Radon (Rn)
noble-gasGas
Masse atomique relative standard
[222]Configuration électronique
[Xe] 6s2 4f14 5d10 6p6Point de fusion
-71,15 °CPoint d’ébullition
-61,7 °CMasse volumique
9,73 kg/m³États d’oxydation
0, +2, +6Électronégativité (Pauling)
N/DÉnergie d’ionisation (1re)
10,7485 eVAnnée de découverte
1900Rayon atomique
N/DDétails
Radon is a radioactive noble gas and the heaviest naturally occurring member of group 18. It is chemically inert compared with most elements, but its radioactivity makes it environmentally and medically important. Natural radon is produced mainly in uranium and thorium decay chains, especially as ²²²Rn from radium-226. Its gaseous form lets it migrate from rocks, soils, and building materials into air and enclosed spaces.
Radon is present in the atomosphere at very low concentrations. See Wikipedia for discussion of concentration. At ordinary temperatures radon is a colorless gas; when cooled below the freezing point, radon exhibits a brilliant phosphorescence which becomes yellow as the temperature is lowered and orange-red at the temperature of liquid air. It has been reported that fluorine reacts with radon, forming a fluoride. Radon clathrates have also been reported.
Radon was discovered by Friedrich Ernst Dorn, a German chemist, in 1900 while studying radium's decay chain. Originally named niton after the Latin word for shining, nitens, radon has been known as radon since 1923. Today, radon is still primarily obtained through the decay of radium. At normal room temperatures, radon is a colorless, odorless, radioactive gas. The most common forms of radon decay through alpha decay. Alpha decay usually isn't considered to be a great radiological hazard since the alpha particles produced by the decay are easily stopped. However, since radon is a gas, it is easily inhaled and living tissue is directly exposed to the radiation. Although it has a relatively short half-life, radon decays into longer lived, solid, radioactive elements which can collect on dust particles and be inhaled as well. For these reasons, there is some concern as to the amount of radon present within homes. Radon seeps into houses as a result of the decay of radium, thorium or uranium ores underground and varies greatly from location to location. On average, the earth's atmosphere is 0.0000000000000000001% radon.
When cooled to its solid state, radon glows yellow. The glow becomes orange-red as the temperature is lowered.
Radon's most stable isotope, radon-222, has a half-life of about 3.8 days. It decays into polonium-218 through alpha decay.
The name was derived from radium; called niton at first, from the Latin word nitens meaning shining.The element was discovered in 1900 by Dorn, who called it radium emanation. In 1908 Ramsay and Gray, who named it niton, isolated the element and determined its density, finding it to be the heaviest known gas. It is essentially inert and occupies the last place in the zero group of gases in the Periodic Table. Since 1923, it has been called radon.
Pure radon is a colorless, odorless, monatomic gas at ordinary temperature and pressure. It can be condensed at low temperature to a liquid and then a solid, but macroscopic handling is limited by intense radioactivity and radiolytic effects.
Radon has no broad commercial use. Historically, sealed radon sources were used in some radiotherapy practices before safer and more controllable radionuclides became preferred. It has also been used as a tracer in hydrology, geology, and atmospheric studies because it is continuously generated in rocks and has isotope-dependent decay times. Present use is mainly analytical or research-related, including calibration and environmental measurement work.
Small amounts of radon are sometimes used by hospitals to treat some forms of cancer. Radon fluoride (RnF) is the only confirmed compound of radon.
Radon is still produced for therapeutic use by a few hospitals by pumping it from a radium source and sealing it in minute tubes, called seeds or needles, for application to patient. This practice has been largely discontinued as hospitals can get the seeds directly from suppliers, who make up the seeds with the desired activity for the day of use.
