Radon

Radon, ₈₆Rn

Radon
Pronunciation	/ˈreɪdɒn/ ​(RAY-don)
Appearance	colorless gas
Mass number	[222]
Radon in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Xe ↑ Rn ↓ Og astatine ← radon → francium
Atomic number (Z)	86
Group	group 18 (noble gases)
Period	period 6
Block	p-block
Electron configuration	[Xe] 4f14 5d10 6s2 6p6
Electrons per shell	2, 8, 18, 32, 18, 8
Physical properties
Phase at STP	gas
Melting point	202 K ​(−71 °C, ​−96 °F)
Boiling point	211.5 K ​(−61.7 °C, ​−79.1 °F)
Density (at STP)	9.73 g/L
when liquid (at b.p.)	4.4 g/cm3
Critical point	377 K, 6.28 MPa[1]
Heat of fusion	3.247 kJ/mol
Heat of vaporization	18.10 kJ/mol
Molar heat capacity	5R/2 = 20.786 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 110 121 134 152 176 211
Atomic properties
Oxidation states	common: (none) +2,? +6
Electronegativity	Pauling scale: 2.2
Ionization energies	1st: 1037 kJ/mol
Covalent radius	150 pm
Van der Waals radius	220 pm
Spectral lines of radon
Other properties
Natural occurrence	from decay
Crystal structure	​face-centered cubic (fcc) (predicted)
Thermal conductivity	3.61×10−3  W/(m⋅K)
Magnetic ordering	non-magnetic
CAS Number	10043-92-2
History
Discovery	Ernest Rutherford and Robert B. Owens (1899)
First isolation	William Ramsay and Robert Whytlaw-Gray (1910)
Isotopes of radon v e
Main isotopes[2] Decay abun­dance half-life (t1/2) mode pro­duct 210Rn synth 2.4 h α 206Po 211Rn synth 14.6 h ε 211At α 207Po 222Rn trace 3.8235 d α 218Po 224Rn synth 1.8 h β− 224Fr
Category: Radon view talk edit | references

Radon is a chemical element; it has symbol Rn and atomic number 86. It is a radioactive noble gas and is colorless and odorless. Of the three naturally occurring radon isotopes, only ²²²Rn has a sufficiently long half-life (3.825 days) for it to be released from the soil and rock where it is generated. Radon isotopes are the immediate decay products of radium isotopes. The instability of ²²²Rn, its most stable isotope, makes radon one of the rarest elements. Radon will be present on Earth for several billion more years despite its short half-life, because it is constantly being produced as a step in the decay chains of ²³⁸U and ²³²Th, both of which are abundant radioactive nuclides with half-lives of at least several billion years. The decay of radon produces many other short-lived nuclides, known as "radon daughters", ending at stable isotopes of lead.^{[3] 222}Rn occurs in significant quantities as a step in the normal radioactive decay chain of ²³⁸U, also known as the uranium series, which slowly decays into a variety of radioactive nuclides and eventually decays into stable ²⁰⁶Pb. ²²⁰Rn occurs in minute quantities as an intermediate step in the decay chain of ²³²Th, also known as the thorium series, which eventually decays into stable ²⁰⁸Pb.

Radon was discovered in 1899 by Ernest Rutherford and Robert B. Owens at McGill University in Montreal, and was the fifth radioactive element to be discovered. First known as "emanation", the radioactive gas was identified during experiments with radium, thorium oxide, and actinium by Friedrich Ernst Dorn, Rutherford and Owens, and André-Louis Debierne, respectively, and each element's emanation was considered to a separate substance: radon, thoron, and actinon. Sir William Ramsay and Robert Whytlaw-Gray considered that the radioactive emanations may contain a new element of the noble gas family, and isolated "radium emanation" in 1909 to determine its properties. In 1911, the element Ramsay and Whytlaw-Gray isolated was accepted by the International Commission for Atomic Weights, and in 1923, the International Committee for Chemical Elements and International Union of Pure and Applied Chemistry chose radon as the accepted name for the element's most stable isotope, ²²²Rn.

Under standard conditions, radon is gaseous and can be easily inhaled, posing a health hazard. However, the primary danger comes not from radon itself, but from its decay products, known as radon daughters. These decay products, often existing as single atoms or ions, can attach themselves to airborne dust particles. Although radon is a noble gas and does not adhere to lung tissue (meaning it is often exhaled before decaying), the radon daughters attached to dust are more likely to stick to the lungs. This increases the risk of harm, as the radon daughters can cause damage to lung tissue.^[4] Radon and its daughters are, taken together, often the single largest contributor to an individual's background radiation dose, but due to local differences in geology,^[5] the level of exposure to radon gas differs by location. A common source of environmental radon is uranium-containing minerals in the ground; it therefore accumulates in subterranean areas such as basements. Radon can also occur in ground water, such as spring waters and hot springs.^[6] Radon trapped in permafrost may be released by climate-change-induced thawing of permafrosts,^[7] and radon may also be released into groundwater and the atmosphere following seismic events leading to earthquakes, which has led to its investigation in the field of earthquake prediction.^[8] It is possible to test for radon in buildings, and to use techniques such as sub-slab depressurization for mitigation.^[9][10]

Epidemiological studies have shown a clear association between breathing high concentrations of radon and incidence of lung cancer.^[11] Radon is a contaminant that affects indoor air quality worldwide. According to the United States Environmental Protection Agency (EPA), radon is the second most frequent cause of lung cancer, after cigarette smoking, causing 21,000 lung cancer deaths per year in the United States. About 2,900 of these deaths occur among people who have never smoked. While radon is the second most frequent cause of lung cancer, it is the number one cause among non-smokers, according to EPA policy-oriented estimates.^[12] Significant uncertainties exist for the health effects of low-dose exposures.^[13]