Selenium (Se)
nonmetalSolid
Masse atomique relative standard
78,971 uConfiguration électronique
[Ar] 4s2 3d10 4p4Point de fusion
220,5 °CPoint d’ébullition
684,85 °CMasse volumique
4809 kg/m³États d’oxydation
−2, −1, 0, +1, +2, +3, +4, +5, +6Électronégativité (Pauling)
2,55Énergie d’ionisation (1re)
9,752368 eVAnnée de découverte
1817Rayon atomique
115 pmDétails
Selenium is a chalcogen between sulfur and tellurium, with chemistry that commonly parallels both. It is a trace element required by many organisms because it is incorporated into selenoproteins, yet the margin between nutritional requirement and toxicity is narrow. Industrially, selenium is valued for its semiconductor and photoconductive behavior, its red color in glass, and its role in metallurgy and specialty chemicals.
Selenium exists in several allotropic forms, although three are generally recognized. Selenium can be prepared with either an amorphous or a crystalline structure. The color of amorphous selenium is either red (in powder form) or black (in vitreous form). Crystalline monoclinic selenium is a deep red; crystalline hexagonal selenium, the most stable variety, is a metallic gray.
Selenium exhibits both photovoltaic action, where light is converted directly into electricity, and photoconductive action, where the electrical resistance decreases with increased illumination. These properties make selenium useful in the production of photocells and exposure meters for photographic use, as well as solar cells. Selenium is also able to convert a.c. electricity to d.c., and is extensively used in rectifiers. Below its melting point, selenium is a p-type semiconductor and has many uses in electronic and solid-state applications.
Elemental selenium has been said to be practically nontoxic and is considered to be an essential trace element; however, hydrogen selenide and other selenium compounds are extremely toxic, and resemble arsenic in their physiological reactions.
The name derives from the Greek Selene, who was the Greek goddess of the Moon because the element is chemically found with tellurium (Tellus was the Roman goddess of the Earth). Selenium was discovered by the Swedish chemist Jöns Jacob Berzelius in 1817, while trying to isolate tellurium in an impure sample.
Selenium was discovered by Jöns Jacob Berzelius, a Swedish chemist, in 1817 after analyzing an impurity that was contaminating the sulfuric acid (H2SO4) being produced at a particular factory in Sweden. Originally believing the material was tellurium, Berzelius eventually realized that it was actually a previously unknown element. Selenium occurs in minerals such as eucairite (CuAgSe), crooksite (CuThSe) and clausthalite (PbSe), but these minerals are too rare to use as a major source of selenium. Today, most selenium is obtained as a byproduct of refining copper.
From the Greek word Selene, moon. Discovered by Berzelius in 1817, who found it associated with tellurium (named for the earth).
Elemental selenium has several allotropes. The most familiar macroscopic forms are red amorphous selenium and gray trigonal selenium, a brittle, metallic-looking solid that is the most stable form at ordinary conditions. Black vitreous selenium can form by rapid cooling from the melt.
Selenium has been used in photocells, light meters, rectifiers, and xerographic photoreceptors, although many of these applications have been reduced by silicon and organic photoconductors. It is still used to decolorize or color glass, producing ruby-red glasses and counteracting green iron tints. Small additions improve machinability in some copper and steel alloys. Selenium compounds are used in pigments, rubber vulcanization chemistry, antifungal shampoos, and as reagents in organic synthesis.
Selenium's resistance to the flow of electricity is greatly affected by the amount of light shining on it. The brighter the light, the better selenium conducts electricity. This property has made selenium useful in devices that respond to the intensity of light, such as electric eyes, photo cells, light meters for cameras and copiers. Selenium can also produce electricity directly from sunlight and is used in solar cells. Selenium is also a semiconductor and is used in some types of solid-state electronics as well as in rectifiers, devices which convert alternating current electricity into direct current electricity. In addition to its use in electrical devices, selenium is also used to make a ruby-red color in glasses and enamels, as a photographic toner and as an additive to stainless steel.
Selenium forms few inorganic compounds, none of which are commercially important. They include selenious acid (H2SeO3), selenium dichloride (SeCl2) and selenium oxychloride (SeOCl2).
