What is Radon
Radon (pronunciation: RAY-don) is an odorless, radioactive element that belongs to the family of noble gases and is represented by the chemical symbol Rn [1, 2]. It is colorless at room temperatures, but becomes phosphorescent when cooled below its freezing temperature and gradually turns into orange-red when the temperature is further lowered to the boiling point of liquid air .
There are more than 35 radioactive isotopes of radon, ranging from 195Rn-229Rn, out of which 222Rn is the most stable with a half-life period of 3.823 days and forms 218Po through α-decay . It has four naturally occurring isotopes, including 218Rn, 219Rn, 220Rn, and 222Rn .
Where is Radon Found
Radon is always found in nature because it is produced from the radioactive decomposition of radium-226 that is present in phosphate rocks, uranium ores, metamorphic rocks, and common rocks like limestone [1, 3]. A small amount of radon also occurs in the atmosphere .
Origin of its Name: It is named for the radioactive metallic element radium because radon was first identified during the radioactive decay of radium .
Who discovered it: The German physicist Friedrich Ernst Dorn is known for its discovery .
When and How was it Discovered
In 1899, Robert B. Owens and Ernest Rutherford found a radioactive gas emanating from thorium . In that same year, Marie and Pierre Curie detected a gas being released by radium . In 1900, Ernst Dorn discovered a gas while studying the decay chain of radium at the German city of Halle .
We now know that the radioactive gas observed by the Curies and Ernst Dorn was Radon-222 while the gas detected by Rutherford was Radon-220 . In 1908, Robert Whytlaw-Gray and William Ramsay collected enough radon and determined the properties of radon at the University College, London .
|Atomic number||86 |
|CAS number||10043-92-2 |
|Position in the periodic table||Group||Period||Block|
|18 ||6 ||p |
Properties and Characteristics of Radon
|Relative atomic mass|| |
|Atomic mass|| amu |
|Molar mass||210.9906010 ± 0.0000070 g/mol |
|Color||Colorless [1, 7]|
|Melting point/freezing point||-71 °C, -96 °F |
|Boiling point||-61.7 °C, -79.1 °F |
|Density||0.009074 g cm-3 |
|State of matter at room temperature (solid/liquid/gas)||Gas [1, 7]|
|Thermal (heat) conductivity||0.00361 W/(m K) |
|Flammability||Not flammable |
|Specific heat||94 J kg-1 K-1 |
|Bulk modulus||Unknown |
|Shear modulus||Unknown |
|Young’s modulus||Unknown |
|– Temperature (K)||400||600||800||1000||1200||1400||1600||1800||2000||2200||2400|
|– Pressure (Pa)||–||–||–||–||–||–||–||–||–||–||–|
|Oxidation states||2 |
|Isotopes||Isotope||Mass||Abundance (%)||Half-life||Mode of decay|
|211Rn||210.991||–||14.6 h||β+, EC|
Atomic Data of Radon (Element 86)
|Valence electrons||8 |
|– n||6 |
|– ℓ||1 |
|– mℓ||1 |
|– ms||-1/2 |
|Electron configuration (noble gas configuration)||[Xe] 4f145d106s26p6 |
|– Number of electrons||86 |
|– Number of neutrons||136 |
|– Number of protons||86 |
|Radius of Atom|
|– Atomic radius||2.20 Å |
|– Covalent radius||1.46 Å |
|Electronegativity (Pauling-scale)||Unknown |
|Electron affinity||Not stable |
|Ionization energy (kJ mol-1)||1st||2nd||3rd||4th||5th||6th||7th||8th|
What is it Used for
- Radioactive decomposition of radon is useful for obtaining polonium .
- Radon emitted from a radium source can be used in cancer therapy . It was commonly used in hospitals for the treatment of tumors through implantation of minute tubes in which the gas was sealed [1, 7]. Today, it has been replaced by safer treatment options [1, 7].
- Radon testing kits are used for analyzing indoor radon levels in places where large concentrations of radon gas can accumulate indoors . If the test result shows the level is 4 pCi/L or more, mitigation systems are used to reduce radon concentrations .
- Researchers use radon soil-concentration to map subsurface geological faults since concentrations generally increase over the faults . Groundwater radon concentrations are also analyzed for earthquake prediction .
Radon Toxicity and Health Effects
The decay products of radon have been considered as being carcinogenic . Since it can be inhaled, people exposed to high levels of radon are at risk of developing lung cancer . The chances of getting affected by lung cancer are much higher in smokers who are exposed to radon . It is thought to have had played a role in evolution and could be responsible for the background radiation of the Earth which can cause genetic modifications .
- It is the heaviest known chemically inactive gas that can form compounds with other substances only under extreme conditions [3, 4].
- It is graphically represented by an image of the radiation hazard symbol with background images of houses indicating that the gas can accumulate in houses .
The price of radon gas is about $4 per m .