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Radon,  86Rn
General properties
Name, symbol Radon, Rn
Appearance Colorless gas
Radon in the periodic table


Atomic number 86
Standard atomic weight (Ar) 222
Group, block 18 (noble gases); p-block
Period period 6
Electron configuration [Xe] 4f14 5d10 6s2 6p6
per shell
2, 8, 18, 32, 18, 8
Physical properties
Phase Gas
Melting point 202 K ​(−71 °C, ​−96 °F)
Boiling point 211.5 K ​(−61.7 °C, ​−79.1 °F)
Density at  (0 °C and 101.325 kPa) 9.73 g/L
when liquid, at  4.4 g/cm3
Triple point 377 K, ​6.28 kPa
Heat of fusion 3.247 kJ/mol
Heat of 18.10 kJ/mol
Molar heat capacity 5R/2 = 20.786 J/(mol·K)
Atomic properties
Oxidation states 0, +2, +6
Electronegativity Pauling scale: 2.2
energies 1st: 1037 kJ/mol
Covalent radius 150 pm
Van der Waals radius 220 pm
Crystal structure
Thermal conductivity 3.61×10−3 W/(m·K)
Magnetic ordering Non-magnetic
CAS Registry Number 10043-92-2
Discovery Ernest Rutherford and Robert B. Owen (1899)
First isolation William Ramsay and Robert Whytlaw-Gray (1910)
· references

Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas. Radon occurs naturally in minute quantities as the immediate decay product of radium, which in turn is an intermediate step in the normal radioactive decay chains through which thorium and uranium slowly decay into various short-lived radioactive elements and finally into lead.



It is inert to most common chemical reactions, such as combustion, because the outer valence shell contains eight electrons. This produces a stable, minimum energy configuration in which the outer electrons are tightly bound.

Radon can be oxidized by powerful oxidizing agents such as fluorine, thus forming radon difluoride (RnF2). It decomposes back to its elements at a temperature of above 250 °C, and it hydrolyzes in contact with water to radon gas and hydrogen fluoride.

An oxide of radon, radon trioxide (RnO3) has been confirmed.

Due to the short half-life of radon, its chemistry hasn't been thoroughly studied.


Radon is a radioactive, colorless, odorless, tasteless noble gas. Due to its short half-life, a concentrated amount of radon may glow on its own because of the intense radiation it produces. If condensed, it becomes phosphorescent yellow, deepening to glowing red as it is chilled below its freezing point.

At standard temperature and pressure, it forms a monatomic gas with a density of 9.73 kg/m3, about 8 times the density of the Earth's atmosphere at sea level. It is sparingly soluble in water, but more soluble than lighter noble gases. It is appreciably more soluble in organic liquids than in water.


Radon can be extracted from natural uranium ores.


To isolate significant amounts of radon, one would need a large amount of uranium or thorium ore. In areas with large geological deposits, the air from the basement of the buildings is constantly pumped out to prevent a dangerous build-up of radon gas. In theory, one could obtain small amounts of radon gas from this process, albeit due to its short half-life, it must be used quickly.

Vials containing large concentrations of radium metal or radium compounds will release radon gas.


  • Study radioactivity
  • Element collecting (placing a piece of natural uranium ore near a radon detector is a convenient setup)



Radon is radioactive and exposure may increase the risk of cancer, specifically lung cancer. People who live in areas where radon is present due to geology, are at a more significant risk of developing lung illnesses. The basement of houses in such areas need to be constantly vented to prevent a dangerous build-up of radon gas.


Radon cannot and should not be stored.


Should be vented in the atmosphere, where it will slowly decay into less harmful products.


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