|
General |
Name, Symbol, Number | Radon, Rn, 86 |
Chemical series | Noble gases |
Group, Period, Block | 18 (VIIIA), 6 , p |
Density, Hardness | 9.73 kg/m3 (273 K), NA |
Appearance | colorless |
Atomic Properties |
Atomic weight | [222] amu |
Atomic radius (calc.) | no data (120) pm |
Covalent radius | 145 pm |
van der Waals radius | no data |
Electron configuration | [Xe]4f14 5d10 6s2 6p6 |
e- 's per energy level | 2, 8, 18, 32, 18, 8 |
Oxidation states (Oxide) | 0 (unknown) |
Crystal structure | Cubic face centered |
Physical Properties |
State of matter | gas (nonmagnetic) |
Melting point | 202 K (-96 °F) |
Boiling point | 211.3 K (-79.1 °F) |
Molar volume | 50.50 ×10-3 m3/mol |
Heat of vaporization | 16.4 kJ/mol |
Heat of fusion | 2.89 kJ/mol |
Vapor pressure | NA |
Speed of sound | NA |
Miscellaneous |
Electronegativity | no data |
Specific heat capacity | 94 J/(kg*K) |
Electrical conductivity | no data |
Thermal conductivity | 0.00364 W/(m*K) |
1st ionization potential | 1037 kJ/mol |
Most Stable Isotopes |
|
SI units & STP are used except where noted. |
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.
Essentially 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 is 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.
Radon 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 rabid 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.
Radon (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.
On average, one molecule of radon is in 1 x 10
21 molecules of air. Every
square mile of
soil down to depth of 6
inches has about 1
gram of radium, which decays to radon and release tiny amounts of this deadly gas into the atmosphere. Radon can be found in some
spring waters[?] and
hot springs.
There 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.
Radon is a carcinogenic gas.
Radon 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 which can easily enter the airways and become permanently stuck in
lung tissue. 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.