Selenium is used in Xerography for reproducing and copying documents, letters, etc. It is used by the glass industry to decolorize glass and to make ruby-colored glasses and enamels. It is also used as a photographic toner, and as an additive to stainless steel.
Isotopes in Earth/Planetary Science
Molecules, atoms, and ions of the stable isotopes of selenium possess slightly different physical and chemical properties, and they commonly will be fractionated during physical, chemical, and biological processes, giving rise to variations in isotopic abundances and in atomic weights. There are measureable variations in the isotopic abundances of selenium in natural terrestrial materials (Fig. IUPAC.34.1).
Isotopes in Industry
75Se (with a half-life of 120 days) is used for X-ray radiography of welds to visualize welds and ensure that each weld is appropriate for its purpose [274] P. Hayward, D. Currie. “Radiography of welds using seleniuim 75, Ir 192 and x-rays”, in Asia-Pacific Conference on NDT, Auckland, New Zealand (2006)..
Isotopes in Medicine
75Se-selenomethionine (organic compound that combines to form proteins, found in Brazil nuts and soybeans) has been used to study the production of digestive enzymes (biological catalysts that accelerates chemical reactions) [275] A. C. Colella, F. Pigorini. Br. J. Radiol.40, 662 (1967).. Selenium stable isotopes are used in metabolic studies to monitor selenium intake and output [276] C. A. Swanson, D. C. Reamer, C. Veillon, J. C. King, O. A. Levander. Am. J. Clin. Nutr.38, 169 (1983)., [277] Public Health Service Agency for Toxic Substances and Disease Registry. Toxicological Profile for Selenium, U.S. Department of Health and Human Services (2014), Feb. 26; http://www.atsdr.cdc.gov/ToxProfiles/tp92.pdf..
Isotopes Used as a Source of Radioactive Isotope(s)
77Se and 78Se are used to produce the therapeutic radioisotope 77Br via the 77Se (n, p) 77Br and the 78Se (n, 2p) 77Br reactions, respectively. 80Se is used to produce 80mBr via the reaction 80Se (n, p) 80mBr. The m the superscript of 80mBr indicates a metastable state of the isotope.
Selenium occurs in oxidation states from −2 to +6, with −2, +4, and +6 especially important. Hydrogen selenide, H₂Se, is a highly toxic gas and the selenium analogue of hydrogen sulfide. Selenium dioxide, SeO₂, is a useful oxidizing reagent and forms selenous acid, H₂SeO₃, in water. Selenates such as sodium selenate, Na₂SeO₄, resemble sulfates chemically but are biologically more active. Metal selenides are important semiconductors, including cadmium selenide, CdSe, and copper indium gallium selenide used in thin-film photovoltaics.
See more information at the Selenium compound page.
Selenium is essential in trace amounts, but excess intake can cause selenosis, with gastrointestinal effects, hair and nail changes, and a garlic-like breath odor from volatile metabolites. Elemental selenium is less acutely hazardous than many soluble selenite and selenate salts, but dust exposure should be controlled. Hydrogen selenide, H₂Se, is extremely poisonous, and industrial selenium fumes or aerosols require strict ventilation and monitoring.
Hydrogen selenide at a concentration of 1.5 ppm is intolerable to man. Selenium occurs in some solid in amounts sufficient to produce serious effects on animals feeding on plants, such as locoweed, grown in such soils. Exposure to selenium compounds (as Se) in air should not exceed 0.2 mg/m3 (8-hour time-weighted average - 40-hour week).
Selenium is widely dispersed in sulfide ores, sedimentary rocks, soils, and waters, usually at low concentrations. Weathering and irrigation can mobilize selenate and selenite, which are taken up by plants and can bioaccumulate in food webs. Some plants tolerate and concentrate selenium, while many others show toxicity only where soils or drainage waters are selenium-rich. Microorganisms can reduce soluble selenium species to less mobile elemental selenium or volatile methylated forms.
Selenium is not normally mined as a primary product. Most commercial supply is recovered as a by-product from anode slimes produced during electrolytic refining of copper, with smaller links to other nonferrous metal processing. Demand is spread across glass manufacture, metallurgy, chemicals, electronics, and thin-film photovoltaic materials, so supply depends strongly on copper refining rather than direct selenium ore availability. Substitution has reduced some older electrical uses, but recovery remains economically useful because selenium is concentrated in refinery residues. Recycling occurs mainly through industrial scrap and process residues rather than consumer products.
