View source for Chemistry:Radium

{{infobox radium}}
[[File:Radium 226 radiation source 1.jpg|270 px|thumb|Radium 226 radiation source.<br>Activity 3300 Bq (3.3 kBq)]]
'''Radium''' is a [[Chemistry:Chemical element|chemical element]]; it has [[Chemistry:Chemical symbol|symbol]] '''Ra''' and [[Physics:Atomic number|atomic number]] 88. It is the sixth element in [[Chemistry:Alkaline earth metal|group&nbsp;2]] of the [[Chemistry:Periodic table|periodic table]], also known as the [[Chemistry:Alkaline earth metal|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 [[Physics:Radioactive|radioactive]], the most stable isotope being [[Physics:Radium-226|radium-226]] with a [[Physics:Half-life|half-life]] of 1,600&nbsp;years. When radium decays, it emits [[Physics:Ionizing radiation|ionizing radiation]] as a by-product, which can excite fluorescent chemicals and cause [[Physics:Radioluminescence|radioluminescence]].

Radium, in the form of [[Chemistry:Radium chloride|radium chloride]], was discovered by [[Biography:Marie Curie|Marie]] and [[Biography:Pierre Curie|Pierre Curie]] in 1898 from ore mined at [[Place:Jáchymov|Jáchymov]]. They extracted the radium compound from [[Chemistry:Uraninite|uraninite]] and published the discovery at the French Academy of Sciences five days later. Radium was isolated in its [[Chemistry:Metal|metal]]lic state by Marie Curie and [[Biography:André-Louis Debierne|André-Louis Debierne]] through the [[Chemistry:Electrolysis|electrolysis]] of radium chloride in 1911.<ref>{{cite web |title=Radium |department=Elements / Periodic Table |website=rsc.org |publisher=[[Organization:Royal Society of Chemistry|Royal Society of Chemistry]] |url=http://www.rsc.org/periodic-table/element/88/radium |access-date=5 July 2016 |url-status=live |archive-url=https://web.archive.org/web/20160324185543/http://www.rsc.org/periodic-table/element/88/Radium |archive-date=24 March 2016}}</ref>

In nature, radium is found in [[Chemistry:Uranium|uranium]] ores and (to a lesser extent) [[Chemistry:Thorium|thorium]] ores in trace amounts as small as a seventh of a gram per ton of uraninite. Radium is not necessary for 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 [[Chemistry:Calcium|calcium]]. {{As of|2014}}, other than its use in [[Medicine:Nuclear medicine|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. These applications have become obsolete owing to radium's toxicity; {{as of|lc=y|2020}}, less dangerous isotopes (of other elements) are instead used in radioluminescent devices.

==Bulk properties==
Radium is the heaviest known [[Chemistry:Alkaline earth metal|alkaline earth metal]] and is the only [[Physics:Radioactive|radioactive]] member of its group. Its physical and chemical properties most closely resemble its lighter [[Chemistry:Congener|congener]], [[Chemistry:Barium|barium]].<ref name=Greenwood-Earnshaw-1997>
<br/>
{{cite book
 |author2=Earnshaw, Alan
 |year=1997
 |title=Chemistry of the Elements |edition=2nd
 |publisher=Butterworth-Heinemann
 |isbn=978-0-08-037941-8
}}
</ref>{{rp|style=ama|p= 112}}

