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Name , symbol , atomic number Radium, Ra, 88
Element category Alkaline earth metals
Group , period , block 2 , 7 , p
Appearance silvery-white-metallic
CAS number 7440-14-4
EC number 231-122-4
ECHA InfoCard 100.028.293
Mass fraction of the earth's envelope 9.5 · 10 −11  ppm
Atomic mass 226.0254 u
Atomic radius 215 pm
Covalent radius 221 pm
Van der Waals radius 283 pm
Electron configuration [ Rn ] 7 s 2
1. Ionization energy 5.278 423 9 (25) eV 509.29 kJ / mol
2. Ionization energy 10.14718 (6) eV979.05 kJ / mol
3. Ionization energy 31.0 (1.6) eV2 990 kJ / mol
4. Ionization energy 41.0 (1.7 eV)3 960 kJ / mol
5. Ionization energy 52.9 (1.9) eV5 100 kJ / mol
Physical state firmly
Crystal structure body-centered cubic
density 5.5 g / cm³ (20 ° C )
Melting point 973 K (700 ° C)
boiling point 2010 (1737 ° C)
Molar volume 41.09 · 10 −6 m 3 · mol −1
Heat of evaporation 125 kJ / mol
Heat of fusion 8 kJ mol −1
Electric conductivity 1 · 10 6 A · V −1 · m −1
Thermal conductivity 19 W m −1 K −1
Oxidation states 2
Normal potential −2.916 V (Ra 2+ + 2e - → Ra)
Electronegativity 0.9 ( Pauling scale )
isotope NH t 1/2 ZA ZE (M eV ) ZP
223 ra −1% 11.435 d α 5.979 219 para
224 ra −1% 3.66 d α 5.789 220 para
225 ra {syn.} 14.9 d β - 0.357 225 Ac
226 Ra 100  % 1602 a α 4,871 222 para
227 ra −1% 42.2 min β - 1.325 227 Ac
228 ra −1% 5.7 a β - 0.046 228 Ac
For other isotopes see list of isotopes
Hazard and safety information
GHS hazard labeling
no classification available
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions .

Radium ( Latin radius 'ray', because of its radioactivity , like radon ) is a chemical element with the element symbol Ra and the atomic number 88. In the periodic table it is in the 2nd main group , or the 2nd  IUPAC group and counts with it to the alkaline earth metals .


The luminous dots on the numbers and on the hands of this watch contain radium

Radium was discovered in France on December 21, 1898 by the Polish physicist Marie Curie and her husband, the French physicist Pierre Curie , in the pitchblende from the Bohemian St. Joachimsthal . The finding that purified uranium (as a metal salt) only showed a small fraction of the radioactivity of the original uranium ore was a pioneering finding. Instead, most of the radioactivity of the ore was found in the barium sulfate precipitate. For the separated element, the pronounced radiation properties were then used to give the name.

Radium is dangerous to humans

Radium fountain in Bad Elster (1924)
Cosmetics containing radium (around 1925)

Radium compounds were initially considered to be relatively harmless or even beneficial to health and were advertised in the United States and Europe as a drug for a variety of ailments (e.g. as an anti-cancer agent) or processed as an additive in products that glow in the dark. The processing took place without any protective measures. Cosmetics and luxury foods containing radium were advertised until the mid-1930s.

After the establishment of the Sankt Joachimsthal radium bath in Bohemia in 1906, immediately before the First World War, the radium baths in Germany flourished due to the presumed healing effects of radium. While Bad Kreuznach already advertised itself as the strongest radium brine bath before the war , after the war - besides St. Joachimsthal and Oberschlema - it was above all Bad Brambach . The latter two places claimed to be the strongest radium or radium mineral bath in the world, whereby it should be noted that in the healing springs mainly radon , whereas radium only occurred in small traces. Correctly, these baths should have been called radon baths .

In the 1920s, the harmful effects of radium were recognized when many of the dial painters known as Radium Girls in orange (New Jersey) developed cancerous tumors on the tongue and lips due to the ionizing radiation of the self-luminous dial paint , because they brushed their mouths with their brushes sharpened. New York dentist Theodore Blum in 1924 published an article about the disease of radium jaw (Engl. Radium jaw ). He initially attributed the disease to the toxicity of phosphorus . It was Harrison Martland , a pathologist in New Jersey , who finally began a study in 1925, the result of which was correctly attributed to radium.

Until 1931, radium-infused water called radithor was sold in small bottles for drinking. At the latest with the death of the steel magnate Eben Byers in 1932, who had consumed two bottles of Radithor a day from 1928 to 1930 , it was undisputedly clear that radium can cause severe health damage.


