Radon (Rn)

Isotopes of Radon

Isotope Atomic Mass Half-life Mode of Decay Nuclear Spin Nuclear Magnetic Moment
Rn-210 209.98968 2.40 hours EC to At-210;
α to Po-206
0 No data available 
Rn-211  210.99059  14.60 hours  EC to At-211;
α to Po-207
1/2 0.60
Rn-212 211.99069 24.00 minutes α to Po-208 0 No data available 
Rn-213 212.99387 0.025 seconds α to Po-209 9/2 No data available 
Rn-214 213.99535 0.000027 seconds α to Po-210 0 -0.020
Rn-215 214.99873 0.0000023 seconds α to Po-211 9/2 No data available 
Rn-216 216.00026 0.000045 seconds α to Po-212 No data available  No data available 
Rn-217 217.00391 0.0006 seconds α to Po-213 9/2 No data available 
Rn-218 218.00559 0.035 seconds α to Po-214 0 No data available 
Rn-219 219.00948 3.96 seconds α to Po-215 5/2 No data available 
Rn-220 220.01138 55.60 seconds α to Po-216 0 No data available 
Rn-221 221.0156 25.00 minutes α to Po-217;
β- to Fr-221
7/2 No data available 
Rn-222 222.017571 3.8235 days α to Po-218 0 No data available 
Rn-223 223.0218 23.2 minutes α to Po-219;
β- to Fr-223
No data available  No data available 
Rn-224 224.0241 107 minutes β- to Fr-224 No data available  No data available 
Rn-225 225.0284 4.50 minutes β- to Fr-225 No data available  No data available 
Rn-226 226.0309 7.40 minutes β- to Fr-226 No data available  No data available 


Radon was discovered in 1900 by Friedrich Ernst Dorn. It was called “niton” until 1923, after the Latin word nitens, meaning “shining.” Since 1923 it has been called “radon,” after the element radium. It is one of the intermediate Uranium-238 series, and the “first daughter” of Radium-226. A colorless gas that is strongly absorbed onto surfaces, it dissolves in water and is slightly soluble in alcohol and other organic solvents. It solidifies to an opaque crystalline solid.

Radon is a radiation source for treating cancer. It is safer than Radium-226 because of its much shorter half-life. In addition, its solution in petroleum jelly is used in some ointments for treating certain skin diseases. Non-medical uses of radon include its application as a gaseous tracer to detect leaks; to measure flow rates; as a source of neutrons in radon-beryllium mixes; to ionize gases to promote radon-induced chemical reactions such as oxidation, decomposition and polymerization; to measure reaction rates; and as a point source of gamma rays in radiography to inspect welding and castings of metals.

Exposure to radon can cause lung cancer. While it is the second most frequent cause of lung cancer, it is the number one cause among non-smokers, according to United States Environmental Protection Agency estimates.

Properties of Radon

Name Radon
Symbol Rn
Atomic number 86
Atomic weight 222
Standard state Gas at 298 °K;(the heaviest known mononuclear gas at 298 °K)
CAS Registry ID 10043-92-2
Group in periodic table 18
Group name Noble gas
Period in periodic table 6
Block in periodic table p-block
Color Colorless
Classification Nonmetallic
Melting point -71 °C
Boiling point -61.7 °C
Liquefication point -61.8 °C
Solidification point -71 ºC
Thermal conductivity 0.00361 W/(m·K)
Heat of vaporization 17 kJ·mol-1
Heat of fusion 3 kJ·mol-1
Density of gas .0093 g/cm3 
Density of solid 4.0 g/cm3
Electron configuration [He]4f145d106s26p6
Oxidation state
Critical temperature 104.4 ºC
Critical pressure 62.4 atm

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