Pure radium is a [[Chemistry:Volatility|volatile]] silvery-white metal, although its lighter congeners [[Chemistry:Calcium|calcium]], [[Chemistry:Strontium|strontium]], and barium have a slight yellow tint.<ref name=Greenwood-Earnshaw-1997/>{{rp|style=ama|p= 112}} This tint rapidly vanishes on exposure to air, yielding a black layer of what is probably [[Chemistry:Radium nitride|radium nitride]] (Ra<sub>3</sub>N<sub>2</sub>).<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|p= 4}} Its [[Physics:Melting point|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.<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|p= 4}}
}} and its [[Physics:Boiling point|boiling point]] is {{convert|1737|°C}}; however, this is not well established.<ref name=brit/> Both of these values are slightly lower than those of barium, confirming periodic trends 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 [[Chemistry:Alkali metal|alkali metal]]s, radium crystallizes in the body-centered cubic structure at [[Standard temperature and pressure|standard temperature and pressure]]: the radium–radium bond distance is 514.8&nbsp;picometers.<ref>
{{cite journal
 | last1 = Weigel | first1 = F.
 | last2 = Trinkl | first2 = A.
 | year = 1968
 | title = Zur Kristallchemie des Radiums | lang = 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</sup>, higher than that of barium, again confirming periodic trends; the radium-barium density ratio is comparable to the radium-barium atomic mass ratio,<ref name=Young>
{{cite book
 |author=Young, David A.
 |year=1991
 |chapter=Radium
 |title=Phase Diagrams of the Elements
 |publisher=University of California Press
 |isbn=978-0-520-91148-2
 |page=85
 |chapter-url=https://books.google.com/books?id=F2HVYh6wLBcC&pg=PA85
}}
</ref>
due to the two elements' similar crystal structures.<ref name=Young/><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|Physics:Isotopes of radium}}
[[File:Decay chain(4n+2, Uranium series).svg|thumb|upright=1.25|left|[[Physics:Decay chain|Decay chain]] of <sup>238</sup>U, the primordial progenitor of <sup>226</sup>Ra]]
Radium has 33&nbsp;known isotopes, with [[Chemistry:Mass number|mass number]]s from 202 to 234: all of them are [[Physics:Radioactive|radioactive]].{{NUBASE2020|ref}} Four of these – [[Chemistry:Radium-223|<sup>223</sup>Ra]] ([[Physics:Half-life|half-life]] 11.4&nbsp;days), <sup>224</sup>Ra (3.64&nbsp;days), <sup>226</sup>Ra (1600&nbsp;years), and <sup>228</sup>Ra (5.75&nbsp;years) – occur naturally in the [[Physics:Decay chain|decay chain]]s of primordial [[Physics:Thorium-232|thorium-232]], [[Physics:Uranium-235|uranium-235]], and [[Physics:Uranium-238|uranium-238]] (<sup>223</sup>Ra from uranium-235, <sup>226</sup>Ra from uranium-238, and the other two from thorium-232). These isotopes nevertheless still have half-lives too short to be [[Chemistry:Primordial nuclide|primordial radionuclides]] and only exist in nature from these decay chains.<ref name=Kirby-Salutsky-1964>
<br/>
{{cite report
 |last1=Kirby    |first1=H.W.
 |last2=Salutsky |first2=Murrell L.
 |name-list-style=amp
 |date=December 1964b
 |title=The Radiochemistry of Radium
 |series=crediting UNT Libraries Government Documents Department
 |url=https://digital.library.unt.edu/ark:/67531/metadc1027502/
 |via=[[Organization:University of North Texas|University of North Texas]], UNT Digital Library
}}
: ''alternate source''
{{cite report
 | last1 = Kirby    | first1 = H.W.
 | last2 = Salutsky | first2 = Murrell L.
 | name-list-style = amp
 | year = 1964a
 | title = The Radiochemistry of Radium
 | publisher = National Academies Press
 | page = 3
 | url = https://sgp.fas.org/othergov/doe/lanl/lib-www/books/rc000041.pdf
 | via = sgp.fas.org
 | ref=Kirby
}}
</ref>{{rp|style=ama|p= 3}}
Together with the mostly [[Physics:Synthetic radioisotope|artificial]] <sup>225</sup>Ra (15&nbsp;d), which occurs in nature only as a decay product of minute traces of [[Physics:Neptunium-237|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=[[Organization:Journal of the American Chemical Society|Journal of the American Chemical Society]]
 |volume=74 |issue=23 |pages=6081–6084
 |doi=10.1021/ja01143a074
 |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}} At least 12&nbsp;[[Physics:Nuclear isomer|nuclear isomer]]s have been reported; the most stable of them is radium-205m, with a half-life between 130~230&nbsp;milliseconds; this is still shorter than twenty-four [[Physics:Ground state|ground-state]] radium isotopes.{{NUBASE2020|ref}}

In the early history of the study of radioactivity, the different natural isotopes of radium were given different names. In this scheme, <sup>223</sup>Ra was named actinium&nbsp;X (AcX), <sup>224</sup>Ra thorium&nbsp;X (ThX), <sup>226</sup>Ra radium (Ra), and <sup>228</sup>Ra mesothorium 1 (MsTh<sub>1</sub>).<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|p= 3}} When it was realized that all of these are isotopes of the same element, many of these names fell out of use, and "radium" came to refer to all isotopes, not just <sup>226</sup>Ra. Some of radium-226's decay products received historical names including "radium", ranging from radium&nbsp;{{sc|A}} to radium&nbsp;{{sc|G}}, with the letter indicating approximately how far they were down the chain from their parent <sup>226</sup>Ra: {{nobr|Radium emanation {{=}} {{sup|222}}Rn,}} {{nobr|Ra&nbsp;{{sc|A}} {{=}} {{sup|218}}Po,}} {{nobr|Ra&nbsp;{{sc|B}} {{=}} {{sup|214}}Pb,}} {{nobr|Ra&nbsp;{{sc|C}} {{=}} {{sup|214}}Bi,}} {{nobr|Ra&nbsp;{{sc|C}}{{sub|1}} {{=}} {{sup|214}}Po,}} {{nobr|Ra&nbsp;{{sc|C}}{{sub|2}} {{=}} {{sup|210}}Tl,}} {{nobr|Ra&nbsp;{{sc|D}} {{=}} {{sup|210}}Pb,}} {{nobr|Ra&nbsp;{{sc|E}} {{=}} {{sup|210}}Bi,}} {{nobr|Ra&nbsp;{{sc|F}} {{=}} {{sup|210}}Po,}} and {{nobr|Ra&nbsp;{{sc|G}} {{=}} {{sup|206}}Pb .}}<ref>
{{cite journal
 |last=Kuhn |first=W.
 |year=1929
 |title=LXVIII. Scattering of thorium&nbsp;{{sc|C}}″ γ-radiation by radium&nbsp;{{sc|G}} and ordinary lead
 |journal=The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science
 |volume=8 |issue=52 |page=628
 |doi=10.1080/14786441108564923 |issn=1941-5982
}}
</ref>

<sup>226</sup>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 [[Chemistry:Noble gas|noble gas]] [[Chemistry:Radon|radon]] (specifically the isotope [[Physics:Radon-222|<sup>222</sup>Rn]]), which is responsible for much of the danger of environmental radium.<ref name=epa/> It is 2.7&nbsp;million times more radioactive than the same [[Physics:Amount of substance|molar amount]] of natural [[Chemistry:Uranium|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 [[Physics:Temperature|temperature]] than its surroundings because of the radiation it emits – alpha particles, beta particles, and gamma rays. More specifically, natural radium (which is mostly <sup>226</sup>Ra) emits mostly alpha particles, but other steps in its decay chain (the [[Physics: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>