Isotopes in Earth/Planetary Science
Both 220Rn and 222Rn (with half-lives of 56 s and 3.8 days, respectively) are used to study underground environmental and atmospheric gaseous-transport processes [568] United States Geological Survey. Resources on Isotopes-Periodic Table-Radon, U.S. Geological Survey (2014), Feb. 25; http://wwwrcamnl.wr.usgs.gov/isoig/period/rn_iig.html., [569] State of California Department of Conservation. Indoor Radon, State of California Department of Conservation (2017), April 8; http://www.consrv.ca.gov/CGS/minerals/hazardous_minerals/radon/Pages/index.aspx., [570] L. S. Quindos Poncela, C. Sainz Fernandez, I. Fuente Merino, J. L. Gutierrez Villanueva, A. Gonzalez Diez. Acta Geophysica.61, 848 (2013).. The interaction of radon with streams and rivers enables it to be used as a tracer in groundwater studies (Fig. IUPAC.86.1). 222Rn has a short residence time in streams and river channels, which leads to radon loss. As a result, if an area of a stream or river has a high concentration of radon, it suggests that there are local groundwater inputs [568] United States Geological Survey. Resources on Isotopes-Periodic Table-Radon, U.S. Geological Survey (2014), Feb. 25; http://wwwrcamnl.wr.usgs.gov/isoig/period/rn_iig.html., [569] State of California Department of Conservation. Indoor Radon, State of California Department of Conservation (2017), April 8; http://www.consrv.ca.gov/CGS/minerals/hazardous_minerals/radon/Pages/index.aspx., [570] L. S. Quindos Poncela, C. Sainz Fernandez, I. Fuente Merino, J. L. Gutierrez Villanueva, A. Gonzalez Diez. Acta Geophysica.61, 848 (2013).. In a deep (100 m) contaminated aquifer at a refinery site in Mexico, where the contaminated source was too deep to be directly accessible for sampling, Schubert et al. [571] M. Schubert, M. Balcazar, A. Lopez, P. Peña, J. H. Flores, K. Knöller. Isot. Environ. Health Stud.43, 215 (2007). collected groundwater samples from a few wells available at the site. They used the partitioning of the natural tracer 222Rn between uncontaminated groundwater and the NAPL (non-aqueous phase-liquid, such as oil, gasoline, and petroleum) source zone, and they were able to approximately identify the location of the NAPL source zone. As noted in Section 4.88.1, 222Rn has been used to quantify submarine groundwater discharge [572] R. N. Peterson, W. C. Burnett, M. Taniguchi, J. Chen, I. R. Santos, T. Ishitobi. J. Geophys. Res.113, C09021 (2008)..
Isotopes in Geochronology
222Rn has been used as a tool to date groundwater in combination with other isotopes or elemental ratios (i.e. helium/radon and xenon/radon amount ratios) [568] United States Geological Survey. Resources on Isotopes-Periodic Table-Radon, U.S. Geological Survey (2014), Feb. 25; http://wwwrcamnl.wr.usgs.gov/isoig/period/rn_iig.html., [574] T. F. Kraemer, D. P. Genereux. “Applications of uranium- and thorium-series radionuclides in catchment hydrology studies”, in Isotope Tracers in Catchment Hydrology, C. Kendall, J. J. McDonnell (Eds.), Elsevier, Amsterdam (1998)..
Radon is the least chemically studied noble gas because its isotopes are radioactive and available only in small amounts. The most established chemistry involves strong oxidizing and fluorinating conditions, with radon difluoride (RnF₂) reported as a radon compound. Ionic or complex fluoride species have been inferred in matrix and tracer experiments, but many details remain uncertain. Oxidation states above 0 are possible in principle, yet radon chemistry is much less developed than xenon chemistry.
See more information at the Radon compound page.
Radon is hazardous chiefly because inhaled radioactive decay products can lodge in the respiratory tract and irradiate tissue with alpha particles. The risk depends strongly on isotope, concentration, ventilation, exposure time, and the behavior of short-lived progeny such as polonium isotopes. Radon is also an asphyxiant like other gases if present at very high concentrations, but radiation exposure is the practical concern.
Care must be taken in handling radon, as with other radioactive materials. The main hazard is from inhalation of the element and its solid daughters which are collected on dust in the air. Good ventilation should be provided where radium, thorium, or actinium is stored to prevent build-up of the element. Radon build-up is a health consideration in uranium mines. Recently radon build-up in homes has been a concern. Many deaths from lung cancer are caused by radon exposure. In the U.S. it is recommended that remedial action be taken if the air in homes exceeds 4 pCi/l.
