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| Radium |
Today, The Grandma has been resting after the Christmas dinner. She has decided to read a little about two important scientists who she admires a lot, Marie and Pierre Curie.
The Curies announced their discovery to the French Academy of Sciences on a day like today in 1898. Before reading about The Curies, The Grandma has studied a new lesson of her Elementary Language Practice manual (Grammar 54 & Checkpoint 9).
The Curies announced their discovery to the French Academy of Sciences on a day like today in 1898. Before reading about The Curies, The Grandma has studied a new lesson of her Elementary Language Practice manual (Grammar 54 & Checkpoint 9).
More information: Pronouns 2
Radium is a chemical element with symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen, rather than oxygen, on exposure to air, forming a black surface layer of radium nitride (Ra3N2). All isotopes of radium are highly radioactive, with the most stable isotope being radium-226, which has a half-life of 1600 years and decays into radon gas, specifically the isotope radon-222. When radium decays, ionizing radiation is a product, which can excite fluorescent chemicals and cause radioluminescence.
Radium, in the form of radium chloride, was discovered by Marie and Pierre Curie in 1898. 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 metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1911.
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| Pierre Curie |
In nature, radium is found in uranium and, to a lesser extent, 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 adverse health effects are likely when it is incorporated into biochemical processes because of its radioactivity and chemical reactivity.
Currently, other than its use in nuclear medicine, radium has no commercial applications; formerly, it was used as a radioactive source for radioluminescent devices and also in radioactive quackery for its supposed curative powers. Today, these former applications are no longer in vogue because radium's toxicity has since become known, and less dangerous isotopes are used instead in radioluminescent devices.
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 barium.
More information: American Physical Society
Pure radium is a volatile silvery-white metal, although its lighter congeners calcium, strontium, and barium have a slight yellow tint. Its color rapidly vanishes in air, yielding a black layer of radium nitride (Ra3N2). Its melting point is either 700 °C or 960 °C and its boiling point is 1,737 °C. Both of these values are slightly lower than those of barium, confirming periodic trends down the group 2 elements. Like barium and the alkali metals, radium crystallizes in the body-centered cubic structure at standard temperature and pressure: the radium–radium bond distance is 514.8 picometers.
Radium has a density of 5.5 g/cm3, higher than that of barium, again confirming periodic trends; the radium-barium density ratio is comparable to the radium-barium atomic mass ratio, due to the two elements' similar crystal structures.
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| Marie Curie |
Radium was discovered by Marie Sklodowska-Curie and her husband Pierre Curie on 21 December 1898, in a uraninite, pitchblende, sample. While studying the mineral earlier, the Curies removed uranium from it and found that the remaining material was still radioactive.
They separated out an element similar to bismuth from pitchblende in July 1898, which turned out to be polonium. They then separated out a radioactive mixture consisting mostly of two components: compounds of barium, which gave a brilliant green flame color, and unknown radioactive compounds which gave carmine spectral lines that had never been documented before.
The Curies found the radioactive compounds to be very similar to the barium compounds, except that they were more insoluble. This made it possible for the Curies to separate out 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. 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.
More information: Nobel Prize
On September 1910, Marie Curie and André-Louis Debierne announced that they had isolated radium as a pure metal through the electrolysis of a pure radium chloride (RaCl2) solution using a mercury cathode, producing a radium–mercury amalgam. This amalgam was then heated in an atmosphere of hydrogen gas to remove the mercury, leaving pure radium metal. Later that same year, E. Eoler isolated radium by thermal decomposition of its azide, Ra(N3)2.
Radium metal was first industrially produced in the beginning of the 20th century by Biraco, a subsidiary company of Union Minière du Haut Katanga (UMHK) in its Olen plant in Belgium.
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| Pierre & Marie Curie |
The common historical unit for radioactivity, the curie, is based on the radioactivity of 226Ra.
Some of the few practical uses of radium are derived from its radioactive properties. More recently discovered radioisotopes, 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.
The isotope 223Ra, under the trade name Xofigo, was approved by the United States Food and Drug Administration in 2013 for use in medicine as a cancer treatment of bone metastasis. 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. 225Ra 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.
More information: Factinate
Radium is still used today as a radiation source in some industrial radiography devices to check for flawed metallic parts, similarly to X-ray imaging. When mixed with beryllium, radium acts as a neutron source.
Radium-beryllium neutron sources are still sometimes used even today, but other materials such as polonium are now more common: about 1500 polonium-beryllium neutron sources, with an individual activity of 1,850 Ci (68 TBq), have been used annually in Russia. These RaBeF4-based (α, n) neutron sources have been deprecated despite the high number of neutrons they emit, 1.84×106 neutrons per second, in favour of 241Am–Be sources. Today, the isotope 226Ra is mainly used to form 227Ac by neutron irradiation in a nuclear reactor.
When radium was discovered, no one knew that it would prove
useful in hospitals. The work was one of pure science.
And this is a proof that scientific work must not be
considered from the point of view of the direct usefulness of it.
Marie Curie
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