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Element Fact
In 1961, the International Union of Pure and Applied Chemistry adopted the isotope carbon-12 as the basis of atomic weight, which has a mass of exactly 12.000 atomic mass unit.

Radon, Rn

radon sample

Atomic number: 86
Atomic mass: [222] (no stable nuclide)
Natural abundance: 10-15 ppm (in air)
211Rn (210.990585) - *%
222Rn (222.017570) - *%

History and Production

The name is derived from radium. It was discovered in 1900 by F.E. Dorn who called it radium emanation. It was first isolated and studied in 1902 by E. Rutherford and F. Soddy. In 1908, W. Ramsey has also isolated the element and named it niton. He had determined the density and found it to be the heaviest known gas. Other names has also been called, depending on which radioactive series it originates in. Since 1923, it has been called radon. It is used in the treatment of cancer and as a radioactive source in testing metal castings.

Physical Data

It is a colorless gas. When frozen, it exhibits a phosphorescence which becomes yellow as the temperature is lowered. Radon is present in minute amount (1 part of radon in 1 x 1021 part of air) in the atmosphere due to the decay of natural radium. Recently, radon is a health concern since its release from soils can easily trapped indoors. Inhaling radon has result in deaths from lung cancer due to the radioactive a emmission.

Interatomic distance: -
Melting point: -71C
Boiling point: -61.7C
Thermal conductivity/Wm-1K-1: 0.00364 (27C)
Density/kgm-3: 4400 (m.p.), 9.73 (0C)

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: -
Gibbs free energy of formation: -
Entropy: 176.2 J/mol K
Heat capacity: 20.8 J/mol K

Electronic data

Electronic configuration: [Xe] 4f14 5d10 6s2 6p6 = [Rn]
Term symbol: 1S0
Electron affinity: (not stable)   Electronegativity (Pauline): -
Ionization energy (first, second, third): 1037.07,- , - kJ/mol

Chemical properties

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