|silvery white metallic|
|Name, symbol, number||radium, Ra, 88|
|Element category||alkaline earth metal|
|Group, period, block||2, 7, s|
|Standard atomic weight||(226) g·mol−1|
|Electron configuration||[Rn] 7s2|
|Electrons per shell||2, 8, 18, 32, 18, 8, 2 (Image)|
|Density (near r.t.)||5.5 g·cm−3|
|Melting point||973 K, 700 °C, 1292 °F|
|Boiling point||2010 K, 1737 °C, 3159 °F|
|Heat of fusion||8.5 kJ·mol−1|
|Heat of vaporization||113 kJ·mol−1|
|Oxidation states||2 (strongly basic oxide)|
|Electronegativity||0.9 (Pauling scale)|
|Ionization energies||1st: 509.3 kJ·mol−1|
|2nd: 979.0 kJ·mol−1|
|Covalent radius||221±2 pm|
|Van der Waals radius||283 pm|
|Crystal structure||body-centered cubic|
|Electrical resistivity||(20 °C) 1 µΩ·m|
|Thermal conductivity||(300 K) 18.6 W·m−1·K−1|
|CAS registry number||7440-14-4|
|Most stable isotopes|
|Main article: Isotopes of radium|
Radium (pronounced /ˈreɪdiəm/, RAY-dee-əm) is a radioactive chemical element which has the symbol Ra and atomic number 88. Its appearance is almost pure white, but it readily oxidizes on exposure to air, turning black. Radium is an alkaline earth metal that is found in trace amounts in uranium ores. It is extremely radioactive. Its most stable isotope, 226Ra, has a half-life of 1602 years and decays into radon gas.
The heaviest of the alkaline earth metals, radium is intensely radioactive and resembles barium in its chemical behavior. This metal is found in tiny quantities in the uranium ore pitchblende, and various other uranium minerals. Radium preparations are remarkable for maintaining themselves at a higher temperature than their surroundings, and for their radiations, which are of three kinds: alpha particles, beta particles, and gamma rays.
When freshly prepared, pure radium metal is brilliant white, but blackens when exposed to air (probably due to nitride formation). Radium is luminescent (giving a faint blue color), reacts violently with water and oil to form radium hydroxide and is slightly more volatile than barium. The normal phase of radium is a solid.
Some of the few practical uses of radium are derived from its radioactive properties. More recently discovered radioisotopes, such as 60Co and 137Cs, 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.
Radium was formerly used in self-luminous paints for watches, nuclear panels, aircraft switches, clocks, and instrument dials. In the mid-1920s, a lawsuit was filed by five dying "Radium Girl" dial painters who had painted radium-based luminous paints on the dials of watches and clocks. The dial painters' exposure to radium caused serious health effects which included sores, anemia and bone cancer. This is because radium is treated as calcium by the body, and deposited in the bones, where radioactivity degrades marrow and can mutate bone cells.
The young, low-income, women dial painters had been (explicitly) encouraged to used their lips to shape the paintbrush, and (implicitly) encouraged to play with this "harmless glow-in-the-dark" paint by painting their fingernails, teeth, etc. More than 100 former watch dial painters ultimately died.
During the litigation, it was determined that company scientists and management had taken considerable precautions to protect themselves from the effects of radiation, yet had not seen fit to protect their employees. Worse, for several years, the companies had attempted to cover up the effects and avoid liability by insisting that the Radium Girls were instead suffering from syphilis. This complete disregard for employee welfare had a significant impact on the formulation of occupational disease labor law.
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 shaped paint brushes by lip. Radium was still used in dials as late as the 1960s, but there were no further injuries to dial painters. This further highlighted that the plight of the Radium Girls was completely preventable.
After the 1960s, radium paint was first replaced with promethium paint, and later by tritium bottles which continue to be used today. Although the beta radiation from tritium is potentially dangerous if ingested, it has replaced radium in these applications.
Radium was also put in some foods for taste and as a preservative, but also exposed many people to radiation. Radium was once an additive in products like toothpaste, hair creams, and even food items due to its supposed curative powers. Such products soon fell out of vogue and were prohibited by authorities in many countries, after it was discovered they could have serious adverse health effects. (See for instance Radithor.) 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 early 1970s.