Radon forms naturally where uranium or thorium decay occurs in minerals and soils. Being a gas, it can diffuse through pore spaces, dissolve to some extent in groundwater, and enter buildings through cracks or service penetrations. Outdoors it is usually diluted rapidly, while enclosed or poorly ventilated spaces can accumulate higher concentrations. Its decay products attach to aerosols and surfaces, changing their mobility and exposure pathways.
Radon is not traded as a normal industrial commodity. It is generated continuously by decay of radium in sealed sources or collected in small quantities for specialized calibration and research needs. Supply is constrained less by elemental scarcity than by radiological controls, isotope half-lives, and the limited demand for handling the gas. Most practical applications that once used radon have been replaced by other radionuclides, electronic instruments, or direct environmental monitoring methods.
Formed from the decay of radium in the earths crust.
Radon has no stable isotopes, so it cannot accumulate over geological or cosmic timescales. In nature it appears only as a transient daughter in decay chains of long-lived heavy nuclides such as uranium and thorium. In extraterrestrial materials, any radon would likewise be short-lived and locally produced rather than primordial.
- Radon is the densest noble gas encountered naturally on Earth.
- The isotope ²²²Rn has a half-life of about 3.8 days, long enough for migration through soil.
- Radon was once called niton, a name reflected in the old symbol Nt.
- Indoor radon levels often vary with season, pressure differences, and building ventilation.
- Radon measurements can reveal subsurface gas movement and some groundwater interactions.
Images
Propriétés
Propriétés physiques
- Rayon covalent
- 150 pm Comparer : Rayon covalent de tous les éléments →
- Rayon de van der Waals
- 220 pm Comparer : Rayon de van der Waals de tous les éléments →
- Masse volumique
- 9,73 kg/m³ Comparer : Masse volumique de tous les éléments →
- Phase aux CNTP
- Gaz Comparer : Phase aux CNTP de tous les éléments →
- Point de fusion
- -71,15 °C Comparer : Point de fusion de tous les éléments →
- Point d’ébullition
- -61,7 °C Comparer : Point d’ébullition de tous les éléments →
- Conductivité thermique
- 0,004 W/(m·K) Comparer : Conductivité thermique de tous les éléments →
- Capacité thermique massique
- 0,094 J/(g·K) Comparer : Capacité thermique massique de tous les éléments →
- Capacité thermique molaire
- 20,786 J/(mol·K) Comparer : Capacité thermique molaire de tous les éléments →
- Structure cristalline
- Cubique à faces centrées Comparer : Structure cristalline de tous les éléments →
Propriétés chimiques
- Électronégativité (Allen)
- 2,6
- Affinité électronique
- -0,7 eV (valeur négative — l'atome ne devrait pas lier d'électron supplémentaire)
- Énergie d’ionisation (1re)
- 10,7485 eV Comparer : Énergie d’ionisation (1re) de tous les éléments →
- Énergie d’ionisation (2e)
- 18,990065 eV Comparer : Énergie d’ionisation (2e) de tous les éléments →
- Énergie d’ionisation (3e)
- 29,400101 eV Comparer : Énergie d’ionisation (3e) de tous les éléments →
- Énergie d’ionisation (4e)
- 36,900127 eV Comparer : Énergie d’ionisation (4e) de tous les éléments →
- Énergie d’ionisation (5e)
- 52,900182 eV Comparer : Énergie d’ionisation (5e) de tous les éléments →
- États d’oxydation
- 0, +2, +6 Comparer : États d’oxydation de tous les éléments →
- Électrons de valence
- 8 Comparer : Électrons de valence de tous les éléments →
- Configuration électronique
- [Xe] 6s2 4f14 5d10 6p6
Propriétés thermodynamiques
- Point triple (température)
- -71 °C
