Arsenic (As)
metalloidSolid
Peso atomico standard
74,921595 uConfigurazione elettronica
[Ar] 4s2 3d10 4p3Punto di fusione
816,85 °CPunto di ebollizione
613,85 °CDensità
5776 kg/m³Stati di ossidazione
−3, −2, −1, 0, +1, +2, +3, +4, +5Elettronegatività (Pauling)
2,18Energia di ionizzazione (1ª)
9,78855 eVAnno della scoperta
1250Raggio atomico
115 pmDettagli
Arsenic is a metalloid in group 15, chemically related to phosphorus and antimony. It occurs mainly in sulfide minerals and in arsenide or sulfosalt ores, rather than as the native element. Its chemistry is dominated by the +3 and +5 oxidation states, with important differences in mobility and toxicity among species. Arsenic is technologically useful in small quantities, especially in compound semiconductors, but it is better known for the toxicity of many of its inorganic compounds.
The element is a steel gray, very brittle, crystalline, semimetallic solid; it tarnishes in air, and when it is heated it rapidly oxidizes to arsenous oxide, which smells of garlic. Arsenic and its compounds are poisonous.
The name derives from the Latin arsenicium and the Greek arsenikos for "masculine" or "male" because the ancients thought that metals were different sexes. Arsenic was known in prehistoric times for its poisonous sulfides. The German scientist and philosopher, Albert von Bollstadt (Albert the Great or Albertus Magnus) is thought to have obtained the metal around 1250.
Although arsenic compounds were mined by the early Chinese, Greek and Egyptian civilizations, it is believed that arsenic itself was first identified by Albertus Magnus, a German alchemist, in 1250. Arsenic occurs free in nature, but is most often found in the minerals arsenopyrite (FeAsS), realgar (AsS) and orpiment (As2S3). Today, most commercial arsenic is obtained by heating arsenopyrite.
From the Latin word arsenicum, Greek arsenikon. Elemental arsenic occurs in two solid modifications: yellow, and gray or metallic, with specific gravities of 1.97, and 5.73, respectively. It is believed that Albertus Magnus obtained the element in 1250 A.D. In 1649 Schroeder published two methods of preparing the element. Mispickel arsenopyrite, (FeSAs), is the most common mineral from which, on heating, the arsenic sublimes leaving ferrous sulfide.
Pure arsenic is most commonly encountered as gray arsenic, a brittle, metallic-looking solid with a steel-gray surface. It sublimes readily on heating rather than melting at ordinary pressure. Yellow and black allotropes are known but are less stable under ordinary conditions.
Elemental arsenic has limited direct use. Small additions have been used to harden lead alloys, especially for shot, grids, and some bearing materials. The most important modern use is in high-purity compound semiconductors, notably gallium arsenide (GaAs), which is used in radio-frequency electronics, optoelectronics, infrared devices, and some high-efficiency solar cells. Arsenic compounds were formerly used widely in pesticides, herbicides, wood preservatives, pigments, and medicines, but many such uses have been restricted or abandoned because of toxicity and persistence.
Arsenic and its compounds are poisonous. They have been used to make rat poison and some insecticides. Small amounts of arsenic are added to germanium to make transistors. Gallium arsenide (GaAs) can produce laser light directly from electricity.
If you were paying careful attention to the physical data listed above, you may have noticed that arsenic's boiling point is lower than its melting point. This occurs because these two temperatures are measured at different atmospheric pressures. When heated at standard atmospheric pressure, arsenic changes directly from a solid to a gas, or sublimates, at a temperature of 887 K. In order to form liquid arsenic, the atmospheric pressure must be increased. At 28 times standard atmospheric pressure, arsenic melts at a temperature of 1090 K. If it were also measured at a pressure of 28 atmospheres, arsenic's boiling point would be higher than its melting point, as you would expect.
Arsenic is used in bronzing, pyrotechny, and for hardening and improving the sphericity of shot. The most important compounds are white arsenic, the sulfide, Paris green, calcium arsenate, and lead arsenate; the last three have been used as agricultural insecticides and poisons. Marsh's test makes use of the formation and ready decomposition of arsine. Arsenic is finding increasing uses as a doping agent in solid-state devices such as transistors. Gallium arsenide is used as a laser material to convert electricity directly into coherent light.
