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| Atomic symbol: Ra |
| Atomic number: 88 |
| Atomic weight: 226.0254 |
| Atomic volume: 45.20 cm3/mol |
| Density: 5 g/cm3 |
| Period Number: 7 |
| Group number: 2 |
| Group name: Alkali Earth |
| Element classification: Metal |
| Phase at room temperature: Solid |
| Melting Point: 973.2 K |
| Boiling point: 1973 K |
| Heat of fusion: ? |
| Heat of vaporization: ? |
| Ionization Energy: 5.279 eV |
| 1st ionization energy: 509.4 kJ/mole |
| 2nd ionization energy: 979.1 kJ/mole |
| 3rd ionization energy: kJ/mole |
| Electronegativity: 0.9 |
| Electron affinity: kJ/mole |
| Specific heat: 0.12 J/gK |
| Heat atomization: 159 kJ/mole atoms |
| Shells: 2,8,18,32,18,8,2 |
| Electron Shell Configuration: [Rn] 7s2 |
| Minimum oxidation number: 0 |
| Maximum oxidation number: 2 |
| Minimum common oxidation number: 0 |
| Maximum common oxidation no: 2 |
Appearance & Characteristics |
| Structure:: bcc: body-centered cubic |
| Color: white |
| Hardness: mohs |
| Toxicity: ? |
| Characteristics: Radioactive, luminescent |
| Uses: neutron source |
| Reaction with air: vigorous, =>RaO2, Ra3N2 |
| Reaction with 6M HCl: ? |
| Reaction with 15M HNO3: ? |
| Reaction with 6M NaOH: ? |
| Number of isotopes: 4 |
| Oxide(s): ? |
| Hydride(s): ? |
| Chloride(s): RaCl2 |
| Atomic Radius: pm |
| Ionic radius (1- ion): pm |
| Ionic radius (1+ ion): pm |
| Ionic radius (2- ion): pm |
| Ionic radius (2+ ion): 162 pm |
| Ionic radius (3+ ion): pm |
| Thermal conductivity: 18.6 J/m-sec-deg |
| Electrical conductivity: 1/mohm-cm |
| Polarizability: 38.3 A^3 |
| Source: pitchblende(U-238 decay) |
| Relative abundance solar system: log |
| Abundance earth's crust: -6 log |
| Estimated crustal abundance: 9×10-7 milligrams per kilogram |
| Estimated oceanic abundance: 8.9×10-11 milligrams per liter |
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| (L. radius: ray) Radium was discovered in 1898 by Mme. Curie in the pitchblende or uraninite of North Bohemia, where it occurs. There is about 1 g of radium in 7 tons of pitchblende. The element was isolated in 1911 by Mme. Curie and Debierne by the electrolysis of a solution of pure radium chloride employing a mercury cathode; on distillation in an atmosphere of hydrogen, this amalgam yielded the pure metal. |
| Originally, radium was obtained from the rich pitchblende ore found in Joachimsthal, Bohemia. The carnotite sands of Colorado furnish some radium, but richer ores are found in the Republic of Zaire and the Great Lake region of Canada. Radium is present in all uranium minerals, and could be extracted, if desired, from the extensive wastes of uranium processing. Large uranium deposits are located in Ontario, New Mexico, Utah, Australia, and elsewhere. |
| Radium is obtained commercially as bromide and chloride; it is doubtful if any appreciable stock of the isolated element now exists. The pure metal is brilliant white when freshly prepared, but blackens on exposure to air, probably due to formation of the nitride. It exhibits luminescence, as do its slats; it decomposes in water and is somewhat more volatile than barium. It is a member of the alkaline-earth group of metals. Radium imparts a carmine red color to a flame. Radium emits alpha, beta, and gamma rays and when mixed with beryllium produce neutrons. One gram of 226Ra undergoes 3.7 x 1010 disintegrations per second. The curie is defined as that amount of radioactivity which has the same disintegration rate as 1 g of 226Ra. Twenty five isotopes are now known; radium 226, the common isotope, has a half-life of 1600 years. |
| One gram of radium produces about 0.0001 ml (stp) of emanation, or radon gas, per day. This is purged from the radium and sealed in minute tubes, which are used in the treatment of cancer and other diseases. Radium was used in the producing of self-luminous paints, neutron sources, and in medicine for the treatment of disease. Other radioisotopes, such as 60Co, are now being used in place of radium. Some of these sources are much more powerful, and others are safer to use. Radium loses about 1% of its activity in 25 years, being transformed into elements of lower atomic weight. Lead is a final product of disintegration. Stored radium and radium-containing products or minerals should be ventilated to prevent build-up of radon. |
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