In 2013, it was discovered at [[Organization:CERN|CERN]] that the nucleus of radium-224 is pear-shaped using a technique called [[Physics:Coulomb excitation|coulomb excitation]]. This was the first discovery of an asymmetric nucleus.<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> This is a strong circumstantial evidence that certain heavy, unstable atomic nuclei have distorted nuclei, in this case, a pear shape.<ref>{{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, like barium, is a highly [[Chemistry:Reactivity|reactive]] metal and always exhibits its group oxidation state of +2.<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|p= 4}} It forms the colorless Ra<sup>2+</sup> cation in [[Chemistry:Aqueous solution|aqueous solution]], which is highly [[Chemistry:Base|basic]] and does not form [[Chemistry:Coordination complex|complexes]] readily.<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|p= 4}} Most radium compounds are therefore simple ionic compounds,<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|p= 4}} though participation from the 6s and 6p electrons (in addition to the valence 7s electrons) is expected due to [[Chemistry:Relativistic quantum chemistry|relativistic effects]] and would enhance the [[Chemistry:Covalent bond|covalent]] character of radium compounds such as Ra[[Chemistry:Fluorine|F]]<sub>2</sub> and Ra[[Chemistry:Astatine|At]]<sub>2</sub>.<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 }}</ref> For this reason, the [[Chemistry:Standard electrode potential|standard electrode potential]] for the half-reaction Ra<sup>2+</sup> (aq) + 2e<sup>−</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).<ref name=Greenwood-Earnshaw-1997/>{{rp|style=ama|p= 111}} The values for barium and radium are almost exactly the same as those of the heavier alkali metals [[Chemistry:Potassium|potassium]], [[Chemistry:Rubidium|rubidium]], and [[Chemistry:Caesium|caesium]].<ref name=Greenwood-Earnshaw-1997/>{{rp|style=ama|p= 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-[[Physics:Radiolysis|radiolysis]] from radium's [[Physics:Alpha decay|alpha decay]].<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|p= 4}} Insoluble radium compounds [[Chemistry:Coprecipitation|coprecipitate]] with all barium, most [[Chemistry:Strontium|strontium]], and most [[Chemistry:Lead|lead]] compounds.<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|p= 8}}

[[Chemistry:Radium oxide|Radium oxide]] (RaO) has not been characterized well past its existence, despite oxides being common compounds for the other alkaline earth metals. [[Chemistry:Radium hydroxide|Radium hydroxide]] (Ra(OH)<sub>2</sub>) is the most readily soluble among the alkaline earth hydroxides and is a stronger base than its barium congener, [[Chemistry:Barium hydroxide|barium hydroxide]].<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|pp= 4–8}} It is also more soluble than actinium hydroxide and thorium hydroxide: these three adjacent hydroxides may be separated by precipitating them with [[Chemistry:Ammonia|ammonia]].<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|pp= 4–8}}

[[Chemistry:Radium chloride|Radium chloride]] (RaCl<sub>2</sub>) is a colorless, luminous 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.<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|pp= 4–8}} It is soluble in water, though less so than [[Chemistry:Barium chloride|barium chloride]], and its solubility decreases with increasing concentration of [[Chemistry:Hydrochloric acid|hydrochloric acid]]. Crystallization from aqueous solution gives the dihydrate RaCl<sub>2</sub>·2H<sub>2</sub>O, isomorphous with its barium analog.<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|pp= 4–8}}

[[Chemistry:Radium bromide|Radium bromide]] (RaBr<sub>2</sub>) is also a colorless, luminous compound.<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|pp= 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 [[Chemistry:Nitrogen|nitrogen]] molecules in the air, making it glow. The [[Physics:Alpha particle|alpha particle]]s emitted by radium quickly gain two electrons to become neutral [[Chemistry:Helium|helium]], which builds up inside and weakens radium bromide crystals. This effect sometimes causes the crystals to break or even explode.<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|pp= 4–8}}

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

Radium forms much the same insoluble salts as its lighter congener barium: it forms the insoluble [[Chemistry:Radium sulfate|sulfate]] (RaSO<sub>4</sub>, the most insoluble known sulfate), chromate (RaCrO<sub>4</sub>), [[Chemistry:Radium carbonate|carbonate]] (RaCO<sub>3</sub>), [[Chemistry:Radium iodate|iodate]] (Ra(IO<sub>3</sub>)<sub>2</sub>), 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, oxalate, and sulfite are probably also insoluble, as they [[Chemistry:Coprecipitation|coprecipitate]] with the corresponding insoluble barium salts.<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|pp= 8–9}} The great insolubility of radium sulfate (at 20&nbsp;°C, only 2.1&nbsp;mg will dissolve in 1&nbsp;[[Kilogram|kg]] of water) means that it is one of the less biologically dangerous radium compounds.<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|p= 12}} The large ionic radius of Ra<sup>2+</sup> (148&nbsp;pm) results in weak complexation and poor extraction of radium from aqueous solutions when not at high pH.<ref name="Ullmann97" />