Isotopes in Biology
73As and 76As (with half-lives of 80.3 days and 1.1 days, respectively) are important radioactive tracers used in environmental and biomedical studies to quantify arsenic uptake [270] J. De Kimpe, R. Cornelis, L. Mees, R. Vanholder. Fundam. Appl. Toxicol.34, 240 (1996).. 74As (with a half-life of 17.8 days) has been used to investigate the biotransformation (modification of a chemical compound by an organism) of arsenate by mammals. In one study rabbits were injected with 74As-labeled arsenate. After a given amount of time, blood and blood products were sampled and tested for the presence and quantity of labeled arsenate metabolites [270] J. De Kimpe, R. Cornelis, L. Mees, R. Vanholder. Fundam. Appl. Toxicol.34, 240 (1996).. Inhalation of dust or smoke containing 74As is thought to be a causal agent of lung cancer. In one study [271] R. H. Holland, M. S. McCall, H. C. Lanz. Cancer Res.19, 1154 (1959)., the “absorption rate from the bronchial tree (a respiratory tract, which conducts air into the lungs) was rapid for the first several days and then tapered off slowly. In three patients an average of 45 percent of the inhaled arsenic was eliminated in the urine in 10 days and about 0.5 percent in the stools. The remainder must be assumed to have been deposited in the body, exhaled, and/or eliminated in body secretions and excreta over a long period of time.” See Fig. IUPAC.33.1.
Isotopes in Medicine
72As (with a half-life of 26 h) and 74As are useful in molecular imaging because they are radioactive isotopes that emit positrons that can be designed to bind to monoclonal antibodies (moAb), which accumulate in tumors and then 72As- or 74As-labeled ligands will bind to the moAbs. Once the 72As- or 74As-labeled ligand binds to the moAb, positron emission tomography (PET) is used to visualize the exact location of the tumor [272] M. Jennewein, A. Hermanne, R. P. Mason, P. E. Thorpe, F. Rösch. Nucl. Instrum. Methods Phys. Res. A569, 512 (2006).. A specific example of using radiolabeled antibodies for better imaging of tumors is the combination of 74As with bavituximab, which is an antibody that binds strongly to unique lipids on the surface of tumors. When a thiol group is introduced to bavituximab, arsenic is able to bind covalently, creating a simple and elegant radio-label for targeting cancerous tumors [269] M. Jennewein, M. A. Lewis, D. Zhao, E. Tsyganov, N. Slavine, J. He, L. Watkins, V. D. Kodibagkar, S. O’Kelly, P. Kulkarni, P. P. Antich, A. Hermanne, F. Rösch, R. P. Mason, P. E. Thorpe. Clin. Cancer Res.14, 1377 (2008)..
Arsenic forms covalent and ionic compounds in several oxidation states, chiefly −3, +3, and +5. Arsenic trioxide (As₂O₃) is a major industrial intermediate and dissolves to give arsenite species. Arsenic pentoxide (As₂O₅) and arsenic acid (H₃AsO₄) contain arsenic in the +5 state and are related to arsenate salts. Arsine (AsH₃) is a highly toxic, volatile hydride. Important minerals include arsenopyrite (FeAsS), realgar (As₄S₄), and orpiment (As₂S₃). Organoarsenic compounds also exist, including methylated species found in biological and environmental systems.
See more information at the Arsenic compound page.
Arsenic metal is hazardous mainly through dust, fumes, and conversion to soluble or volatile compounds. Many inorganic arsenic(III) compounds are acutely toxic, and chronic exposure to inorganic arsenic in drinking water or industrial settings is associated with serious disease, including cancers. Arsine (AsH₃) is especially dangerous because it is a potent hemolytic gas. Toxicity depends strongly on chemical form, dose, route of exposure, and solubility; organic arsenic species in seafood are often much less toxic than inorganic arsenic.
