Radon (Rn)
noble-gasGas
Peso atômico padrão
[222]Configuração eletrônica
[Xe] 6s2 4f14 5d10 6p6Ponto de fusão
-71,15 °CPonto de ebulição
-61,7 °CDensidade
9,73 kg/m³Estados de oxidação
0, +2, +6Eletronegatividade (Pauling)
N/DEnergia de ionização (1ª)
10,7485 eVAno da descoberta
1900Raio atômico
N/DDetalhes
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.
Imagens
Propriedades
Física
- Raio covalente
- 150 pm Comparar Raio covalente de todos os elementos →
- Raio de van der Waals
- 220 pm Comparar Raio de van der Waals de todos os elementos →
- Densidade
- 9,73 kg/m³ Comparar Densidade de todos os elementos →
- Fase nas CNTP
- Gás Comparar Fase nas CNTP de todos os elementos →
- Ponto de fusão
- -71,15 °C Comparar Ponto de fusão de todos os elementos →
- Ponto de ebulição
- -61,7 °C Comparar Ponto de ebulição de todos os elementos →
- Condutividade térmica
- 0,004 W/(m·K) Comparar Condutividade térmica de todos os elementos →
- Capacidade calorífica específica
- 0,094 J/(g·K) Comparar Capacidade calorífica específica de todos os elementos →
- Capacidade calorífica molar
- 20,786 J/(mol·K) Comparar Capacidade calorífica molar de todos os elementos →
- Estrutura cristalina
- Cúbica de faces centradas Comparar Estrutura cristalina de todos os elementos →
Química
- Eletronegatividade (Allen)
- 2,6
- Afinidade eletrônica
- -0,7 eV (valor negativo — prevê-se que o átomo não capte um eletrão adicional)
- Energia de ionização (1ª)
- 10,7485 eV Comparar Energia de ionização (1ª) de todos os elementos →
- Energia de ionização (2ª)
- 18,990065 eV Comparar Energia de ionização (2ª) de todos os elementos →
- Energia de ionização (3ª)
- 29,400101 eV Comparar Energia de ionização (3ª) de todos os elementos →
- Energia de ionização (4ª)
- 36,900127 eV Comparar Energia de ionização (4ª) de todos os elementos →
- Energia de ionização (5ª)
- 52,900182 eV Comparar Energia de ionização (5ª) de todos os elementos →
- Estados de oxidação
- 0, +2, +6 Comparar Estados de oxidação de todos os elementos →
- Elétrons de valência
- 8 Comparar Elétrons de valência de todos os elementos →
- Configuração eletrônica
- [Xe] 6s2 4f14 5d10 6p6
Termodinâmica
- Ponto triplo (temperatura)
- -71 °C
- Ponto triplo (pressão)
- 5,1e+4 Pa
- Ponto crítico (temperatura)
- 104 °C
- Ponto crítico (pressão)
- 6,28e+6 Pa
- Calor de fusão
- 0,03109292 eV Comparar Calor de fusão de todos os elementos →
- Calor de vaporização
- 0,16582889 eV Comparar Calor de vaporização de todos os elementos →
- Calor de atomização
- 0 eV
Nuclear
- Prótons
- 86 Comparar Prótons de todos os elementos →
- Nêutrons
- 136 Comparar Nêutrons de todos os elementos →
- Isótopos conhecidos
- 39 Comparar Isótopos conhecidos de todos os elementos →
- Isótopos estáveis
- 0 Comparar Isótopos estáveis de todos os elementos →
- Número de massa (mais estável)
- 222
- Isótopo mais estável
- Rn-222
- Ano da descoberta
- 1900
Abundância
- Abundância (crosta terrestre)
- 4e-13 mg/kg Comparar Abundância (crosta terrestre) de todos os elementos →
- Abundância (oceano)
- 6 × 10−16 mg/L Comparar Abundância (oceano) de todos os elementos →
Estrutura cristalina
N/D
Estrutura eletrônica
- Elétrons por camada
- 2, 8, 18, 32, 18, 8 Comparar Elétrons por camada de todos os elementos →
Identificadores
- Número CAS
- 10043-92-2 Comparar Número CAS de todos os elementos →
- Símbolo de termo
- 1S0
- InChI
- InChI=1S/Rn
- Chave InChI
- SYUHGPGVQRZVTB-UHFFFAOYSA-N
Configuração eletrônica Medido
Rn: 4f¹⁴ 5d¹⁰ 6s² 6p⁶[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁶Modelo atômico
Os isótopos alteram o número de nêutrons, a massa e a estabilidade — não a configuração eletrônica de um átomo neutro.