==Occurrence==
All isotopes of radium have half-lives much shorter than the [[Earth:Age of the Earth|age of the Earth]], so that any primordial radium would have decayed long ago. Radium nevertheless still occurs [[Physics:Radium and radon in the environment|in the environment]], as the isotopes <sup>223</sup>Ra, <sup>224</sup>Ra, <sup>226</sup>Ra, and <sup>228</sup>Ra are part of the decay chains of natural thorium and uranium isotopes; since thorium and uranium have very long half-lives, these [[Physics:Decay product|daughters]] are continually being regenerated by their decay.<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|p= 3}} Of these four isotopes, the longest-lived is <sup>226</sup>Ra (half-life 1600&nbsp;years), a decay product of natural uranium. Because of its relative longevity, <sup>226</sup>Ra is the most common isotope of the element, making up about one part per trillion of the Earth's crust; essentially all natural radium is <sup>226</sup>Ra.<ref name=Greenwood-Earnshaw-1997/>{{rp|style=ama|pp=109–110}} Thus, radium is found in tiny quantities in the uranium ore [[Chemistry:Uraninite|uraninite]] and various other uranium minerals, and in even tinier quantities in thorium minerals. One [[Ton|ton]] of [[Chemistry:Uraninite|pitchblende]] typically yields about one seventh of a [[Gram|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:Earth's crust|Earth's crust]] contains about 900&nbsp;picograms of radium, and one liter of sea water contains about 89&nbsp;femtograms 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.), ''[[Physics:CRC Handbook of Chemistry and Physics|CRC Handbook of Chemistry and Physics]], 85th Edition''. CRC Press. Boca Raton, Florida (2005).</ref>

==History==
[[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 discovered by [[Biography:Marie Curie|Marie Skłodowska-Curie]] and her husband [[Biography:Pierre Curie|Pierre Curie]] on 21 December 1898, in a [[Chemistry:Uraninite|uraninite]] (pitchblende) sample from [[Place:Jáchymov|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 [[Chemistry:Bismuth|bismuth]] which turned out to be [[Chemistry:Polonium|polonium]]. They then isolated a radioactive mixture consisting of two components: compounds of [[Chemistry:Barium|barium]], which gave a brilliant green flame color, and unknown radioactive compounds which gave [[Carmine (color)|carmine]] [[Physics:Spectral line|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>{{cite journal |year=1898 |title=Sur une nouvelle substance fortement radio-active, contenue dans la pechblende (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 }}</ref><ref>{{cite journal | doi = 10.1021/ed010p79 | title = The discovery of the elements. XIX. The radioactive elements |year = 1933 | last1 = Weeks | first1 = Mary Elvira | 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 power of emitting energy in the form of rays.<ref>{{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}}</ref><ref name=Carvalho2011>{{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}}</ref><ref name="Weeks1933">{{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>

In September 1910, Marie Curie and [[Biography:André-Louis Debierne|André-Louis Debierne]] announced that they had isolated radium as a pure [[Chemistry:Metal|metal]] through the [[Chemistry:Electrolysis|electrolysis]] of pure radium [[Chemistry:Chloride|chloride]] (RaCl<sub>2</sub>) solution using a [[Chemistry:Mercury (element)|mercury]] [[Physics:Cathode|cathode]], producing radium–mercury [[Chemistry:Amalgam|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 [[Chemistry:Hydrogen|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 |lang=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. Eoler isolated radium by [[Physics:Thermal decomposition|thermal decomposition]] of its [[Chemistry:Azide|azide]], Ra(N<sub>3</sub>)<sub>2</sub>.<ref name=Kirby-Salutsky-1964/>{{rp|style=ama|p= 3}} Radium metal was first industrially produced at the beginning of the 20th century by Biraco, a subsidiary company of [[Company:Union Minière du Haut Katanga|Union Minière du Haut Katanga]] (UMHK) in its 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 general historical unit for radioactivity, the [[Physics:Curie (unit)|curie]], is based on the radioactivity of <sup>226</sup>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 slightly refined to be {{val|3.7|e=10|u=disintegrations per second}}.

===Historical applications===
====Luminescent paint====
[[File:Radium 2.jpg|thumb|Radium watch hands under ultraviolet light]]
Radium was formerly used in [[Physics:Luminescence|self-luminous]] paints for watches, nuclear panels, aircraft switches, clocks, and instrument dials. A typical self-luminous watch that uses radium paint contains around 1 microgram of radium.<ref name=PMC2024184/> In the mid-1920s, a lawsuit was filed against the United States Radium Corporation by five dying "[[Physics:Radium Girls|Radium Girls]]" – dial painters who had painted radium-based [[Physics:Luminous paint|luminous paint]] on the dials of watches and clocks. 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, [[Medicine:Anemia|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 [[Medicine:Syphilis|syphilis]]. This complete disregard for employee welfare had a significant impact on the formulation of occupational disease labor law.<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, the adverse effects of radioactivity became widely known, and radium-dial painters were instructed in proper safety precautions and provided with protective gear. In particular, dial painters no longer licked paint brushes to shape them (which caused some ingestion of radium salts). Radium was still used in dials as late as the 1960s, but there were no further injuries to dial painters. This highlighted that the harm to the Radium Girls could easily have been avoided.<ref>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</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 [[Chemistry:Promethium|promethium]]-147 (half-life 2.6 years) or [[Physics:Tritium|tritium]] (half-life 12 years) paint was used; both continue to be used as of 2004.<ref>{{Cite book|title = Man-made and natural radioactivity in environmental pollution and radiochronology|date = 2004|page = 78|isbn = 978-1-4020-1860-2|last1 = Tykva|first1 = Richard|last2 = Berg|first2 = Dieter|publisher=Springer}}</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=[[Company:Nauka (publisher)|Nauka]] |page=118}}</ref> Tritium emits very low-energy beta radiation (even lower-energy than the beta radiation emitted by promethium)<ref name=NUBASE2016><br/>{{NUBASE2016}}</ref> which cannot penetrate the skin,<ref>
{{cite report
 |title=Hydrogen-3
 |series=Nuclide safety data sheet
 |publisher=Environmenal Health & Safety Office, [[Organization:Emory University|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> rather than the penetrating gamma radiation of radium, and is regarded as safer.<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>