- Point triple (pression)
- 5,1e+4 Pa
- Point critique (température)
- 104 °C
- Point critique (pression)
- 6,28e+6 Pa
- Enthalpie de fusion
- 0,03109292 eV Comparer : Enthalpie de fusion de tous les éléments →
- Enthalpie de vaporisation
- 0,16582889 eV Comparer : Enthalpie de vaporisation de tous les éléments →
- Enthalpie d’atomisation
- 0 eV
Propriétés nucléaires
- Protons
- 86 Comparer : Protons de tous les éléments →
- Neutrons
- 136 Comparer : Neutrons de tous les éléments →
- Isotopes connus
- 39 Comparer : Isotopes connus de tous les éléments →
- Isotopes stables
- 0 Comparer : Isotopes stables de tous les éléments →
- Nombre de masse (isotope le plus stable)
- 222
- Isotope le plus stable
- Rn-222
- Année de découverte
- 1900
Abondance
- Abondance (croûte terrestre)
- 4e-13 mg/kg Comparer : Abondance (croûte terrestre) de tous les éléments →
- Abondance (océan)
- 6 × 10−16 mg/L Comparer : Abondance (océan) de tous les éléments →
Structure cristalline
N/D
Structure électronique
- Électrons par couche
- 2, 8, 18, 32, 18, 8 Comparer : Électrons par couche de tous les éléments →
Identifiants
- Numéro CAS
- 10043-92-2 Comparer : Numéro CAS de tous les éléments →
- Symbole de terme
- 1S0
- InChI
- InChI=1S/Rn
- Clé InChI
- SYUHGPGVQRZVTB-UHFFFAOYSA-N
Configuration électronique Mesuré
Rn: 4f¹⁴ 5d¹⁰ 6s² 6p⁶[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁶Modèle atomique
Les isotopes diffèrent par leur nombre de neutrons, leur masse et leur stabilité — pas par la configuration électronique de l’atome neutre.
Modèle atomique schématique, non à l’échelle.
Empreinte atomique
Spectre d’émission / d’absorption
Distribution isotopique
Aucun isotope stable.
| Nombre de masse | Masse atomique (u) | Abondance naturelle | Demi-vie |
|---|---|---|---|
| 194 Radioactif | 194,006144 ± 0,000018 | N/D | 780 us |
| 217 Radioactif | 217,003928 ± 0,0000045 | N/D | 593 us |
| 199 Radioactif | 198,99839 ± 0,000068 | N/D | 590 ms |
| 214 Radioactif | 213,995363 ± 0,0000099 | N/D | 259 ns |
| 205 Radioactif | 204,991719 ± 0,000054 | N/D | 170 secondes |
Phase / État
Explication: 86,7 °C au-dessus du point d’ébullition (-61,7 °C)
Schématique, non à l’échelle
Points de transition de phase
Énergies de transition
Énergie nécessaire pour faire fondre 1 mol au point de fusion
Énergie nécessaire pour vaporiser 1 mol au point d’ébullition
Masse volumique
Dans les conditions standard
Estimée par la loi des gaz parfaits à la température actuelle
Données avancées
Spectres atomiques
Affichage de 10 sur 86. Tri par charge ionique croissante.
Raies répertoriées ?
| Ion | Charge | Nombre total de raies | Probabilités de transition | Désignations des niveaux |
|---|---|---|---|---|
| Rn I | 0 | 67 | 0 | 10 |
Niveaux répertoriés ?
| Ion | Charge | Niveaux |
|---|---|---|
| Rn I | 0 | 127 |
| Rn II | +1 | 3 |
| Rn III | +2 | 2 |
| Rn IV | +3 | 2 |
| Rn V | +4 | 2 |
| Rn VI | +5 | 2 |
| Rn VII | +6 | 2 |
| Rn VIII | +7 | 2 |
| Rn IX | +8 | 2 |
| Rn X | +9 | 2 |
Données de structure cristalline indisponibles pour la phase solide
Structure cristalline: fcc
Composés
Isotopes (5)
Thirty-nine isotopes are known. Radon-222 is the most common. It has a half-life of 3.823 days and is an alpha emitter. It is estimated that every square mile of soil to a depth of 6 inches contains about 1 g of radium, which releases radon in tiny amounts into the atmosphere. Radon gas can collect in buildings, creating a health risk. The Environmental Protection Agency estimates that responsible for an estimated 20,000 lung cancer deaths each year. More on radon and health. Radon is present in some spring waters, such as those at Hot Springs, Arkansas.
