|Radon - Rn
Radon was discovered by F.E. Dorn in 1900 in Halle, Germany, who named it radium emantium. The element was isolated in 1908 by Ramsay and Gray, who named it niton. Since 1923 it has been called radon.
Radon is a colourless, odourless inert gas.
Radon is produced naturally from the decay of a radium isotope, 226Ra.
Radon decays into radioactive polonium and alpha rays, and this emitted radiation makes radon useful in cancer therapy. The gas is sealed in minute tubes called seeds or needles and implanted into the site of a tumour. The diseased tissue is thus destroyed in situ by the radiation.
Radon has no known biological role. It is toxic due to its radioactivity, the main hazard arising from inhalation, as the element and its radioactive daughters collect on dust particles.
Radon is the densest known gas.
Chemically, radon should resemble xenon but it has been little studied because any compounds which are formed are destroyed by hazardous radiation. It is reported that radon reacts with fluorine to give radon fluoride, and radon clathrates have also been reported. At ordinary temperatures radon is a colourless gas, but when cooled below freezing point it exhibits a brilliant phosphorescence which becomes yellow as the temperature is lowered and orange at the temperature of liquid air.
|Relative Atomic Mass (12C=12.000)||222 (radioactive)|
|Density/kg m-3||9.73 (gas, 273K)|
|Ground State Electron Configuration||[Xe]4f145d106s26p6|
|Electron Affinity(M-M-)/kJ mol-1||-41|
|half-life||4 secs||55 secs||3.82 days|
|Enthalpy of Fusion/kJ mol-1||2.7|
|Enthalpy of Vaporisation/kJ mol-1||18.1|
|Covalent Bonds /kJ mol-1|
|Ionisation Energies/kJ mol-1|
|M - M+||1037|
|M+ - M2+|
|M2+ - M3+|
|M3+ - M4+|
|M4+ - M5+|
|M5+ - M6+|
|M6+ - M7+|
|M7+ - M8+|
|M8+ - M9+|
|M9+ - M10+|