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; however, 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.<ref name=emsley>
<br/>
{{cite book
 |author=Emsley, 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
}}
</ref>
The appearance of an often thick layer of green or yellowish brown paint in devices from this period suggests a radioactive hazard. The radiation dose from an intact device is relatively low and usually not an acute risk; but the paint is dangerous if released and inhaled or ingested.<ref name=brit>
{{cite encyclopedia
 |title=Radium
 |encyclopedia=[[Encyclopædia Britannica]]
 |url=http://global.britannica.com/EBchecked/topic/489270/radium-Ra 
  <!-- presumed -->
 |archive-url=https://web.archive.org/web/20130615033023/http://global.britannica.com/EBchecked/topic/489270/radium-Ra
 |archive-date=2013-06-15  }}
</ref><ref>
{{cite web
 |title=Luminous radium paint
 |website=vintagewatchstraps.com
 |url=http://www.vintagewatchstraps.com/luminous.htm
 |archive-url=https://web.archive.org/web/20130304002823/http://www.vintagewatchstraps.com/luminous.htm
 |archive-date=4 March 2013
}}
</ref>

====Commercial use====

Radium was once an additive in products such as toothpaste, hair creams, and even food items due to its supposed curative powers.<ref>{{cite web|access-date=1 August 2009|title=French Web site featuring products (medicines, mineral water, even underwear) containing radium|url=http://www.dissident-media.org/infonucleaire/radieux.html|archive-url=https://web.archive.org/web/20110315181647/http://www.dissident-media.org/infonucleaire/radieux.html|archive-date=15 March 2011|url-status=live}}</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, ''[[Chemistry:Radithor|Radithor]]'' or ''Revigator'' types of "radium water" or "Standard Radium Solution for Drinking".)<ref name=emsley/> Spas featuring radium-rich water are still occasionally touted as beneficial, such as those in Misasa, Tottori, Japan. In the U.S., nasal radium irradiation was also administered to children to prevent middle-ear problems or enlarged tonsils from the late 1940s through the early 1970s.<ref name=Baltimore>
{{cite news
 |last=Cherbonnier |first=Alice
 |date=1 October 1997
 |title=Nasal radium irradiation of children has health fallout
 |newspaper=Baltimore Chronicle
 |url=http://baltimorechronicle.com/rupnose.html
 |access-date=1 August 2009 |url-status=live
 |archive-url=https://web.archive.org/web/20110928021006/http://www.baltimorechronicle.com/rupnose.html
 |archive-date=28 September 2011
}}
</ref>

====Medical use====
[[File:Radior_cosmetics_containing_radium_1918.jpg|thumb|1918 ad for Radior cosmetics, which the manufacturer claimed contained radium.]]

Radium (usually in the form of [[Chemistry:Radium chloride|radium chloride]] or [[Chemistry:Radium bromide|radium bromide]]) was used in [[Medicine:Medicine|medicine]] to produce radon gas, which in turn was used as a [[Medicine:Cancer|cancer]] treatment; for example, several of these radon sources were used in Canada in the 1920s and 1930s.<ref name=brit/><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 [[Biology: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 [[Physics:Cobalt-60|<sup>60</sup>Co]], which is less costly and available in larger quantities, are usually used to replace the historical use of radium in this application.<ref name="Ullmann97" />

Early in the 1900s, biologists used radium to induce mutations and study [[Biology:Genetics|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. [[Biography:Thomas Hunt Morgan|Thomas Hunt Morgan]] used radium to induce changes resulting in white-eyed fruit flies.
Nobel-winning biologist [[Biography: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|title=The Secrets of Life: Historian Luis Campos resurrects radium's role in early genetics research|journal=Distillations|date=2016|volume=2|issue=2|pages=44–45|url=https://www.sciencehistory.org/distillations/magazine/the-secrets-of-life|access-date=22 March 2018|archive-url=https://web.archive.org/web/20180323154857/https://www.sciencehistory.org/distillations/magazine/the-secrets-of-life|archive-date=23 March 2018|url-status=live}}</ref>