Radium is one of the rarest natural elements; its share in the earth's crust is about 7 · 10 −12  %. It is in a natural decay equilibrium with uranium. This means that the radium content of the rock in question is proportional to its uranium content (provided that transport processes do not take place). The mass-related factor is about 1 / 3,000,000 (approx. 0.3 g / t heavy metal). In the radioactive decay to which it is subject, it is the mother nuclide of radon -222.


As a metal , it is a typical alkaline earth element . It's soft and shiny silver. Radium is very similar to the lighter group homologue barium , but even less noble than this. In contact with oxygen it oxidizes very quickly and reacts violently with water .

In aqueous solution it is always positively bivalent. The divalent cation is colorless. Like barium, it forms some sparingly soluble salts , such as carbonate , sulfate and chromate . Other salts such as the halides (the fluoride is only sparingly soluble), nitrate and acetate are easily soluble. The salts give the Bunsen flame a crimson color.


The mass numbers of its isotopes range from 202 to 234, their half-lives are between about 182 nanoseconds for 216 Ra and 1602 years for 226 Ra. Since the radium isotope 226 Ra can be obtained in weighable quantities, it is possible to study its chemical properties quite well.


Radium in radio-oncology

The use of closed radium capsules was an early form of brachytherapy for cancers, e.g. B. the cervix. 2013, pharmaceutical manufacturers brought Bayer HealthCare with radium-223 dichloride (Xofigo®) a radiopharmaceutical based on 223 Ra, an alpha emitter with a half-life of 11.43 days, for intravenous application in symptomatic bone metastases of castration-resistant prostate cancer on the market.

Radium in physics class

Radium preparations are available to represent alpha radiation and can be used in cloud chambers while observing the safety regulations . There are two intensities (3.7 k Bq and 60 kBq) are available.

Environmental issues

Radium and uranium mining

Since radium is coupled to uranium via the decay equilibrium, it inevitably accompanies it in its ores and is also circulated during mining activities, i.e. released from the geological enclosure. In ore processing, essentially only the uranium is of interest ( yellow cake ); the radium is part of the residue fraction and is deposited as overburden. This means that most of the radioactivity of the uranium ore originally mined is not contained in the uranium sold, but in the sludge dumps for ore processing.

The living earth's surface (environment) is influenced on the one hand by the radiation emanating from the radium itself (especially alpha radiation ), on the other hand by its effect as a radon source . Mitigating the effects of this type is the goal of remedial efforts in post-mining landscapes (see also Wismut ).

Radium and metabolic industries

Wherever large quantities of natural, heterogeneously composed mixtures of substances are converted, their trace content of uranium and radium also carries natural radioactivity. This is especially true for coal combustion in power plants (coal deposits as hydrogeological uranium sinks). Dust that has not been retained partially transports the radium of the coal into the atmosphere. In the event of effective flue gas cleaning measures, the radium then also appears in the solid residues, some of which are marketable.


Radium compounds are almost exclusively in the + II oxidation state . These are mostly colorless, salt-like solids that turn yellow over time as a result of radiolysis of their own alpha radiation .

The category: Radium compounds gives an overview of radium compounds .

safety instructions

Classifications according to the CLP regulation are not available because they only include chemical hazard and play a completely subordinate role compared to the hazards based on radioactivity . The latter also only applies if the amount of substance involved is relevant.


  • Under the direction of the German geologist and extraordinary professor for stratigraphy and paleontology Wilhelm Salomon-Calvi , a radium-brine thermal spring in the Heidelberg-Bergheim district with a water temperature of 27 ° C was successfully drilled at a depth of 998 meters on August 14, 1918 . In July 1928 a radium brine bath was opened there. The radium spa operation ended with the beginning of the Second World War. In 1957, the so-called healing spring, which, according to Salomon, was the richest source in the world in radium salts at the time, suddenly dried up . The spring is the only thermal spring in Germany that contains pure radium salt. Drinking cures and baths should help against diseases.
  • A so-called radium cup was found in 2015 at a recycling company in Alsfeld and secured by employees of the Gießen regional council. Such cups with an insert for radium salt were used for drinking at the beginning of the 20th century, because at that time it was assumed that ionizing radiation had a beneficial effect on health.
  • In Wipperfürth there is the company Radium Lampenwerk GmbH, founded in 1904 as a light bulb factory and still producing today, registry court Cologne HRB 37474. The company has been a 100 percent subsidiary of Osram GmbH since 1988 .
  • Compared to other foods, Brazil nuts contain increased levels of radium-224, radium-226 and radium-228. If you eat two Brazil nuts a day (about 8 grams), you get an additional dose of 160 microsieverts / year.