Obtained from lead, copper and nickel refining. Conducts electricity when struck by light.
Selenium is a relatively uncommon cosmic element compared with lighter chalcogens. Its stable isotopes are produced mainly by neutron-capture processes in evolved stars and supernova-related environments, with contributions from both slow and rapid neutron capture. In planetary materials it behaves partly as a chalcophile element, tending to associate with sulfides rather than silicate minerals.
- Gray selenium conducts electricity better when illuminated.
- Selenium can replace sulfur in some amino acids, forming selenocysteine and selenomethionine.
- The smell associated with selenium exposure often comes from volatile methylated selenium compounds.
- Selenium was identified in residues from sulfuric acid manufacture.
- Some selenium-rich plants can poison grazing animals on naturally seleniferous soils.
- Cadmium selenide quantum dots can emit size-tunable visible light.
Images
Propriétés
Propriétés physiques
- Rayon atomique (empirique)
- 115 pm Comparer : Rayon atomique (empirique) de tous les éléments →
- Rayon covalent
- 120 pm Comparer : Rayon covalent de tous les éléments →
- Rayon de van der Waals
- 190 pm Comparer : Rayon de van der Waals de tous les éléments →
- Rayon métallique
- 117 pm Comparer : Rayon métallique de tous les éléments →
- Masse volumique
- 4809 kg/m³ Comparer : Masse volumique de tous les éléments →
- Volume molaire
- 0,0165 L/mol
- Phase aux CNTP
- Solide Comparer : Phase aux CNTP de tous les éléments →
- Point de fusion
- 220,5 °C Comparer : Point de fusion de tous les éléments →
- Point d’ébullition
- 684,85 °C Comparer : Point d’ébullition de tous les éléments →
- Conductivité thermique
- 0,52 W/(m·K) Comparer : Conductivité thermique de tous les éléments →
- Capacité thermique massique
- 0,321 J/(g·K) Comparer : Capacité thermique massique de tous les éléments →
- Capacité thermique molaire
- 25,363 J/(mol·K) Comparer : Capacité thermique molaire de tous les éléments →
- Structure cristalline
- Hexagonal compact Comparer : Structure cristalline de tous les éléments →
Propriétés chimiques
- Électronégativité (Pauling)
- 2,55 Comparer : Électronégativité (Pauling) de tous les éléments →
- Électronégativité (Allen)
- 2,424
- Affinité électronique
- 2,0206 eV
- Énergie d’ionisation (1re)
- 9,752368 eV Comparer : Énergie d’ionisation (1re) de tous les éléments →
- Énergie d’ionisation (2e)
- 21,196073 eV Comparer : Énergie d’ionisation (2e) de tous les éléments →
- Énergie d’ionisation (3e)
- 31,697109 eV Comparer : Énergie d’ionisation (3e) de tous les éléments →
- Énergie d’ionisation (4e)
- 42,947148 eV Comparer : Énergie d’ionisation (4e) de tous les éléments →
- Énergie d’ionisation (5e)
- 68,300235 eV Comparer : Énergie d’ionisation (5e) de tous les éléments →
- États d’oxydation
- −2, −1, 0, +1, +2, +3, +4, +5, +6 Comparer : États d’oxydation de tous les éléments →
- Électrons de valence
- 6 Comparer : Électrons de valence de tous les éléments →
- Allotropes
- ["gray", "vitreous"]
- Configuration électronique
- [Ar] 4s2 3d10 4p4