Howard Atwood Kelly, one of the founding physicians of Johns Hopkins Hospital, was a major pioneer in the medical use of radium to treat cancer.<ref>
{{cite web
 | title = The Four Founding Physicians
 | department = About / History
 | website = Hopkins Medicine (hopkinsmedicine.org)
 | publisher = Johns Hopkins School of Medicine, [[Organization:Johns Hopkins University|Johns Hopkins University]]
 | url = http://www.hopkinsmedicine.org/about/history/history5.html
 | access-date = 10 April 2013 | url-status = live
 | archive-url = https://web.archive.org/web/20150310220741/http://www.hopkinsmedicine.org/about/history/history5.html
 | archive-date = 10 March 2015
}}
</ref>
His first patient was his own aunt in 1904, who died shortly after surgery.<ref name=DasturTank2011>
{{cite journal
 |last1=Dastur |first1=Adi E.
 |last2=Tank   |first2=P.D.
 |year=2011
 |title=Howard Atwood Kelly: Much beyond the stitch
 |journal=The Journal of Obstetrics and Gynecology of India
 |volume=60 |issue=5 |pages=392–394
 |doi=10.1007/s13224-010-0064-6 |pmc=3394615
}}
</ref>
Kelly was known to use excessive amounts of radium to treat various cancers and tumors. As a result, some of his patients died from radium exposure.<ref name=AronowitzRobison2010>
{{cite journal
 |last1=Aronowitz |first1=Jesse N.
 |last2=Robison |first2=Roger F.
 |year=2010
 |title=Howard Kelly establishes gynecologic brachytherapy in the United States
 |journal=Brachytherapy
 |volume=9 |issue=2 |pages=178–184
 |doi=10.1016/j.brachy.2009.10.001 |pmid=20022564
}}
</ref>
His method of radium application was inserting a radium capsule near the affected area, then sewing the radium "points" directly to the tumor.<ref name=AronowitzRobison2010/> This was the same method used to treat Henrietta Lacks, the host of the original HeLa cells, for [[Medicine:Cervical cancer|cervical cancer]].<ref name=Skloot2010>
{{cite book
 |author=Skloot, Rebecca
 |date=2 February 2010
 |title=The Immortal Life of Henrietta Lacks
 |publisher=Random House Digital
 |isbn=978-0-307-58938-5
 |url=https://books.google.com/books?id=LBBhikJpLjwC
 |access-date=8 April 2013 |url-status=live
 |archive-url=https://web.archive.org/web/20130617115412/http://books.google.com/books?id=LBBhikJpLjwC
 |archive-date=17 June 2013
}}
</ref>
As of 2015, safer and more available radioisotopes are used instead.<ref name=epa/>

==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 only large source for uranium ore was the [[Chemistry:Silver|silver]] mines in [[Place:Jáchymov|Jáchymov]], [[Place:Austria-Hungary|Austria-Hungary]] (now [[Place:Czech Republic|Czech Republic]]).<ref name="crc" /> The uranium ore was only a byproduct of the mining activities.<ref name="Ceranski">{{cite journal | doi = 10.1007/s00048-008-0308-z | title = Tauschwirtschaft, Reputationsökonomie, Bürokratie |year = 2008 | last1 = Ceranski | first1 = Beate | journal = NTM Zeitschrift für Geschichte der Wissenschaften, Technik und Medizin | volume = 16 | issue = 4 | pages = 413–443| 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 [[Chemistry:Sulfuric acid|sulfuric acid]] leaving radium sulfate, which is similar to [[Chemistry:Barium sulfate|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 [[Chemistry:Hydrochloric acid|hydrochloric acid]] treatment to minimize impurities of other compounds. The remaining residue was then treated with [[Chemistry:Sodium carbonate|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 [[Chemistry:Fractional crystallization|fractional crystallisation]] while monitoring the progress using a spectroscope (radium gives characteristic red lines in contrast to the green barium lines), and the [[Physics:Electroscope|electroscope]].<ref>[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 [[Place:Jáchymov|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 [[Finance: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. The [[Chemistry:Carnotite|Carnotite]] sands in Colorado provide some of the element, but richer ores are found in the Congo and the area of the Great Bear Lake and the Great Slave Lake of northwestern Canada. Neither of the deposits is mined for radium but the uranium content makes mining profitable.<ref name="crc" /><ref>{{cite journal | jstor = 40796935|author=Just, Evan|author2=Swain, Philip W.|author3=Kerr, William A.|name-list-style=amp |journal=Financial Analysts Journal|volume=8|issue=1|year=1952 |pages=85–93|title=Peacetíme Impact of Atomíc Energy | doi = 10.2469/faj.v8.n1.85}}</ref>

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 it is easy to add some to carry the radium. These processes were applied to high grade uranium ores but may not work 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,<ref name=Greenwood-Earnshaw-1997/>{{rp|style=ama|pp= 109–110}} but as of 2011, they are extracted only from spent nuclear fuel.<ref name=emsley/>{{rp|style=ama|p=437}}
In 1954, the total worldwide supply of purified radium amounted to about {{convert|5|lb|kg}}<ref name=PMC2024184>
{{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> and it is still in this range in 2015, while the annual production of pure radium compounds is only about 100&nbsp;g in total as of 1984.<ref name=Greenwood-Earnshaw-1997/>{{rp|style=ama|pp= 109–110}} The chief radium-producing countries are Belgium, Canada, the Czech Republic, Slovakia, the United Kingdom, and Russia.<ref name=Greenwood-Earnshaw-1997/>{{rp|style=ama|pp= 109–110}} The amounts of radium produced were and are always relatively small; for example, in 1918, 13.6&nbsp;g of radium were produced in the United States.<ref>{{cite journal | doi = 10.1126/science.49.1262.227 | title = Radium Production |year = 1919 | last = Viol | first = C.H. | journal = Science | volume = 49 | issue = 1262 | pages = 227–228 | pmid = 17809659|bibcode = 1919Sci....49..227V | url = https://zenodo.org/record/1448223 }}</ref> The metal is isolated by reducing radium oxide with aluminium metal in a vacuum at 1,200&nbsp;°C.<ref name="Ullmann97" />