In 1909, the famous Rutherford experiment used radium as an alpha source to probe the atomic structure of gold. This experiment led to the Rutherford model of the atom and revolutionised the field of nuclear physics.
Radium (usually in the form of radium chloride) was used in medicine to produce radon gas which in turn is used as a cancer treatment, for example several of these radon sources were used in Canada in the 1920s and 1930s. The isotope 223Ra is currently under investigation for use in medicine as cancer treatment of bone metastasis.
Radium (Latin radius, ray) was discovered by Marie Skłodowska-Curie and her husband Pierre in 1898 in pitchblende coming from North Bohemia, in the Czech Republic (area around Jáchymov). While studying pitchblende the Curies removed uranium from it and found that the remaining material was still radioactive. They then separated out a radioactive mixture consisting mostly of barium which gave a brilliant green flame color and crimson carmine spectral lines which had never been documented before. The Curies announced their discovery to the French Academy of Sciences on 26 December 1898.
In 1910, radium was isolated as a pure metal by Curie and André-Louis Debierne through the electrolysis of a pure radium chloride solution by using a mercury cathode and distilling in an atmosphere of hydrogen gas.
Radium 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. UMHK offered to Marie Curie her first gramme of radium.
Historically the decay products of radium were known as radium A, B, C, etc. These are now known to be isotopes of other elements as follows:
On February 4, 1936 radium E became the first radioactive element to be made synthetically in the US. Dr. John Jacob Livingood at the radiation lab at University of California, Berkeley was bombarding several elements with 5-MEV deuterons. He noted that irradiated bismuth emits fast electrons with a 5-day half-life ... the behavior of Radium E. 
Radium is a decay product of uranium and is therefore found in all uranium-bearing ores. (One ton of pitchblende typically yields about one seventh of a gram of radium). Radium was originally acquired from pitchblende ore from Joachimsthal, Bohemia, in the Czech Republic. Carnotite sands in Colorado provide some of the element, but richer ores are found in the Democratic Republic of the Congo and the Great Lakes area of Canada, and can also be extracted from uranium processing waste. Large radium-containing uranium deposits are located in Canada (Ontario), the United States (New Mexico, Utah, and Virginia), Australia, and in other places.
Its compounds color flames crimson carmine (rich red or crimson color with a shade of purple) and give a characteristic spectrum. Due to its geologically short half life and intense radioactivity, radium compounds are quite rare, occurring almost exclusively in uranium ores.
Radium (Ra) has 25 different known isotopes, four of which are found in nature, with 226Ra being the most common. 223Ra, 224Ra, 226Ra and 228Ra are all generated naturally in the decay of either Uranium (U) or Thorium (Th). 226Ra is a product of 238U decay, and is the longest-lived isotope of radium with a half-life of 1602 years; next longest is 228Ra, a product of 232Th breakdown, with a half-life of 5.75 years.
Radium is over one million times more radioactive than the same mass of uranium. Its decay occurs in at least seven stages; the successive main products have been studied and were called radium emanation or exradio (now identified as radon), radium A (polonium), radium B (lead), radium C (bismuth), etc. Radon is a heavy gas and the later products are solids. These products are themselves radioactive elements, each with an atomic weight a little lower than its predecessor.
Radium loses about 1% of its activity in 25 years, being transformed into elements of lower atomic weight with lead being the final product of disintegration.
The SI unit of radioactivity is the becquerel (Bq), equal to one disintegration per second. The Curie is a non-SI unit defined as that amount of radioactivity which has the same disintegration rate as 1 gram of Ra-226 (3.7 x 1010 disintegrations per second, or 37 GBq).
Handling of radium has been blamed for Marie Curie's premature death.