Propriétés thermodynamiques
- Point critique (température)
- 1493 °C
- Enthalpie de fusion
- 0,0693372 eV Comparer : Enthalpie de fusion de tous les éléments →
- Enthalpie de vaporisation
- 0,27258123 eV Comparer : Enthalpie de vaporisation de tous les éléments →
- Enthalpie de sublimation
- 2,352697 eV
- Enthalpie d’atomisation
- 2,352697 eV
- Enthalpie d’atomisation
- 2,35477 eV
Propriétés nucléaires
- Protons
- 34 Comparer : Protons de tous les éléments →
- Neutrons
- 46 Comparer : Neutrons de tous les éléments →
- Isotopes connus
- 33 Comparer : Isotopes connus de tous les éléments →
- Isotopes stables
- 4 Comparer : Isotopes stables de tous les éléments →
- Isotope le plus stable
- Se-80
- Année de découverte
- 1817
Abondance
- Abondance (croûte terrestre)
- 0,05 mg/kg Comparer : Abondance (croûte terrestre) de tous les éléments →
- Abondance (océan)
- 2 × 10−4 mg/L Comparer : Abondance (océan) de tous les éléments →
Structure cristalline
- Paramètre de maille a
- 436 pm
Structure électronique
- Électrons par couche
- 2, 8, 18, 6 Comparer : Électrons par couche de tous les éléments →
Identifiants
- Numéro CAS
- 7782-49-2 Comparer : Numéro CAS de tous les éléments →
- Symbole de terme
- 3P2
- InChI
- InChI=1S/Se
- Clé InChI
- BUGBHKTXTAQXES-UHFFFAOYSA-N
Configuration électronique Mesuré
Se: 3d¹⁰ 4s² 4p⁴[Ar] 3d¹⁰ 4s² 4p⁴1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁴Modèle 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
| Nombre de masse | Masse atomique (u) | Abondance naturelle | Demi-vie |
|---|---|---|---|
| 76 Stable | 75,919213704 ± 0,000000017 | 9,3700% | Stable |
| 77 Stable | 76,919914154 ± 0,000000067 | 7,6300% | Stable |
| 78 Stable | 77,91730928 ± 0,0000002 | 23,7700% | Stable |
| 80 Stable | 79,9165218 ± 0,0000013 | 49,6100% | Stable |
Phase / État
Explication: 195,5 °C en dessous du point de fusion (220,5 °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
Énergie nécessaire pour sublimer 1 mol au point de sublimation
Masse volumique
Dans les conditions standard
Dans les conditions standard
Données avancées
Spectres atomiques
Affichage de 10 sur 34. Tri par charge ionique croissante.
Raies répertoriées ?
| Ion | Charge | Nombre total de raies | Probabilités de transition | Désignations des niveaux |
|---|---|---|---|---|
| Se I | 0 | 138 | 0 | 0 |
| Se II | +1 | 39 | 0 | 0 |
| Se III | +2 | 39 | 0 | 0 |
| Se IV | +3 | 22 | 0 | 0 |
| Se V | +4 | 17 | 0 | 0 |
Niveaux répertoriés ?
| Ion | Charge | Niveaux |
|---|---|---|
| Se I | 0 | 173 |
| Se II | +1 | 78 |
| Se III | +2 | 53 |
| Se IV | +3 | 29 |
| Se V | +4 | 15 |
| Se VI | +5 | 7 |
| Se VII | +6 | 45 |
| Se VIII | +7 | 37 |
| Se IX | +8 | 2 |
| Se X | +9 | 2 |
Rayons ioniques
| Charge | Coordinence | Spin | Rayon |
|---|---|---|---|
| -2 | 6 | N/D | 198 pm |
| +4 | 6 | N/D | 50 pm |
| +6 | 4 | N/D | 28.000000000000004 pm |
| +6 | 6 | N/D | 42 pm |
Composés
Isotopes (4)
Naturally selenium contains six stable isotopes. Fifteen other isotopes have been characterized. The element is a member of the sulfur family and resembles sulfur both in its various forms and in its compounds.