Web links

Wiktionary: Radium  - explanations of meanings, word origins, synonyms, translations
Commons : Radium  - collection of images, videos and audio files

Individual evidence

  1. ^ Harry H. Binder: Lexicon of the chemical elements , S. Hirzel Verlag, Stuttgart 1999, ISBN 3-7776-0736-3 .
  2. The values ​​for the properties (Infobox) are taken from www.webelements.com (Radium) , unless otherwise stated .
  3. Manjeera Mantina, Adam C. Chamberlin, Rosendo Valero, Christopher J. Cramer, Donald G. Truhlar: Consistent van der Waals Radii for the Whole Main Group. In: J. Phys. Chem. A. 2009, 113, pp. 5806-5812, doi: 10.1021 / jp8111556 .
  4. a b c d e Entry on radium in Kramida, A., Ralchenko, Yu., Reader, J. and NIST ASD Team (2019): NIST Atomic Spectra Database (ver. 5.7.1) . Ed .: NIST , Gaithersburg, MD. doi : 10.18434 / T4W30F ( https://physics.nist.gov/asd ). Retrieved June 13, 2020.
  5. a b c d e Entry on radium at WebElements, https://www.webelements.com , accessed on June 13, 2020.
  6. ^ NN Greenwood and A. Earnshaw: Chemistry of the elements. VCH, Weinheim 1988, ISBN 3-527-26169-9 , p. 136.
  7. The hazards emanating from radioactivity do not belong to the properties to be classified according to the GHS labeling. With regard to other hazards, this element has either not yet been classified or a reliable and citable source has not yet been found.
  8. Les "pouvoirs miraculeux" de la radioactivité .
  9. ^ B. Lambert: Radiation: early warnings; late effects. (PDF; 1.8 MB) In: Harremoës, Poul u. a. (Ed.): Late lessons from early warnings: the precautionary principle 1896-2000. Copenhagen: European Environment Agency, 2001, ISBN 92-9167-323-4 , pp. 31-37.
  10. For a detailed description of the dangerousness of radium for humans cf. the presentation of Rowland, RE : Radium in Humans - A Review of US Studies ( Memento of the original from June 9, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 5.5 MB), Argonne (Illinois): Argonne National Laboratory, September 1994, pp. 23-24. @1@ 2Template: Webachiv / IABot / www.ustur.wsu.edu
  11. T. Blum: Osteomyelitis of the Mandible and Maxilla. In: Journal of the American Dental Association . Volume 11, 1924, pp. 802-805, doi: 10.14219 / jada.archive.1924.0111 .
  12. ^ First major publication by the research team: HS Martland: Some Unrecognized Dangers in the Use and Handling of Radioactive Substances. In: Proceedings of the New York Pathological Society. Volume 25, 1925, pp. 88-92, doi: 10.1001 / jama.1925.02670230001001 .
  13. HS Martland and RE Humphries: Osteogenic sarcoma in dial painters using luminous paint. In: Archives of Pathology. Volume 7, 1929, pp. 406-417, doi: 10.3322 / canjclin.23.6.368 (free full text).
  14. G. Audi, O. Bersillon, J. Blachot, AH Wapstra: The NUBASE evaluation of nuclear and decay properties . In: Nuclear Physics A . tape 729 , 2003, p. 114 , doi : 10.1016 / j.nuclphysa.2003.11.001 (English, online ).
  15. European Medicines Agency : Xofigo. Radium-223 dichloride (PDF; 75 kB). EMA / 579264/2013, EMEA / H / C / 002653, November 13, 2013.
  16. ^ Salomon, Wilhelm: The drilling of the Heidelberg Radium-Sol-Therme and their geological conditions . In: Treatises of the Heidelberg Academy of Sciences. Mathematical and natural science class. Berlin 1927, DNB 365061662 , p. 13.
  17. Former Radium brine bath. In: Database building research / restoration. State Office for Monument Preservation Baden-Württemberg, accessed on November 19, 2017 .
  18. 75 years of Heidelberg thermal swimming pool. (PDF; 9.6 MB) (No longer available online.) Stadtwerke Heidelberg, 2014, archived from the original on December 1, 2017 ; Retrieved November 19, 2017 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.swhd.de
  19. Grandma's drinking cup - radiantly beautiful: Radioactively contaminated radium cup found during household liquidation, osthessen-news.de January 15, 2015. Accessed April 29, 2015.
  20. The Chronicle of Radium. In: radium.de . Retrieved April 29, 2015.
  21. Federal Office for Radiation Protection (BfS) - Natural radioactivity in food. In: bfs.de. December 18, 2014, accessed October 25, 2015 .