stem Cell Foundation|date=27 April 2017 }}</ref> though analysis of her levels of radium exposure done after her death find them within accepted safe levels and attribute her illness and death to her use of [[radiography]].<ref>{{cite journal |last=Butler |first=D. |date=14 September 1995 |title=X-rays, not radium, may have killed Curie |journal=Nature |volume=377 |issue=6545 |page=96 |bibcode=1995Natur.377...96. |doi=10.1038/377096b0 |pmid=7675094 |s2cid=186242763 |doi-access=free}}</ref> A significant amount of radium's danger comes from its daughter radon, which as a gas can enter the body far more readily than can its parent radium.<ref name=epa/>

===Regulation===
{{Further|History of radiation protection}}
The first published recommendations for protection against radium and radiation in general were made by the British X-ray and Radium Protection Committee and were adopted internationally in 1928 at the first meeting of the [[International Commission on Radiological Protection]] (ICRP), following preliminary guidance written by the [[Röntgen Society]].<ref>{{Cite journal|url=https://www.cmaj.ca/content/cmaj/159/11/1389.full.pdf |title=The early years of radiation protection: a tribute to Madame Curie |journal=CMAJ |first1=Arty R. |last1=Coppes-Zantinga |first2=Max J. |last2=Coppes |date=1 December 1998 |volume=159 |issue=11|pages=1389–1391 |pmid=9861210 |pmc=1229859 }}</ref> This meeting led to further developments of radiation protection programs<ref>{{Cite book|title=Radiation In Medicine: A Need For Regulatory Reform |chapter=History of Radiation Regulation in Medicine |editor-last1=Gottfried |editor-first1=KLD |editor-last2=Penn |editor-first2=G |location=Washington (DC) |publisher=National Academies Press (US) |date=1996 |url=https://www.ncbi.nlm.nih.gov/books/NBK232703/}}</ref> coordinated across all countries represented by the commission.<ref>{{Cite journal|journal=Annals of the ICRP |title=The History of ICRP and the Evolution of its Policies |first1=R.H. |last1=Clarke |first2=J. |last2=Valentin |url=https://www.icrp.org/docs/The%20History%20of%20ICRP%20and%20the%20Evolution%20of%20its%20Policies.pdf |date=2009}}</ref>

Exposure to radium is still regulated internationally by the ICRP, alongside the [[World Health Organization]].<ref>{{Cite book|url=https://www.ncbi.nlm.nih.gov/books/NBK595998/ |title=Toxicological Profile for Radium |location=Atlanta (GA) |publisher=Agency for Toxic Substances and Disease Registry (US) |date=December 7, 1990 |chapter=7. Regulations and Advisories}}</ref> The [[International Atomic Energy Agency]] (IAEA) publishes safety standards and provides recommendations for the handling of and exposure to radium in its works on [[naturally occurring radioactive material]]s and the broader International Basic Safety Standards,<ref>{{Cite web|url=https://world-nuclear.org/information-library/safety-and-security/radiation-and-health/naturally-occurring-radioactive-materials-norm |title=Naturally-Occurring Radioactive Materials (NORM) |website=World Nuclear Association |date=29 April 2024 }}</ref> which are not enforced by the IAEA but are available for adoption by members of the organization.<ref>{{Citation |url=https://www-pub.iaea.org/MTCD/publications/PDF/Pub1578_web-57265295.pdf |title=International Basic Safety Standards: General Safety Requirements Part 3 |work=Radiation Protection and Safety of Radiation Sources |publisher=IAEA |doi=10.61092/iaea.u2pu-60vm |date=July 2014|pages=1–436 |isbn=978-92-0-135310-8 |last5=Agency |first5=Oecd Nuclear Energy |last6=Organization |first6=Pan American Health |last8=Organization |first8=World Health }}</ref> In addition, in efforts to reduce the quantity of old [[radiotherapy]] devices that contain radium, the IAEA has worked since 2022<ref>{{Cite web|url=https://arao.si/en/arao-uspesno-izvozil-ra-226-v-kanado/ |title=ARAO successfully exports Ra-226 to Canada |date=29 July 2024 |website=ARAO Radioactive Waste Management}}</ref> to manage and recycle disused {{sup|226}}Ra sources.<ref>{{Cite web|url=https://world-nuclear-news.org/articles/canada-to-turn-radioactive-sources-from-thailand-i |title=Canada to turn radioactive sources from Thailand into cancer treatments |date=24 July 2024 |website=World Nuclear News}}</ref><ref>{{Cite web|url=https://www.iaea.org/newscenter/news/iaea-enables-safe-management-of-radium-226-legacy-sources |website=IAEA |title=IAEA Enables Safe Management of Radium-226 Legacy Sources |first1=Melissa |last1=Evans |first2=Zoe |last2=Dahse |date=5 April 2024}}</ref>