| Nombre de masse | Masse atomique (u) | Abondance naturelle | Demi-vie | Mode de désintégration | |
|---|---|---|---|---|---|
| 76 Stable | 75,919213704 ± 0,000000017 | 9,3700% ± 0,2900% | Stable | stable | |
| 77 Stable | 76,919914154 ± 0,000000067 | 7,6300% ± 0,1600% | Stable | stable | |
| 78 Stable | 77,91730928 ± 0,0000002 | 23,7700% ± 0,2800% | Stable | stable | |
| 80 Stable | 79,9165218 ± 0,0000013 | 49,6100% ± 0,4100% | Stable | stable |
Propriétés étendues
Rayons covalents (données étendues)
- Rayon covalent (Pyykkö)
- 116 pm
- Rayon covalent (Pyykkö, liaison double)
- 107 pm
- Rayon covalent (Pyykkö, liaison triple)
- 107 pm
- Rayon covalent (Bragg)
- 117 pm
Rayons de van der Waals
- Bondi
- 190 pm
- Batsanov
- 190 pm
- Alvarez
- 182 pm
- UFF
- 420,5 pm
- MM3
- 229 pm
- Dreiding
- 403 pm
Rayons atomiques et métalliques
- Rayon atomique (Rahm)
- 224 pm
- Rayon métallique (C12)
- 140 pm
Échelles de numérotation
- Mendeleev
- 101
- Pettifor
- 93
- Glawe
- 95
Échelles d’électronégativité
- Ghosh
- 0
- Gunnarsson–Lundqvist
- 6
- Robles–Bartolotti
- 5
Polarisabilité et dispersion
- Polarisabilité dipolaire
- 28,9 a.u.
- Polarisabilité dipolaire (incertitude)
- 1 a.u.
- C₆
- 210 Ha·Bohr6
- C₆ (Gould–Bučko)
- 233 Ha·Bohr6
Risque d’approvisionnement et économie
- Concentration de la production
- 35
- Risque relatif d’approvisionnement
- 7
- Répartition des réserves
- 22
- Stabilité politique (principal producteur)
- 77
- Stabilité politique (principal détenteur de réserves)
- 18
Transitions de phase et allotropes
| Température de transition | 453,15 K |
| Point d’ébullition | 958,15 K |
| Point critique (température) | 1766,15 K |
| Point de fusion | 493,95 K |
| Point d’ébullition | 958,15 K |
| Point critique (température) | 1766,15 K |
| Point critique (pression) | 27,2 MPa |
Catégories d’états d’oxydation
Données de référence avancées
Constantes d’écran (8)
| n | Orbitale | σ |
|---|---|---|
| 1 | s | 0,7378 |
| 2 | p | 3,9348 |
| 2 | s | 9,1116 |
| 3 | d | 15,523 |
| 3 | p | 15,295 |
| 3 | s | 14,5966 |
| 4 | p | 25,7128 |
| 4 | s | 24,2424 |
Détail des rayons cristallins (4)
| Charge | CN | Spin | rcrystal (pm) | Origine |
|---|---|---|---|---|
| -2 | VI | 184 | Pauling's (1960) crystal radius, | |
| 4 | VI | 64 | Ahrens (1952) ionic radius, | |
| 6 | IV | 42 | ||
| 6 | VI | 56 | calculated, |
Modes de désintégration des isotopes (52)
| Isotope | Mode | Intensité |
|---|---|---|
| 63 | B+ | 100% |
| 63 | B+p | 89% |
| 63 | 2p | 0,5% |
| 64 | B+ | — |
| 64 | B+p | — |
| 65 | B+ | 100% |
| 65 | B+p | 87% |
| 66 | B+ | 100% |
| 66 | B+p | — |
| 67 | B+ | 100% |
Facteurs de diffusion des rayons X (506)
| Énergie (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 5,20241 |
| 10,1617 | — | 5,36005 |
| 10,3261 | — | 5,52247 |
| 10,4931 | — | 5,63017 |
| 10,6628 | — | 5,66221 |
| 10,8353 | — | 5,69443 |
| 11,0106 | — | 5,71762 |
| 11,1886 | — | 5,72709 |
| 11,3696 | — | 5,73659 |
| 11,5535 | — | 5,7461 |
Données complémentaires
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
5×10-2 milligrams per kilogram
Références (1)
- [5] Selenium https://education.jlab.org/itselemental/ele034.html
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
2×10-4 milligrams per liter
Références (1)
- [5] Selenium https://education.jlab.org/itselemental/ele034.html
Production
Production of this element (from raw materials or other compounds containing the element).
Selenium is found in a few rare minerals such as crooksite and clausthalite. In years past it has been obtained from flue dusts remaining from processing copper sulfide ores, but the anode metal from electrolytic copper refineries now provide the source of most of the world's selenium. Selenium is recovered by roasting the mud with soda or sulfuric acid, or by smelting them with soda and niter.
Références (1)
- [6] Selenium https://periodic.lanl.gov/34.shtml
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 Selenium.
The element property data was retrieved from publications.