==Modern applications==
Radium is seeing increasing use in the field of [[Physics:Atomic, molecular, and optical physics|atomic, molecular, and optical physics]]. Symmetry breaking forces scale proportional to <math>\ Z^3\ ,</math><ref>{{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 }}</ref><ref>{{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 [[Physics:Standard Model|standard model]]. Some radium isotopes, such as radium-225, have octupole deformed parity doublets that enhance sensitivity to [[Physics:CP violation|charge parity violating]] new physics by two to three orders of magnitude compared to <sup>199</sup>Hg.<ref>
{{cite journal
 |title=Nuclear Time-Reversal Violation and the Schiff Moment of $^{225}\mathrm{Ra}$
 |first1=J. |last1=Dobaczewski
 |first2=J. |last2=Engel
 |date=13 June 2005
 |journal=[[Physics:Physical Review Letters|Physical Review Letters]]
 |volume=94 |issue=23 |page=232502
 |doi=10.1103/PhysRevLett.94.232502 |pmid=16090465
 |arxiv=nucl-th/0503057 |s2cid=328830
 |url=https://link.aps.org/doi/10.1103/PhysRevLett.94.232502
 |via=APS.org
}}
</ref><ref>
{{cite journal
 |first1=B. |last1=Graner |first2=Y. |last2=Chen
 |first3=E.G. |last3=Lindahl |first4=B.R. |last4=Heckel
 |date=18 April 2016
 |title=Reduced limit on the permanent electric dipole moment of {{sup|199}}{{math|Hg}}
 |journal=Physical Review Letters
 |volume=116 |issue=16 |page=161601
 |doi=10.1103/PhysRevLett.116.161601  |pmid=27152789
 |arxiv=1601.04339  |s2cid=2230011
 |url=https://link.aps.org/doi/10.1103/PhysRevLett.116.161601
 |via=APS.org
}}
</ref><ref>
{{cite journal
 |first1=R.H.  |last1=Parker         |first2=M.R.   |last2=Dietrich
 |first3=M.R.  |last3=Kalita         |first4=N.D.   |last4=Lemke
 |first5=K.G.  |last5=Bailey         |first6=M.     |last6=Bishof
 |first7=J.P.  |last7=Greene         |first8=R.J.   |last8=Holt
 |first9=W.    |last9=Korsch         |first10=Z.-T. |last10=Lu
 |first11=P.   |last11=Mueller       |first12=T.P.  |last12=O'Connor
 |first13=J.T. |last13=Singh
 |display-authors=6
 |date=9 June 2015
 |title=First measurement of the atomic electric dipole moment of {{sup|225}}{{math|Ra}}
 |journal=[[Physics:Physical Review Letters|Physical Review Letters]]
 |volume=114  |issue=23  |page=233002
 |doi=10.1103/PhysRevLett.114.233002  |pmid=26196797
 |arxiv=1504.07477  |s2cid=41982867
 |url=https://link.aps.org/doi/10.1103/PhysRevLett.114.233002
 |via=APS.org
}}
</ref>

Radium is also a promising candidate for trapped ion [[Engineering:Atomic clock#Optical clocks|optical clocks]].  The radium ion has two subhertz-linewidth transitions from the <math>\ \mathrm{ 7s^2S_{\tfrac{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</sup>Ra+ trapped ion atomic clock has been demonstrated on the <math>\ \mathrm{ 7s^2S_{\tfrac{1}{2}} }\ </math> to <math>\ \mathrm{ 6d^2D_{\tfrac{5}{2}} }\ </math> transition.<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> Additionally, radium is particularly well suited for a transportable optical clock as all transitions necessary for clock operation can be addressed with direct diode lasers at common wavelengths.

Some of the few practical uses of radium are derived from its radioactive properties. More recently discovered radioisotopes, such as [[Physics:Cobalt-60|cobalt-60]] and [[Physics:Caesium-137|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>
{{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
 | place = Washington, DC
 | isbn = 978-0-309-11014-3
 | page = 24
 | url = https://books.google.com/books?id=3cT2REdXJ98C&pg=PA24
 | access-date = 27 June 2015 | url-status = live | via = Google Books
 | archive-url = https://web.archive.org/web/20150905164805/https://books.google.com/books?id=3cT2REdXJ98C&pg=PA24
 | archive-date = 5 September 2015
}}
</ref><ref>
{{cite book
 | last1 = Bentel | first1 = Gunilla Carleson
 | year = 1996
 | title = Radiation therapy planning
 | isbn = 978-0-07-005115-7
 | page = 8
 | publisher = McGraw Hill Professional
 | url = https://books.google.com/books?id=bk0go_-FO5QC&pg=PA8
 | access-date = 27 June 2015 | url-status = live  | via = Google Books
 | archive-url = https://web.archive.org/web/20150905174312/https://books.google.com/books?id=bk0go_-FO5QC&pg=PA8
 | archive-date = 5 September 2015
}}
</ref>