| Nombre de masse | Masse atomique (u) | Abondance naturelle | Demi-vie | Mode de désintégration | |
|---|---|---|---|---|---|
| 194 Radioactif | 194,006144 ± 0,000018 | N/D | 780 us | α ≈100%β+ ? | |
| 217 Radioactif | 217,003928 ± 0,0000045 | N/D | 593 us | α =100% | |
| 199 Radioactif | 198,99839 ± 0,000068 | N/D | 590 ms | α ≈100%β+ ? | |
| 214 Radioactif | 213,995363 ± 0,0000099 | N/D | 259 ns | α =100% | |
| 205 Radioactif | 204,991719 ± 0,000054 | N/D | 170 secondes | β+ =75.4±0.9%α =24.6±0.9% |
Propriétés étendues
Rayons covalents (données étendues)
- Rayon covalent (Pyykkö)
- 142 pm
- Rayon covalent (Pyykkö, liaison double)
- 145 pm
- Rayon covalent (Pyykkö, liaison triple)
- 133 pm
Rayons de van der Waals
- Truhlar
- 220 pm
- Alvarez
- 240 pm
- UFF
- 476,5 pm
- MM3
- 243 pm
Rayons atomiques et métalliques
- Rayon atomique (Rahm)
- 243 pm
Échelles de numérotation
- Mendeleev
- 117
- Pettifor
- 6
- Glawe
- 6
Échelles d’électronégativité
- Ghosh
- 0
- Gunnarsson–Lundqvist
- 4
- Robles–Bartolotti
- 4
Polarisabilité et dispersion
- Polarisabilité dipolaire
- 35 a.u.
- Polarisabilité dipolaire (incertitude)
- 2 a.u.
- C₆ (Gould–Bučko)
- 408 Ha·Bohr6
Propriétés des gaz nobles
| HALOGENS | RnF2 |
Transitions de phase et allotropes
| Point de fusion | 202,15 K |
| Point d’ébullition | 211,45 K |
| Point critique (température) | 377,15 K |
| Point critique (pression) | 6,28 MPa |
Catégories d’états d’oxydation
Données de référence avancées
Constantes d’écran (15)
| n | Orbitale | σ |
|---|---|---|
| 1 | s | 1,6659 |
| 2 | p | 4,562 |
| 2 | s | 22,5864 |
| 3 | d | 13,4027 |
| 3 | p | 23,7194 |
| 3 | s | 24,9149 |
| 4 | d | 38,0572 |
| 4 | f | 37,6688 |
| 4 | p | 36,6988 |
| 4 | s | 35,85 |
Modes de désintégration des isotopes (59)
| Isotope | Mode | Intensité |
|---|---|---|
| 193 | A | 100% |
| 194 | A | 100% |
| 194 | B+ | — |
| 195 | A | 100% |
| 196 | A | 100% |
| 196 | B+ | — |
| 197 | A | 100% |
| 197 | B+ | — |
| 198 | A | 93% |
| 198 | B+ | — |
Facteurs de diffusion des rayons X (516)
| Énergie (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 2,83964 |
| 10,1617 | — | 3,21791 |
| 10,3261 | — | 3,64656 |
| 10,4931 | — | 4,05083 |
| 10,6628 | — | 4,4288 |
| 10,8353 | — | 4,83437 |
| 11,0106 | — | 5,24445 |
| 11,1886 | — | 5,68932 |
| 11,3696 | — | 6,15277 |
| 11,5535 | — | 6,62072 |
Données complémentaires
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
4×10-13 milligrams per kilogram
Références (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
6×10-16 milligrams per liter
Références (1)
Références
(9)
Data deposited in or computed by PubChem
The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.
Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.
The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.
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The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.
The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database
This section provides all form of data related to element Radon.
The element property data was retrieved from publications.