Arsenic enters the environment through natural weathering of minerals, volcanic emissions, geothermal waters, and human activities such as mining, smelting, coal combustion, and historical pesticide use. In groundwater, its mobility is controlled by pH, redox conditions, adsorption to iron and manganese oxides, and microbial transformations. Arsenate species generally predominate under oxidizing conditions, while arsenite species are more important under reducing conditions and are often more mobile and toxic.
Arsenic is not usually mined as a primary commodity. It is recovered mainly as arsenic trioxide (As₂O₃) from flue dusts and residues generated during the smelting and refining of copper, lead, gold, and other nonferrous ores. Demand is much smaller than in the past because agricultural chemicals and chromated copper arsenate wood preservatives have been reduced or phased out in many regions. High-purity arsenic for gallium arsenide (GaAs) is a specialized market requiring stringent purification. Supply depends heavily on by-product recovery, environmental controls at smelters, and the ability to handle or stabilize arsenic-bearing wastes.
Found in mispickel (arsenopyrite)
Arsenic is a relatively uncommon element in the cosmos. Its stable isotope, ⁷⁵As, is produced by neutron-capture processes in evolved stars and supernova-related environments. In planetary materials, arsenic behaves as a moderately chalcophile and siderophile trace element, so it is commonly associated with sulfides and metallic phases rather than silicate minerals alone. Meteorites contain small amounts of arsenic in mineral and metal fractions.
- Natural arsenic consists essentially of one stable isotope, ⁷⁵As.
- Gray arsenic sublimes at ordinary pressure, which complicates simple melting-point measurements.
- Garlic-like odor during heating often comes from volatile arsenic compounds, not a safe warning sign.
- Arsenopyrite (FeAsS) is one of the most important arsenic-bearing ore minerals.
- Gallium arsenide (GaAs) has higher electron mobility than silicon, but it is costlier and more brittle.
- Some microorganisms can transform arsenic between arsenite, arsenate, and methylated forms.
Immagini
Proprietà
Fisiche
- Raggio atomico (empirico)
- 115 pm Confronta Raggio atomico (empirico) di tutti gli elementi →
- Raggio covalente
- 119 pm Confronta Raggio covalente di tutti gli elementi →
- Raggio di van der Waals
- 185 pm Confronta Raggio di van der Waals di tutti gli elementi →
- Raggio metallico
- 121 pm Confronta Raggio metallico di tutti gli elementi →
- Densità
- 5776 kg/m³ Confronta Densità di tutti gli elementi →
- Volume molare
- 0,0131 L/mol
- Fase in condizioni STP
- Solido Confronta Fase in condizioni STP di tutti gli elementi →
- Punto di fusione
- 816,85 °C Confronta Punto di fusione di tutti gli elementi →
- Punto di ebollizione
- 613,85 °C Confronta Punto di ebollizione di tutti gli elementi →
- Capacità termica specifica
- 0,329 J/(g·K) Confronta Capacità termica specifica di tutti gli elementi →
- Capacità termica molare
- 24,64 J/(mol·K) Confronta Capacità termica molare di tutti gli elementi →
- Struttura cristallina
- Romboedrica Confronta Struttura cristallina di tutti gli elementi →
Chimiche
- Elettronegatività (Pauling)
- 2,18 Confronta Elettronegatività (Pauling) di tutti gli elementi →
- Elettronegatività (Allen)