The isotope <sup>223</sup>Ra (the chloride is under the trade name Xofigo)<ref>{{cite web |title=Xofigo US Patent |url=https://www.xofigo-us.com/ |website=Xofigo |access-date=28 September 2022}}</ref> was approved by the United States [[Organization:Food and Drug Administration|Food and Drug Administration]] in 2013 for use in [[Medicine:Medicine|medicine]] as a [[Medicine:Cancer|cancer]] treatment of bone [[Medicine:Metastasis|metastasis]].<ref name="FBT-FDA2013">{{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 }}</ref><ref>{{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 with Xofigo is the therapy of bony metastases from castration-resistant prostate cancer due to the favourable characteristics of this alpha-emitter radiopharmaceutical.<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
}}
</ref>
<sup>225</sup>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 is still used in 2007 as a radiation source in some [[Physics:Industrial radiography|industrial radiography]] devices to check for flawed metallic parts, similarly to X-ray imaging.<ref name=epa/> When mixed with [[Chemistry:Beryllium|beryllium]], radium acts as a [[Physics:Neutron source|neutron source]].<ref name=emsley/><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> {{As of|2004}}, radium-beryllium neutron sources are still sometimes used,<ref name=epa>
<br/>
{{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
 | last1 = Holden | first1 = N.E.     | last2 = Reciniello | first2 = R.N.
 | last3 = Hu     | first3 = J.P.     | last4 = Rorer      | first4 = David C.
 | 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
 | url = http://www.bnl.gov/isd/documents/24293.pdf
 | 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 [[Chemistry:Polonium|polonium]] are more common: about 1,500 polonium-beryllium neutron sources, with an individual activity of {{convert|1850|Ci|TBq|abbr=on}}, have been used annually in {{wipe|Russia}}. These 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</sup> neutrons per second) in favour of [[Physics:Americium-241|<sup>241</sup>Am]]–Be sources.<ref name=Ullmann97/> {{As of|2011}}, the isotope <sup>226</sup>Ra is mainly used to form <sup>227</sup>[[Chemistry:Actinium|Ac]] by neutron irradiation in a nuclear reactor.<ref name=Ullmann97/>

==Hazards==
Radium is highly radioactive, and its immediate daughter, [[Chemistry:Radon|radon]] gas, is also radioactive. When ingested, 80% of the ingested radium leaves the body through the [[Biology:Feces|feces]], while the other 20% goes into the bloodstream, mostly accumulating in the bones. This is because the body treats radium as [[Chemistry:Calcium|calcium]] and [[Physics:Bone seeker|deposits it in the bones]], where radioactivity degrades [[Biology: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 [[Physics:Gamma ray|gamma ray]]s upon their decay, which kill and mutate cells.<ref name=epa/> At the time of the [[Physics:Manhattan Project|Manhattan Project]] in 1944, the "tolerance dose" for workers was set at 0.1 micrograms of ingested radium.<ref>
{{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
}}
</ref><ref>
{{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 | pages = S21–S29
 | pmid = 9806606 | doi = 10.2307/3579805
 | jstor =3579805 | bibcode =1998RadR..150S..21F
}}
</ref><!-- 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 ulcerated. Pierre and Marie Curie were so intrigued by radiation that they sacrificed their own health to learn more about it. 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 [[Medicine:Aplastic anemia|aplastic anemia]]. A significant amount of radium's danger comes from its daughter radon: Being a gas, it can enter the body far more readily than can its parent radium.<ref name=epa/>

{{As of|2015}}, <sup>226</sup>Ra is considered to be the most toxic of the quantity radioelements, and it must be handled in tight glove boxes with significant airstream circulation that is then treated to avoid escape of its daughter <sup>222</sup>Rn to the environment. Old ampoules containing radium solutions must be opened with care because radiolytic decomposition of water can produce an overpressure of hydrogen and oxygen gas.<ref name="Ullmann97">
<br/>
{{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
 | pages=97–98
}}
</ref>
The world's largest concentration of <sup>226</sup>Ra is stored within the [[Physics:Lake Ontario Ordnance Works#Interim waste containment structure|Interim Waste Containment Structure]], approximately {{convert|9.6|mi|km|abbr=on}} north of Niagara Falls, New York.<ref>{{cite journal | last = Jenks | first = Andrew | date = July 2002 | title = Model City USA: The Environmental Cost of Victory in World War&nbsp;II and the Cold War | url = https://www.researchgate.net/publication/249292863 | journal = Environmental History | volume = 12 | issue = 77 | pages = 552–577| doi = 10.1093/envhis/12.3.552 }} {{subscription required}}</ref> The Maximum Contaminant Level (MCL) for radium is 5pCi/L for drinking water, however, the OSHA does not set an exposure limit, as there is a radiation limit already set up.<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>

==See also==
{{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)
}}

==Notes==
{{notelist}}

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

==Bibliography==

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

* {{cite book
 |author=Stwertka, Albert
 |year=1998
 |title=Guide to the Elements |edition=revised 
 |publisher=Oxford University Press
 |isbn=978-0-19-508083-4
}}
* {{cite news
 |author=Grady, Denise 
 |date=6 October 1998
 |title=A Glow in the Dark, and a Lesson in Scientific Peril
 |newspaper={{wipe|The New York Times}}
 |access-date=25 December 2007
 |url=https://www.nytimes.com/library/national/science/100698sci-radium.html
}}
* {{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 book
 |author = Clark, Claudia
 |date = 1987
 |title = Radium Girls: Women and industrial health reform, 1910–1935
 |publisher = University of North Carolina Press
 |isbn = 978-0-8078-4640-7
}}
* {{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==

* {{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. [[Organization:National Institutes of Health|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=[[Organization:Washington and Lee University|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=[[Organization:University of Nottingham|University of Nottingham]]
 |url=http://www.periodicvideos.com/videos/088.htm
}}

{{Periodic table (navbox)}}
[[Category:Radium| ]]
[[Category:Chemical elements]]
[[Category:Alkaline earth metals]]

{{Sourceattribution|Radium}}