Arsenic (As)
metalloidSolid
Standard Atomic Weight
74.921595 uElectron configuration
[Ar] 4s2 3d10 4p3Melting point
816.85 °CBoiling point
613.85 °CDensity
5776 kg/m³Oxidation states
−3, −2, −1, 0, +1, +2, +3, +4, +5Electronegativity (Pauling)
2.18Ionization energy (1st)
9.78855 eVDiscovery year
1250Atomic radius
115 pmDetails
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.
Images
Properties
Physical
- Atomic radius (empirical)
- 115 pm Compare Atomic radius (empirical) of all elements →
- Covalent radius
- 119 pm Compare Covalent radius of all elements →
- Van der Waals radius
- 185 pm Compare Van der Waals radius of all elements →
- Metallic radius
- 121 pm Compare Metallic radius of all elements →
- Density
- 5776 kg/m³ Compare Density of all elements →
- Molar volume
- 0.0131 L/mol
- Phase at STP
- Solid Compare Phase at STP of all elements →
- Melting point
- 816.85 °C Compare Melting point of all elements →
- Boiling point
- 613.85 °C Compare Boiling point of all elements →
- Specific heat capacity
- 0.329 J/(g·K) Compare Specific heat capacity of all elements →
- Molar heat capacity
- 24.64 J/(mol·K) Compare Molar heat capacity of all elements →
- Crystal structure
- Rhombohedral Compare Crystal structure of all elements →
Chemical
- Electronegativity (Pauling)
- 2.18 Compare Electronegativity (Pauling) of all elements →
- Electronegativity (Allen)
- 2.211
- Electron affinity
- 0.81 eV
- Ionization energy (1st)
- 9.78855 eV Compare Ionization energy (1st) of all elements →
- Ionization energy (2nd)
- 18.589264 eV Compare Ionization energy (2nd) of all elements →
- Ionization energy (3rd)
- 28.349098 eV Compare Ionization energy (3rd) of all elements →
- Ionization energy (4th)
- 50.150173 eV Compare Ionization energy (4th) of all elements →
- Ionization energy (5th)
- 62.770216 eV Compare Ionization energy (5th) of all elements →
- Oxidation states
- −3, −2, −1, 0, +1, +2, +3, +4, +5 Compare Oxidation states of all elements →
- Valence electrons
- 5 Compare Valence electrons of all elements →
- Allotropes
- ["gray"]
- Electron configuration
- [Ar] 4s2 3d10 4p3
Thermodynamic
- Triple point (temperature)
- 817 °C
- Triple point (pressure)
- 3.7e+6 Pa
- Critical point (temperature)
- 1400 °C
- Critical point (pressure)
- 2.23e+7 Pa
- Heat of vaporization
- 0.36275069 eV Compare Heat of vaporization of all elements →
- Heat of sublimation
- 3.138312 eV
- Heat of atomization
- 3.138312 eV
- Atomization enthalpy
- 3.135202 eV
Nuclear
- Protons
- 33 Compare Protons of all elements →
- Neutrons
- 42 Compare Neutrons of all elements →
- Known isotopes
- 33 Compare Known isotopes of all elements →
- Stable isotopes
- 1 Compare Stable isotopes of all elements →
- Most stable isotope
- As-75
- Discovery year
- 1250
Abundance
- Abundance (Earth's crust)
- 1.8 mg/kg Compare Abundance (Earth's crust) of all elements →
- Abundance (ocean)
- 3.7 mg/L Compare Abundance (ocean) of all elements →
Crystal Structure
- Lattice constant a
- 413 pm
Electronic Structure
- Electrons per shell
- 2, 8, 18, 5 Compare Electrons per shell of all elements →
Identifiers
- CAS number
- 7440-38-2 Compare CAS number of all elements →
- Term symbol
- 4S°3/2
- InChI
- InChI=1S/As
- InChI Key
- RQNWIZPPADIBDY-UHFFFAOYSA-N
Electron Configuration Measured
As: 3d¹⁰ 4s² 4p³[Ar] 3d¹⁰ 4s² 4p³1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³Atomic model
Isotopes change neutron count, mass, and stability — not the electron configuration of a neutral atom.
