Radon
Category:Chemical elements\n
\n| \n\n |
\n\n| General |
\n\n| Name, Symbol, Number | Radon, Rn, 86 |
\n\n| Chemical series | Noble gases |
\n\n| Group, Period, Block | 18 (VIIIA), 6 , p |
\n\n| Density, Hardness | 9.73 kg/m3 (273 K), NA |
\n\n| Appearance | colorless |
\n\n| Atomic properties |
\n\n| Atomic weight | [222] amu |
\n\n| Atomic radius (calc.) | no data (120) pm |
\n\n| Covalent radius | 145 pm |
\n\n| van der Waals radius | no data |
\n\n| Electron configuration | [Xe]44f14 5d10 6s2 6p6 |
\n\n| e- 's per energy level | 2, 8, 18, 32, 18, 8 |
\n\n| Oxidation states (Oxide) | 0 (unknown) |
\n\n| Crystal structure | Cubic face centered |
\n\n| Physical properties |
\n| State of matter | gas (nonmagnetic) |
\n\n| Melting point | 202 K (-96 °F) |
\n\n| Boiling point | 211.3 K (-79.1 °F) |
\n\n| Molar volume | 50.50 ×1010-6 m3/mol |
\n\n| Heat of vaporization | 16.4 kJ/mol |
\n\n| Heat of fusion | 2.89 kJ/mol |
\n\n| Vapor pressure | NA |
\n\n| Speed of sound | NA |
\n\n| Miscellaneous |
\n\n| Electronegativity | no data |
\n\n| Specific heat capacity | 94 J/(kg*K) |
\n\n| Electrical conductivity | no data |
\n\n| Thermal conductivity | 0.00364 W/(m*K) |
\n\n| 1st ionization potential | 1037 kJ/mol |
\n\n| Most stable isotopes |
\n\n| \n\n |
\n\n| SI units & STP are used except where noted. | \n
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Radon is a
chemical element in the
periodic table that has the symbol
Rn and
atomic number 86. A
radioactive noble gas that is formed by the disintegration of
radium, radon is one of the heaviest gases and is considered to be a health hazard. The most stable
isotope is Rn-222 which has a
half-life of 3.8 days and is used in
radiotherapy.
Notable characteristics
\nEssentially inert, radon is the heaviest noble gas and one of the heaviest gases at room temperature. (The heaviest is tungsten hexafluoride, WF6.) At standard temperature and pressure radon is a colorless gas but when it is cooled below its freezing point it has a brilliant phosphorescence which turns yellow as the temperature is lowered and orange-red at the temperature air liquefies. Some experiments indicate that fluorine can react with radon and form radon fluoride. Radon clathrates have also been reported.
Natural radon concentrations in Earth's atmosphere are so low that natural waters in contact with the atmosphere will continually lose radon by volatilization. Hence, ground water has a higher concentration of Rn-222 than surface water. Likewise, the saturated zone of a soil frequently has a higher radon content than the unsaturated zone due to diffusional losses to the atmosphere.
Applications
\nRadon is sometimes produced by a few hospitals for therapeutic use by pumping its gas from a radium source and storing it in very small tubes which are called seeds or needles. This practice is being phased-out as hospitals get seeds from suppliers who make them with the desired activity levels.
Because of its rapid loss to air, radon is used in hydrologic research that studies the interaction between ground water, streams and rivers. Any significant concentration of radon in a stream or river is a good indicator that there are local inputs of ground water.
History
\nRadon (named for radium) was discovered in 1900 by Friedrich Ernst Dorn, who called it radium emanation. In 1908 William Ramsay and Robert Whytlaw-Gray, who named it niton (Latin nitens meaning "shining"), isolated it, determined its density and that it was the heaviest known gas. It has been called radon since 1923.
Occurrence
\nOn average, there is one molecule of radon in 1 x 1021 molecules of air. Soil down to depth of 6 inches (150 mm) has about 1 gram of radium, which decays to radon and releases tiny amounts of this deadly gas into the atmosphere. Radon can be found in some spring waters and hot springs.
Isotopes
\nThere are twenty known isotopes of radon. The most stable isotope is radon-222 which is a decay product (daughter isotope) of radium-226, has a half-life of 3.823 days and emits radioactive alpha particles. Radon-220 is a natural decay product of thorium and is called thoron. It has a half-life of 55.6 seconds and also emits alpha rays. Radon-219 is derived from actinium, is called actinon, is an alpha emitter and has a half-life of 3.96 seconds.
Precautions
\nRadon is a carcinogenic gas. \nRadon is a radioactive material and must be handled with care at all times. It is hazardous to inhale this element since it emits alpha particles.
Also, its solid decay products, and their respective products, tend to form a fine dust which can easily enter the airways and become permanently stuck in lung tissue, producing heavy localized exposure. Rooms where radium, actinium, or thorium are stored should be well-ventilated in order to prevent build-up in the air. The build-up of radon is a potential health hazard in uranium and some lead mines. Build-up of radon in homes has also been a more recent health concern and many lung cancer cases are attributed to radon exposure each year.
Reference
\n*Los Alamos National Laboratory - Radon
External links
\n*WebElements.com - Radon\n*EnvironmentalChemistry.com - Radon
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