- 2,211
- Affinità elettronica
- 0,81 eV
- Energia di ionizzazione (1ª)
- 9,78855 eV Confronta Energia di ionizzazione (1ª) di tutti gli elementi →
- Energia di ionizzazione (2ª)
- 18,589264 eV Confronta Energia di ionizzazione (2ª) di tutti gli elementi →
- Energia di ionizzazione (3ª)
- 28,349098 eV Confronta Energia di ionizzazione (3ª) di tutti gli elementi →
- Energia di ionizzazione (4ª)
- 50,150173 eV Confronta Energia di ionizzazione (4ª) di tutti gli elementi →
- Energia di ionizzazione (5ª)
- 62,770216 eV Confronta Energia di ionizzazione (5ª) di tutti gli elementi →
- Stati di ossidazione
- −3, −2, −1, 0, +1, +2, +3, +4, +5 Confronta Stati di ossidazione di tutti gli elementi →
- Elettroni di valenza
- 5 Confronta Elettroni di valenza di tutti gli elementi →
- Allotropi
- ["gray"]
- Configurazione elettronica
- [Ar] 4s2 3d10 4p3
Termodinamiche
- Punto triplo (temperatura)
- 817 °C
- Punto triplo (pressione)
- 3,7e+6 Pa
- Punto critico (temperatura)
- 1400 °C
- Punto critico (pressione)
- 2,23e+7 Pa
- Calore di vaporizzazione
- 0,36275069 eV Confronta Calore di vaporizzazione di tutti gli elementi →
- Calore di sublimazione
- 3,138312 eV
- Calore di atomizzazione
- 3,138312 eV
- Entalpia di atomizzazione
- 3,135202 eV
Nucleari
- Protoni
- 33 Confronta Protoni di tutti gli elementi →
- Neutroni
- 42 Confronta Neutroni di tutti gli elementi →
- Isotopi noti
- 33 Confronta Isotopi noti di tutti gli elementi →
- Isotopi stabili
- 1 Confronta Isotopi stabili di tutti gli elementi →
- Isotopo più stabile
- As-75
- Anno della scoperta
- 1250
Abbondanza
- Abbondanza (crosta terrestre)
- 1,8 mg/kg Confronta Abbondanza (crosta terrestre) di tutti gli elementi →
- Abbondanza (oceano)
- 3,7 mg/L Confronta Abbondanza (oceano) di tutti gli elementi →
Struttura cristallina
- Costante reticolare a
- 413 pm
Struttura elettronica
- Elettroni per guscio
- 2, 8, 18, 5 Confronta Elettroni per guscio di tutti gli elementi →
Identificativi
- Numero CAS
- 7440-38-2 Confronta Numero CAS di tutti gli elementi →
- Simbolo di termine
- 4S°3/2
- InChI
- InChI=1S/As
- Chiave InChI
- RQNWIZPPADIBDY-UHFFFAOYSA-N
Configurazione elettronica Misurato
As: 3d¹⁰ 4s² 4p³[Ar] 3d¹⁰ 4s² 4p³1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³Modello atomico
Gli isotopi modificano il numero di neutroni, la massa e la stabilità — non la configurazione elettronica di un atomo neutro.
Modello atomico schematico, non in scala.
Impronta atomica
Spettro di emissione / assorbimento
Distribuzione isotopica
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita |
|---|---|---|---|
| 75 Stabile | 74,92159457 ± 0,00000095 | 100,0000% | Stabile |
Fase / Stato
Motivo: 588,9 °C sotto il punto di sublimazione (613,85 °C)
Schema non in scala
Punti di transizione di fase
Energie di transizione
Energia necessaria per vaporizzare 1 mol al punto di ebollizione
Energia necessaria per sublimare 1 mol al punto di sublimazione
Densità
In condizioni standard
In condizioni standard
Avanzate
Spettri atomici
Sono visualizzati 10 di 33. Ordinamento per carica ionica crescente.
Righe disponibili ?
| Ione | Carica | Righe totali | Probabilità di transizione | Designazioni dei livelli |
|---|---|---|---|---|
| As I | 0 | 52 | 14 | 51 |
| As II | +1 | 86 | 0 | 0 |
| As III | +2 | 14 | 0 | 0 |
| As IV | +3 | 8 | 0 | 0 |
| As V | +4 | 9 | 0 | 0 |
Livelli disponibili ?
