Radon - Rn

General Information


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,


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.

Biological Role

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.

General Information

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.

  Physical Information    
  Atomic Number   86
  Relative Atomic Mass (12C=12.000)   222 (radioactive)
  Melting Point/K   202
  Boiling Point/K   211.4
  Density/kg m-3   9.73 (gas, 273K)
  Ground State Electron Configuration   [Xe]4f145d106s26p6
  Electron Affinity(M-M-)/kJ mol-1   -41

  Key Isotopes          
  nuclide 219Rn 220Rn 222Rn    
  atomic mass 219.01 220.01 222.02    
  natural abundance trace trace trace    
  half-life 4 secs 55 secs 3.82 days    

Other Information  
Enthalpy of Fusion/kJ mol-1 2.7
Enthalpy of Vaporisation/kJ mol-1 18.1
Oxidation States  
Covalent Bonds /kJ mol-1  
not applicable    
  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+