In several countries, further regulations exist and are applied beyond those recommended by the IAEA and ICRP. For example, in the United States, the [[Environmental Protection Agency]]-defined Maximum Contaminant Level for radium is 5&nbsp;pCi/L for drinking water;<ref>
{{cite report
 |title=EPA Facts about Radium
 |website=semspub.epa.gov
 |publisher=U.S. [[Environmental Protection Agency]]
 |url=https://semspub.epa.gov/work/11/176334.pdf
 |access-date=6 March 2023
}}</ref> at the time of the [[Manhattan Project]] in the 1940s, the "tolerance level" for workers was set at 0.1 micrograms of ingested radium.<ref>{{multiref2|{{cite book
 |author=Weisgall, Jonathan M.
 |year=1994
 |title=Operation Crossroads: The atomic tests at Bikini Atoll
 |publisher=Naval Institute Press
 |isbn=978-1-55750-919-2
 |page=[https://archive.org/details/operationcrossro0000weis/page/238 238]
 |url=https://archive.org/details/operationcrossro0000weis
 |url-access=registration |access-date=20 August 2011
}}|{{cite journal
 | first =Shirley A. | last =Fry
 | year = 1998
 | title = Supplement: Madame Curie's discovery of radium (1898): A commemoration by women in radiation sciences
 | journal = Radiation Research
 | volume= 150 | issue = 5 | page = S25
 | pmid = 9806606 | doi = 10.2307/3579805
 | jstor =3579805 | bibcode =1998RadR..150S..21F
}}
}}
</ref> The [[Occupational Safety and Health Administration]] does not specifically set exposure limits for radium, and instead limits ionizing radiation exposure in units of [[roentgen equivalent man]] based on the exposed area of the body. Radium sources themselves, rather than worker exposures, are regulated more closely by the [[Nuclear Regulatory Commission]],<ref>{{Cite web|url=https://www.osha.gov/ionizing-radiation/standards |title=Ionizing Radiation |website=Occupational Safety and Health Administration |access-date=August 13, 2024}}</ref> which requires licensing for anyone possessing {{sup|226}}Ra with activity of more than 0.01&nbsp;μCi.<ref>{{Cite web |date=October 2008 |title=Frequently Asked Questions (FAQs) Regarding Radium-226 |url=https://scp.nrc.gov/narmtoolbox/radium%20faq102008.pdf |access-date=12 October 2024 |website=U.S. Nuclear Regulatory Commission}}</ref> The particular governing bodies that regulate radioactive materials and nuclear energy are documented by the Nuclear Energy Agency for member countries<ref>{{Cite web |title=Legal frameworks for nuclear activities |url=https://www.oecd-nea.org/jcms/pl_24019/legal-frameworks-for-nuclear-activities |access-date=2024-10-22 |website=Nuclear Energy Agency (NEA) |language=en}}</ref> {{Endash}} for instance, in the [[Republic of Korea]], the nation's radiation safety standards are managed by the Korea Radioisotope Institute, established in 1985, and the Korea Institute of Nuclear Safety, established in 1990<ref>{{Cite journal |last=Kang |first=Keon Wook |date=February 2016 |title=History and Organizations for Radiological Protection |journal=Journal of Korean Medical Science |volume=31 Suppl 1 |issue=Suppl 1 |pages=S4–5 |doi=10.3346/jkms.2016.31.S1.S4 |issn=1598-6357 |pmc=4756341 |pmid=26908987}}</ref> {{Endash}} and the IAEA leads efforts in establishing governing bodies in locations that do not have government regulations on radioactive materials.<ref>{{Cite web |last1=Al Khatibeh |first1=Ahmad |last2=Dojcanova |first2=Lenka |date=2017-07-31 |title=IAEA Supports African Countries to Strengthen Regulatory Infrastructure |url=https://www.iaea.org/newscenter/news/iaea-supports-african-countries-to-strengthen-regulatory-infrastructure |access-date=2024-10-22 |website=www.iaea.org |language=en}}</ref><ref>{{Cite web |last1=Aksenova |first1=Nataliia |last2=Troubat |first2=Alix |date=2024-08-12 |title=Enhancing the Nuclear Legal Framework of the Republic of the Congo |url=https://www.iaea.org/newscenter/news/enhancing-the-nuclear-legal-framework-of-the-republic-of-the-congo |access-date=2024-10-22 |website=www.iaea.org |language=en}}</ref>

