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Radon (Rn)

Radon is a chemical element of the periodic table with chemical symbol Rn and atomic number 86 with an atomic weight of 222 u and is classed as noble gas and is part of group 18 (noble gases). Radon is gas at room temperature.

Radon in the periodic table

Atomic number86
Group18 (Noble gases)
ClassificationNoble Gas
AppearanceColorless gas, occasionally glows green or red in discharge tubes
Color Colorless
Number of protons86 p+
Number of neutrons136 n0
Number of electrons86 e-
From Wikipedia, the free encyclopediaRadon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as a decay product of radium. Its most stable isotope, 222Rn, has a half-life of 3.8 days.

Physical properties

Phase at STPGas
Density9.73 g/cm3
Atomic weight222 u

Thermal properties

Melting point202 K
-71.15 °C
-96.07 °F
Boiling point211.5 K
-61.65 °C
-78.97 °F
Heat of vaporization16.4 kJ/mol

Atomic properties

Electronegativity (Pauling Scale)2.2
Electron affinity-68 kJ/mol
Oxidation states0, +2, +6
Ionization energies
  1. 1037 kJ/mol

Electron configuration for radon

Electron configuration
Shorthand configuration
[Xe] 4f14 5d10 6s2 6p6
Electron configuration
Full configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6
Electron configuration chart
Electrons per shell2, 8, 18, 32, 18, 8
Valence electrons 8
Valency electrons 0
Bohr model
RadonElectron shell for Radon, created by Injosoft ABRn
Figure: Shell diagram of Radon (Rn) atom.
Orbital Diagram

The history of Radon

DiscoveryErnest Rutherford, Robert Bowie Owens (1899)
First isolationWilliam Ramsay, Robert Whytlaw-Gray (1910)
Discovery of radon
Radon was the fifth radioactive element to be discovered, in 1899 by Ernest Rutherford and Robert B. Owens at McGill University in Montreal, after uranium, thorium, radium, and polonium. In 1899, Pierre and Marie Curie observed that the gas emitted by radium remained radioactive for a month. Later that year, Rutherford and Owens noticed variations when trying to measure radiation from thorium oxide. Rutherford noticed that the compounds of thorium continuously emit a radioactive gas that remains radioactive for several minutes, and called this gas "emanation" (from Latin: emanare, to flow out, and emanatio, expiration), and later "thorium emanation" ("Th Em"). In 1900, Friedrich Ernst Dorn reported some experiments in which he noticed that radium compounds emanate a radioactive gas he named "radium emanation" ("Ra Em"). In 1901, Rutherford and Harriet Brooks demonstrated that the emanations are radioactive, but credited the Curies for the discovery of the element. In 1903, similar emanations were observed from actinium by André-Louis Debierne, and were called "actinium emanation" ("Ac Em"). In 1909, Ramsay and Robert Whytlaw-Gray isolated radon and determined its melting temperature and approximate density. In 1910, they determined that it was the heaviest known gas.


List of unique identifiers for Radon in various chemical registry databases
CAS Number10043-92-2
ChemSpider ID23240
EC number233-146-0
PubChem CID Number24857