Modelo atômico esquemático, sem escala.
Assinatura atômica
Espectro de emissão / absorção
Distribuição isotópica
Sem isótopos estáveis.
| Número de massa | Massa atômica (u) | Abundância natural | Meia-vida |
|---|---|---|---|
| 194 Radioativo | 194,006144 ± 0,000018 | N/D | 780 us |
| 217 Radioativo | 217,003928 ± 0,0000045 | N/D | 593 us |
| 199 Radioativo | 198,99839 ± 0,000068 | N/D | 590 ms |
| 214 Radioativo | 213,995363 ± 0,0000099 | N/D | 259 ns |
| 205 Radioativo | 204,991719 ± 0,000054 | N/D | 170 segundos |
Fase / Estado
Motivo: 86,7 °C acima do ponto de ebulição (-61,7 °C)
Esquemático, sem escala
Pontos de transição de fase
Energias de transição
Energia necessária para fundir 1 mol no ponto de fusão
Energia necessária para vaporizar 1 mol no ponto de ebulição
Densidade
Em condições padrão
Estimada pela lei dos gases ideais à T atual
Avançado
Espectros atômicos
Mostrando 10 de 86. Ordenado por carga do íon (ordem crescente).
Dados de linhas disponíveis ?
| Íon | Carga | Total de linhas | Probabilidades de transição | Designações dos níveis |
|---|---|---|---|---|
| Rn I | 0 | 67 | 0 | 10 |
Dados de níveis disponíveis ?
| Íon | Carga | Níveis |
|---|---|---|
| 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 |
Dados de estrutura cristalina indisponíveis para a fase sólida
Estrutura cristalina: fcc
Compostos
Isótopos (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.
| Número de massa | Massa atômica (u) | Abundância natural | Meia-vida | Modo de decaimento | |
|---|---|---|---|---|---|
| 194 Radioativo | 194,006144 ± 0,000018 | N/D | 780 us | α ≈100%β+ ? | |
| 217 Radioativo | 217,003928 ± 0,0000045 | N/D | 593 us | α =100% | |
| 199 Radioativo | 198,99839 ± 0,000068 | N/D | 590 ms | α ≈100%β+ ? | |
| 214 Radioativo | 213,995363 ± 0,0000099 | N/D | 259 ns | α =100% | |
| 205 Radioativo | 204,991719 ± 0,000054 | N/D | 170 segundos | β+ =75.4±0.9%α =24.6±0.9% |
Propriedades ampliadas
Raios covalentes (dados ampliados)
- Raio covalente (Pyykkö)
- 142 pm
- Raio covalente (Pyykkö, ligação dupla)
- 145 pm
- Raio covalente (Pyykkö, ligação tripla)
- 133 pm
Raios de van der Waals
- Truhlar
- 220 pm
- Alvarez
- 240 pm
- UFF
- 476,5 pm
- MM3
- 243 pm
Raios atômicos e metálicos
- Raio atômico (Rahm)
- 243 pm
Escalas de numeração
- Mendeleev
- 117
- Pettifor
- 6
- Glawe
- 6
Escalas de eletronegatividade
- Ghosh
- 0
- Gunnarsson–Lundqvist
- 4
- Robles–Bartolotti
- 4
Polarizabilidade e dispersão
- Polarizabilidade dipolar
- 35 a.u.
- Polarizabilidade dipolar (incerteza)
- 2 a.u.
- C₆ (Gould–Bučko)
- 408 Ha·Bohr6
Propriedades dos gases nobres
| HALOGENS | RnF2 |
Transições de fase e alótropos
| Ponto de fusão | 202,15 K |
| Ponto de ebulição | 211,45 K |
| Ponto crítico (temperatura) | 377,15 K |
| Ponto crítico (pressão) | 6,28 MPa |
Categorias de estados de oxidação
Dados de referência avançados
Constantes de blindagem (15)
| n | Orbital | 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 |
Modos de decaimento dos isótopos (59)
| Isótopo | Modo | Intensidade |
|---|---|---|
| 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+ | — |
Fatores de espalhamento de raios X (516)
| Energia (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 |
Dados adicionais
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
4×10-13 milligrams per kilogram
Referências (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
6×10-16 milligrams per liter
Referências (1)
Referências
(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.
Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of 17 national laboratories funded by the U.S. Department of Energy. The lab's primary mission is to conduct basic research of the atom's nucleus using the lab's unique particle accelerator, known as the Continuous Electron Beam Accelerator Facility (CEBAF). For more information visit https://www.jlab.org/
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.