==Notes==
{{notelist}}

==References==
{{reflist|25em}}

===Bibliography===
{{sfn whitelist|CITEREFKellerWolfShani2011}}
* {{cite book
 |last1=Emsley
 |first1=John
 |date=2003
 |title=Nature's building blocks: an A-Z guide to the elements
 |publisher=Oxford University Press
 |isbn=978-0-19-850340-8
 |page=[https://archive.org/details/naturesbuildingb0000emsl/page/351 351&nbsp;ff]
 |url=https://archive.org/details/naturesbuildingb0000emsl
 |url-access=registration |access-date=27 June 2015
}}
* {{Greenwood&Earnshaw2nd}}
* {{Ullmann
 | first1=Cornelius |last1=Keller
 | first2=Walter    |last2=Wolf
 | first3=Jashovam  |last3=Shani
 | title = Radionuclides, 2. Radioactive Elements and Artificial Radionuclides
 | doi = 10.1002/14356007.o22_o15
 | date = 15 October 2011
 | pages=97–98
}}
* {{cite report
 |last1=Kirby    |first1=H.W.
 |last2=Salutsky |first2=Murrell L.
 |name-list-style=amp
 |date=December 1964
 |title=The Radiochemistry of Radium
 |series=crediting UNT Libraries Government Documents Department
 |url=https://digital.library.unt.edu/ark:/67531/metadc1027502/
 |via=[[University of North Texas]], UNT Digital Library
}} Alternate source: https://sgp.fas.org/othergov/doe/lanl/lib-www/books/rc000041.pdf

==Further reading==
{{refbegin|colwidth=25em|small=y}}

* {{cite web
 |author=Nanny Fröman
 |date=1 December 1996
 |title=Marie and Pierre Curie and the discovery of polonium and radium
 |publisher=[[Nobel Foundation]]
 |url=http://nobelprize.org/nobel_prizes/physics/articles/curie/index.html
 |access-date=25 December 2007
}}
* {{cite magazine
 |title = The great radium scandal
 |author = Macklis, R.M.
 |magazine = [[Scientific American]]
 |year = 1993
 |volume = 269 |issue = 2 |pages = 94–99
 |pmid = 8351514 |doi = 10.1038/scientificamerican0893-94
 |bibcode = 1993SciAm.269b..94M
}}
* {{cite Q|Q22920166)}} <!-- The Discovery of Radium -->
* {{cite book
 |author = Santos, Lucy Jane
 |title = Half Lives: The Unlikely History of Radium
 |date = 2020
 |publisher = Icon Books
 |isbn=9781785786082
 |oclc=1158229829
}}
{{refend}}

==External links==
{{Sister project links |wikt=radium |commons=radium |commonscat=yes |n=no |q=no |s=no |b=no |v=Radium atom}}

* {{cite web
 |title=The discovery of radium
 |date=8 July 2012
 |website=Lateral Science |place=UK
 |url=http://www.lateralscience.co.uk/radium/RaDisc.html
 |access-date=13 May 2017
 |archive-url=https://web.archive.org/web/20160309040715/http://lateralscience.blogspot.co.uk/2012/07/the-discovery-of-radium-by-marie-curie.html
 |archive-date=March 9, 2016
}}
* {{cite AV media
 |title=Radium water bath in Oklahoma
 |medium=photographic images
 |website=markwshead.com
 |url=http://www.markwshead.com/stuffHappens/radium.html
}}
* {{cite web
 |title=Radium, radioactive
 |website=NLM Hazardous Substances Databank
 |publisher=U.S. [[National Institutes of Health]]
 |url=http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@na+@rel+radium,+radioactive
}}
* {{cite web
 |title=Annotated bibliography for radium
 |website=Alsos Digital Library for Nuclear Issues
 |publisher=[[Washington and Lee University]]
 |place=Lexington, VA
 |url=http://alsos.wlu.edu/qsearch.aspx?browse=science/Radium
 |archive-url=https://web.archive.org/web/20190625210454/http://alsos.wlu.edu/qsearch.aspx?browse=science%2FRadium
 |archive-date=25 June 2019
}}
* {{cite web
 |title=Radium
 |website=[[The Periodic Table of Videos]]
 |publisher=[[University of Nottingham]]
 |url=http://www.periodicvideos.com/videos/088.htm
}}

{{Periodic table (navbox)}}
{{Marie & Pierre Curie}}
{{alkaline earth metals}}
{{Radium compounds}}
{{Subject bar
|portal1=Chemistry
|portal2=Medicine
|book1=Radium
|book2=Period 7 elements
|book3=Alkaline earth metals
|book4=Chemical elements (sorted&nbsp;alphabetically)
|book5=Chemical elements (sorted by number)
}}{{Authority control}}

[[Category:Radium| ]]
[[Category:Chemical elements]]
[[Category:Alkaline earth metals]]
[[Category:Chemical elements with body-centered cubic structure]]
[[Category:Marie Curie]]
[[Category:Pierre Curie]]