Radium
| General properties | |||||
|---|---|---|---|---|---|
| Name, symbol | Radium, Ra | ||||
| Appearance | Silvery white metallic | ||||
| Radium in the periodic table | |||||
| |||||
| Atomic number | 88 | ||||
| Standard atomic weight (Ar) | 226 | ||||
| Group, block | , s-block | ||||
| Period | period 7 | ||||
| Electron configuration | [Rn] 7s2 | ||||
per shell | 2, 8, 18, 32, 18, 8, 2 | ||||
| Physical properties | |||||
| Silvery white metallic | |||||
| Phase | Solid | ||||
| Melting point | 973 K (700 °C, 1292 °F) | ||||
| Boiling point | 2010 K (1737 °C, 3159 °F) | ||||
| Density near r.t. | 5.5 g/cm3 | ||||
| Heat of fusion | 8.5 kJ/mol | ||||
| Heat of | 113 kJ/mol | ||||
| pressure | |||||
| Atomic properties | |||||
| Oxidation states | +2 | ||||
| Electronegativity | Pauling scale: 0.9 | ||||
| energies |
1st: 509.3 kJ/mol 2nd: 979.0 kJ/mol | ||||
| Covalent radius | 221±2 pm | ||||
| Van der Waals radius | 283 pm | ||||
| Miscellanea | |||||
| Crystal structure | Body-centered cubic (bcc) | ||||
| Thermal conductivity | 18.6 W/(m·K) | ||||
| Electrical resistivity | 1 Ω·m (at 20 °C) | ||||
| CAS Registry Number | 7440-14-4 | ||||
| History | |||||
| Discovery | Pierre and Marie Curie (1898) | ||||
| First isolation | Marie Curie (1910) | ||||
Radium is a chemical element with symbol Ra and atomic number 88. 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.
Contents
Properties
Chemical
Radium metal readily reacts with nitrogen on exposure to air, forming a black surface layer of radium nitride (Ra3N2).
Physical
Radium is a silvery white metal, that quickly tarnishes in air forming a black surface of radium nitride.
Availability
Radium was used in the past in fluorescent paint used for clock and watch indicators, now replaced by the more safe tritium.
Pure radium metal is extremely difficult to get hold of, as it doesn't have common uses and it's very expensive. Likewise, since it's a radioactive material, a permit may be required for it.
In nature, radium is found in uranium ores, most often in pitchblende. One ton of pitchblende typically yields about one seventh of a gram of radium.
Isolation
Radium can be isolated from uranium minerals. Isolation from old radium paint is also possible, but you will need an enormous amount of it, and that amount of radium is unsafe to handle without proper protection.
One student from Austria was able to isolate 0.5 µg of radium in the form of radium carbonate from uranothorianite.[1]
Projects
- Demonstration of fluorescence and radioactivity
- Element collecting
- Source of radon
Handling
Safety
Radium is highly radioactive and its immediate daughter, radon gas, is also radioactive. When ingested, 80% of the ingested radium leaves the body through the feces, while the other 20% goes into the bloodstream, mostly accumulating in the bones. Exposure to radium, internal or external, can cause cancer and other disorders, because radium and radon emit alpha and gamma rays upon their decay, which kill and/or mutate cells.
Storage
Radium must be kept in ampoules at all times to prevent radon gas from being released in closed chambers and to prevent oxidation.
Disposal
Burying it in concrete or in a place with natural deposits of radioactive minerals is a possible choice.