RADIUM (from Lat. radius, ray), a metallic chemical element obtained from pitchblende, a uranium mineral, by P. and Mme. Curie and G. Bemont in 1898; it was so named on account of the intensity of the radioactive emanations which it yielded. Its discovery was a sequel to H. Becquerel's observation in 1896 that certain uranium preparations emitted a radiation resembling the X rays observed by Röntgen in 1895. Like the X rays, the Becquerel rays are invisible; they both traverse thin sheets of glass or metal, and cannot be refracted; moreover, they both ionize gases, i.e. they discharge a charged electroscope, the latter, however, much more feebly than the former. Characteristic, also, is their action on a photographic plate, and the phosphorescence which they occasion when they impinge on zinc sulphide and some other salts. Notwithstanding, these resemblances, these two sets of rays are not indentical. Mme. Curie, regarding radioactivity - i.e. the emission of rays like those just mentioned - as a property of some undiscovered substance, submitted pitchblende to a most careful analysis. After removing the uranium, it was found that the bismuth separated with a very active substance - polonium; this element was afterwards isolated by Marckwald, and proved to be identical with his radiotellurium; that the barium could be separated with another active substance - radium; whilst a third fraction, composed mainly of the rare earths (thorium, &c.), yielded to Debierne another radioactive element - actinium, which proved to be identical with the emanium of Giesel. Another radioactive substance - ionium - was isolated from carnotite, a uranium mineral, by B. B. Boltwood in 1905. Radioactive properties have also been ascribed to other elements, e.g. thorium and lead. There is more radium than any other radioactive element, but its excessive rarity may be gauged by the facts that Mme. Curie obtained only a fraction of a gramme of the chloride and Giesel 2 to 3 gramme of the bromide from a ton of uranium residues.
There is a mass of evidence to show that radium is to be regarded as an element, and in general its properties resemble those of the metals of the alkaline earths, more particularly barium. To the bunsen flame a radium salt imparts an intense carmine-red colour (barium gives a green). The spectrum, also, is very characteristic. The atomic weight, 226.4, places the element in a vacant position in group II. of the periodic classification, along with the alkaline earth metals.
Generally speaking, the radiation is not simple. Radium itself emits three types of rays: (1) the a rays, which are regarded as positively charged helium atoms; these rays are stopped by a single sheet of paper; (2) the s rays, which are identified with the cathode rays, i.e. as a single electron charged negatively; these rays can penetrate sheets of aluminium, glass, &c., several millimetres thick; and (3) the 'y rays - which are non-electrified radiations characterized by a high penetrating power, i % surviving after traversing 7 cm. of lead or 150 cm. of water. In addition, radium evolves an "emanation" which is an extraordinarily inert gas, recalling the "inactive" gases of the atmosphere. We thus see that radium is continually losing matter and energy as electricity; it is also losing energy as heat, for, as was observed by Curie and Laborde, the temperature of a radium salt is always a degree or two above that of the atmosphere, and they estimated that a gramme of pure radium would emit about 100 gramme-calories per hour.
The Becquerel rays have a marked chemical action on certain substances. The Curies showed that oxygen was convertible into ozone, and Sudborough that yellow phosphorus gave the red modification when submitted to their influence. More interesting are the observations of D. Berthelot, F. Bordas, C. Doelter and others, that the rays induce important changes in the colours of many minerals. (See Radioactivity.) The action of radium on human tissues was unknown until 1901, when, Professor Becquerel of Paris having incautiously carried a tube in his waistcoat pocket, there appeared on the skin within fourteen days a severe inflammation which was known as the famous "Becquerel burn." Since that time active investigation into the action of radium on diseased tissues has been carried on, resulting in the establishment in Paris in 1906 of the "Laboratoire biologique du Radium." Similar centres for study have been inaugurated in other countries, notably one in London in 1909. The diseases to which the application has been hitherto confined are papillomata, lupus vulgaris, epithelial tumours, syphilitic ulcers, pigmentary naevi, angiomata, and pruritus and chronic itching of the skin; but the use of radium in therapeutics is still experimental. The different varieties of rays used are controlled by the intervention of screens or filtering substances, such as silver, lead or aluminium. Radium is analgesic and bactericidal in its action.
See Radiumtherapie, by Wickham and Degrais (1909); Die therapeutische Wirkung der Radiumstrahlen, by O. Lassar, in Report of Radiology Congress, Brussels, 1906; E. Dorn, E. Baumann and S. Valentiner in Physische Zeitung (1905); Abbe in Medical Record (October 1907).
Radium is a chemical element on the periodic table. It was discovered by Marie Curie. Its symbol is Ra. The word "symbol" is confusing as it is not a picture but an abbreviation-a short version of a word.
It's used in several things, like Luminous Watches, which are now banned.