| Ione | Carica | Livelli |
|---|---|---|
| As I | 0 | 116 |
| As II | +1 | 167 |
| As III | +2 | 22 |
| As IV | +3 | 34 |
| As V | +4 | 9 |
| As VI | +5 | 44 |
| As VII | +6 | 50 |
| As VIII | +7 | 2 |
| As IX | +8 | 2 |
| As X | +9 | 2 |
Raggi ionici
| Carica | Coordinazione | Spin | Raggio |
|---|---|---|---|
| +3 | 6 | N/D | 57.99999999999999 pm |
| +5 | 4 | N/D | 33.5 pm |
| +5 | 6 | N/D | 46 pm |
Composti
Isotopi (1)
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita | Modalità di decadimento | |
|---|---|---|---|---|---|
| 75 Stabile | 74,92159457 ± 0,00000095 | 100,0000% | Stabile | stable |
Proprietà estese
Raggi covalenti (dati estesi)
- Raggio covalente (Pyykkö)
- 121 pm
- Raggio covalente (Pyykkö, legame doppio)
- 114 pm
- Raggio covalente (Pyykkö, legame triplo)
- 106 pm
- Raggio covalente (Bragg)
- 126 pm
Raggi di van der Waals
- Bondi
- 185 pm
- Batsanov
- 205 pm
- Alvarez
- 188 pm
- UFF
- 423 pm
- MM3
- 236 pm
- Dreiding
- 415 pm
Raggi atomici e metallici
- Raggio atomico (Rahm)
- 231 pm
- Raggio metallico (C12)
- 148 pm
Scale di numerazione
- Mendeleev
- 95
- Pettifor
- 89
- Glawe
- 90
Scale di elettronegatività
- Ghosh
- 0
- Miedema
- 5
- Gunnarsson–Lundqvist
- 5
- Robles–Bartolotti
- 4
Polarizzabilità e dispersione
- Polarizzabilità dipolare
- 30 a.u.
- Polarizzabilità dipolare (inc.)
- 1 a.u.
- C₆
- 246 Ha·Bohr6
- C₆ (Gould–Bučko)
- 260 Ha·Bohr6
Parametri di Miedema
- Volume molare di Miedema
- 11,85 cm3/mol
- Densità elettronica di Miedema
- 3
Rischio di approvvigionamento ed economia
- Concentrazione della produzione
- 64
- Rischio relativo di approvvigionamento
- 8
- Stabilità politica (principale produttore)
- 24
Transizioni di fase e allotropi
| Punto di fusione | 1090,15 K |
| Punto di ebollizione | 889,15 K |
| Punto critico (temperatura) | 1673,15 K |
| Punto critico (pressione) | 22,3 MPa |
| Punto triplo (temperatura) | 1090,15 K |
| Punto triplo (pressione) | 3700 kPa |
Categorie degli stati di ossidazione
Dati di riferimento avanzati
Costanti di schermaggio (8)
| n | Orbitale | σ |
|---|---|---|
| 1 | s | 0,7217 |
| 2 | p | 3,9264 |
| 2 | s | 8,873 |
| 3 | d | 15,6216 |
| 3 | p | 15,1503 |
| 3 | s | 14,4045 |
| 4 | p | 25,5508 |
| 4 | s | 24,056 |
Dettaglio dei raggi cristallini (3)
| Carica | CN | Spin | rcrystal (pm) | Origine |
|---|---|---|---|---|
| 3 | VI | 72 | Ahrens (1952) ionic radius, | |
| 5 | IV | 47,5 | from r^3 vs V plots, | |
| 5 | VI | 60 | calculated, |
Modalità di decadimento degli isotopi (50)
| Isotopo | Modalità | Intensità |
|---|---|---|
| 60 | p | — |
| 61 | p | — |
| 62 | p | — |
| 63 | p | — |
| 64 | B+ | 100% |
| 64 | B+p | — |
| 65 | B+ | 100% |
| 65 | B+p | — |
| 66 | B+ | 100% |
| 67 | B+ | 100% |
Fattori di diffusione dei raggi X (506)
| Energia (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 4,62596 |
| 10,1617 | — | 4,67742 |
| 10,3261 | — | 4,72945 |
| 10,4931 | — | 4,78206 |
| 10,6628 | — | 4,83525 |
| 10,8353 | — | 4,88904 |
| 11,0106 | — | 4,94342 |
| 11,1886 | — | 4,99841 |
| 11,3696 | — | 5,05401 |
| 11,5535 | — | 5,11023 |
Dati aggiuntivi
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
1.8 milligrams per kilogram
Riferimenti (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
3.7-3 milligrams per liter
Riferimenti (1)
Riferimenti
(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 Arsenic.
The element property data was retrieved from publications.