Schematic atomic model, not to scale.
Atomic Fingerprint
Emission / Absorption Spectrum
Isotope Distribution
| Mass number | Atomic mass (u) | Natural abundance | Half-life |
|---|---|---|---|
| 75 Stable | 74.92159457 ± 0.00000095 | 100.0000% | Stable |
Phase / State
Reason: 588.9 °C below sublimation point (613.85 °C)
Schematic, not to scale
Phase transition points
Transition energies
Energy required to vaporize 1 mol at boiling point
Energy required to sublime 1 mol at sublimation point
Density
At standard conditions
At standard conditions
Advanced
Atomic Spectra
Showing 10 of 33. Sorted by ion charge (ascending).
Lines Holdings ?
| Ion | Charge | Total lines | Transition probabilities | Level designations |
|---|---|---|---|---|
| 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 |
Levels Holdings ?
| Ion | Charge | Levels |
|---|---|---|
| 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 |
Ionic Radii
| Charge | Coordination | Spin | Radius |
|---|---|---|---|
| +3 | 6 | N/A | 57.99999999999999 pm |
| +5 | 4 | N/A | 33.5 pm |
| +5 | 6 | N/A | 46 pm |
Compounds
Isotopes (1)
| Mass number | Atomic mass (u) | Natural abundance | Half-life | Decay mode | |
|---|---|---|---|---|---|
| 75 Stable | 74.92159457 ± 0.00000095 | 100.0000% | Stable | stable |
Extended Properties
Covalent Radii (Extended)
- Covalent radius (Pyykkö)
- 121 pm
- Covalent radius (Pyykkö, double)
- 114 pm
- Covalent radius (Pyykkö, triple)
- 106 pm
- Covalent radius (Bragg)
- 126 pm
Van der Waals Radii
- Bondi
- 185 pm
- Batsanov
- 205 pm
- Alvarez
- 188 pm
- UFF
- 423 pm
- MM3
- 236 pm
- Dreiding
- 415 pm
Atomic & Metallic Radii
- Atomic radius (Rahm)
- 231 pm
- Metallic radius (C12)
- 148 pm
Numbering Scales
- Mendeleev
- 95
- Pettifor
- 89
- Glawe
- 90
Electronegativity Scales
- Ghosh
- 0
- Miedema
- 5
- Gunnarsson–Lundqvist
- 5
- Robles–Bartolotti
- 4
Polarizability & Dispersion
- Dipole polarizability
- 30 a.u.
- Dipole polarizability (unc.)
- 1 a.u.
- C₆
- 246 Ha·Bohr6
- C₆ (Gould–Bučko)
- 260 Ha·Bohr6
Miedema Parameters
- Miedema molar volume
- 11.85 cm3/mol
- Miedema electron density
- 3
Supply Risk & Economics
- Production concentration
- 64
- Relative supply risk
- 8
- Political stability (top producer)
- 24
Phase Transitions & Allotropes
| Melting point | 1090.15 K |
| Boiling point | 889.15 K |
| Critical point (temperature) | 1673.15 K |
| Critical point (pressure) | 22.3 MPa |
| Triple point (temperature) | 1090.15 K |
| Triple point (pressure) | 3700 kPa |
Oxidation State Categories
Advanced Reference Data
Screening Constants (8)
| n | Orbital | 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 |
Crystal Radii Detail (3)
| Charge | CN | Spin | rcrystal (pm) | Origin |
|---|---|---|---|---|
| 3 | VI | 72 | Ahrens (1952) ionic radius, | |
| 5 | IV | 47.5 | from r^3 vs V plots, | |
| 5 | VI | 60 | calculated, |
Isotope Decay Modes (50)
| Isotope | Mode | Intensity |
|---|---|---|
| 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% |
X‑ray Scattering Factors (506)
| Energy (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 |
Additional Data
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
1.8 milligrams per kilogram
References (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
3.7-3 milligrams per liter
References (1)
References
(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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This section provides all form of data related to element Arsenic.
The element property data was retrieved from publications.