Global InformationRadon information
| Radon | |||||||||||||||||||||||||||||||||
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| Pronunciation | /ˈreɪdɒn/ | ||||||||||||||||||||||||||||||||
| Appearance | colorless gas | ||||||||||||||||||||||||||||||||
| Mass number | [222] | ||||||||||||||||||||||||||||||||
| Radon in the periodic table | |||||||||||||||||||||||||||||||||
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| 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
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| Atomic properties | |||||||||||||||||||||||||||||||||
| Oxidation states | 0, +2, +6 | ||||||||||||||||||||||||||||||||
| Electronegativity | Pauling scale: 2.2 | ||||||||||||||||||||||||||||||||
| Ionization energies |
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| Covalent radius | 150 pm | ||||||||||||||||||||||||||||||||
| Van der Waals radius | 220 pm | ||||||||||||||||||||||||||||||||
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| 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 | |||||||||||||||||||||||||||||||||
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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 radon-222, 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 radon-222, 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 chain of uranium-238, and that of thorium-232, each of which is an extremely abundant radioactive nuclide with a half-life of several billion years. The decay of radon produces many other short-lived nuclides, known as "radon daughters", ending at stable isotopes of lead.[3] Radon-222 occurs in significant quantities as a step in the normal radioactive decay chain of uranium-238, also known as the uranium series, which slowly decays into a variety of radioactive nuclides and eventually decays into lead-206, which is stable. Radon-220 occurs in minute quantities as an intermediate step in the decay chain of thorium-232, also known as the thorium series, which eventually decays into lead-208, which is stable.
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 from place to place. A common source is uranium-containing minerals in the ground, and therefore it accumulates in subterranean areas such as basements. Radon can also occur in some ground water like spring waters and hot springs.[6] Radon trapped in permafrost may be released by climate change induced thawing of permafrosts.[7] It is possible to test for radon in buildings, and to use techniques such as sub-slab depressurization for mitigation.[8][9]
Epidemiological studies have shown a clear link between breathing high concentrations of radon and incidence of lung cancer. 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.[10] Significant uncertainties exist for the health effects of low-dose exposures.[11]
- ^ Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.122. ISBN 1-4398-5511-0.
- ^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
- ^ Toxicological profile for radon Archived 2016-04-15 at the Wayback Machine, Agency for Toxic Substances and Disease Registry, U.S. Public Health Service, In collaboration with U.S. Environmental Protection Agency, December 1990.
- ^ "Public Health Fact Sheet on Radon — Health and Human Services". Mass.Gov. Archived from the original on 2011-11-21. Retrieved 2011-12-04.
- ^ Kusky, Timothy M. (2003). Geological Hazards: A Sourcebook. Greenwood Press. pp. 236–239. ISBN 9781573564694.
- ^ "Facts about Radon". Facts about. Archived from the original on 2005-02-22. Retrieved 2008-09-07.
- ^ Lamberink, Liny (16 February 2022). "Thawing permafrost can expose northerners to cancer-causing gas, study says". cbc.ca. CBC News. Archived from the original on 17 February 2022. Retrieved 22 February 2024.
- ^ Baraniuk, Chris (11 May 2022). "The race against radon". Knowable Magazine. Annual Reviews. doi:10.1146/knowable-051122-1 (inactive 31 January 2024). Retrieved 17 May 2022.
{{cite journal}}: CS1 maint: DOI inactive as of January 2024 (link) - ^ Poor Legibility
- ^ Cite error: The named reference
epawas invoked but never defined (see the help page). - ^ Dobrzynski, Ludwik; Fornalski, Krzysztof W.; Reszczyńska, Joanna (23 November 2017). "Meta-analysis of thirty-two case–control and two ecological radon studies of lung cancer". Journal of Radiation Research. 59 (2): 149–163. doi:10.1093/jrr/rrx061. PMC 5950923. PMID 29186473.