| Atomic Mass | 74.921595 |
|---|---|
| Electron Configuration | [Ar]4s23d104p3 |
| Oxidation States | +5, +3, -3 |
| Year Discovered | Ancient |
| Atomic Mass | 74.921595 |
|---|---|
| Electron Configuration | [Ar]4s23d104p3 |
| Oxidation States | +5, +3, -3 |
| Year Discovered | Ancient |
| Element Name | Arsenic |
|---|---|
| Element Symbol | As |
| InChI | InChI=1S/As |
| InChIKey | RQNWIZPPADIBDY-UHFFFAOYSA-N |
| Atomic Weight |
74.921 595(6) 74.921595 74.92 74.921595(6) |
|---|---|
| Electron Configuration |
[Ar]4s23d104p3 |
| Atomic Radius |
Van der Waals Atomic Radius : 185 pm (Van der Waals) Empirical Atomic Radius : 115pm (Empirical) Covalent Atomic Radius : 119(4) pm (Covalent) |
| Oxidation States |
+5, +3, -3 5, 4, 3, 2, 1, -1, -2, -3 (a mildly acidic oxide) |
| Ground Level |
4S°3/2 |
| Ionization Energy |
9.815 eV 9.78855 ± 0.00025 eV |
| Electronegativity |
Pauling Scale Electronegativity : 2.18(Pauling Scale) Allen Scale Electronegativity : 2.211(Allen Scale) |
| Electron Affinity |
0.81eV 1.07eV |
| Atomic Spectra |
Lines Holdings Levels Holdings |
| Physical Description |
Solid |
| Element Classification |
Semi-metal |
| Element Period Number |
4 |
| Element Group Number |
15 - Pnictogen |
| Density |
5.776 grams per cubic centimeter |
| Melting Point |
1090 K (817°C or 1503°F) ~817°C |
| Boiling Point |
887 K (614°C or 1137°F) 603°C |
| Estimated Crustal Abundance |
1.8 milligrams per kilogram |
| Estimated Oceanic Abundance |
3.7-3 milligrams per liter |
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.
| Year | Atomic Weight (uncertainty) [u] | Reference |
|---|---|---|
| 2013 | 74.921 595(6) | https://doi.org/10.1515/pac-2015-0305 |
| 1995 | 74.921 60(2) | https://doi.org/10.1351/pac199668122339 |
| 1985 | 74.921 59(2) | https://doi.org/10.1351/pac198658121677 |
| 1969 | 74.9216(1) | https://doi.org/10.1351/pac197021010091 |
| 1961 | 74.9216 | https://doi.org/10.1021/ja00881a001 |
| 1934 | 74.91 | https://doi.org/10.1039/JR9340000499 |
| 1931 | 74.93 | https://doi.org/10.1039/JR9310001617 |
| 1910 | 74.96 | https://doi.org/10.1021/ja01919a001 |
| 1902 | 75.0 | https://doi.org/10.1007/BF01370337 |
| Year | Isotope | Abundance (uncertainty) | Reference |
|---|
| 1975, 75As, 1, doi:10.1351/pac197647010075 |
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.
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.
See more information at the Arsenic compound page.
| CID | Name | Formula | SMILES | Molecular Weight |
|---|---|---|---|---|
| 5359596 | arsenic | As | [As] | 74.92159 |
| 104734 | arsenic(3+) | As+3 | [As+3] | 74.92159 |
| 104737 | arsenic(5+) | As+5 | [As+5] | 74.92159 |
| 6335515 | arsenic-74 | As | [74As] | 73.92393 |
| 6335804 | arsenic-76 | As | [76As] | 75.922392 |
| 6336622 | arsenic-73 | As | [73As] | 72.92383 |
| 6337054 | arsenic-77 | As | [77As] | 76.92065 |
| 6337076 | arsenic-72 | As | [72As] | 71.92675 |
| 6337599 | arsenic-71 | As | [71As] | 70.92711 |
| 6337077 | arsenic-78 | As | [78As] | 77.9218 |
| 6337554 | arsenic-70 | As | [70As] | 69.93093 |
| 155926124 | arsenic-75 | As | [75As] | 74.921595 |
| 6337553 | arsenic-69 | As | [69As] | 68.9322 |
| 156022702 | arsenic-75(3+) | As+3 | [75As+3] | 74.921595 |
| 156022703 | arsenic-75(5+) | As+5 | [75As+5] | 74.921595 |
| 9855442 | arsenic(1+) | As+ | [As+] | 74.92159 |
| Stable Isotope Count | 1 |
|---|
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]. 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]. Inhalation of dust or smoke containing 74As is thought to be a causal agent of lung cancer. In one study [271], 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.
![Fig. IUPAC.33.1: Combined urine and fecal elimination of inhaled ⁷⁴As over a 10-day period. The ratio of urine to fecal elimination was approximately 30 to 1 (modified from [271]).](https://pubchem.ncbi.nlm.nih.gov/images/iupac/j_pac-2015-0703_fig_051.jpg)
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]. 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].
| Isotope | Atomic Mass (uncertainty) [u] | Abundance (uncertainty) |
|---|---|---|
| 75As | 74.921 595(6) | 1 |
| Isotope | Atomic Mass (uncertainty) [u] | Abundance (uncertainty) |
|---|---|---|
| 75As | 74.92159457(95) | 1 |
| Nuclide | Atomic Mass and Uncertainty [u] | Half Life and Uncertainty | Discovery Year | Decay Modes, Intensities and Uncertainties [%] |
|---|---|---|---|---|
| 60As | 59.993945 ± 0.000429 [Estimated] | Not-specified | p ? | |
| 60Asm | 59.993945 ± 0.000429 [Estimated] | Not-specified | p ? | |
| 61As | 60.981535 ± 0.000322 [Estimated] | Not-specified | p ? | |
| 62As | 61.973784 ± 0.000322 [Estimated] | Not-specified | p ? | |
| 63As | 62.964036 ± 0.000215 [Estimated] | Not-specified <43ns | p ? | |
| 64As | 63.957560 ± 0.000218 [Estimated] | 69.0 ms ± 1.4 | 1995 | β+=100%; β+p ? |
| 65As | 64.949611000 ± 0.000091 | 130.3 ms ± 0.6 | 1991 | β+=100%; β+p ? |
| 66As | 65.944148778 ± 0.0000061 | 95.77 ms ± 0.23 | 1978 | β+=100% |
| 66Asm | 65.944148778 ± 0.0000061 | 1.14 us ± 0.04 | 1995 | IT=100% |
| 66Asn | 65.944148778 ± 0.0000061 | 7.98 us ± 0.26 | 1998 | IT=100% |
| 67As | 66.939251110 ± 0.000000475 | 42.5 s ± 1.2 | 1980 | β+=100% |
| 68As | 67.936774127 ± 0.000001981 | 151.6 s ± 0.8 | 1971 | β+=100% |
| 68Asm | 67.936774127 ± 0.000001981 | 111 ns ± 20 | 1994 | IT=100% |
| 69As | 68.932246289 ± 0.000034352 | 15.2 m ± 0.2 | 1955 | β+=100% |
| 70As | 69.930934642 ± 0.0000015 | 52.6 m ± 0.3 | 1950 | β+=100% |
| 70Asm | 69.930934642 ± 0.0000015 | 96 us ± 3 | 1979 | IT=100% |
| 71As | 70.927113594 ± 0.000004469 | 65.30 h ± 0.07 | 1939 | β+=100% |
| 72As | 71.926752291 ± 0.000004383 | 26.0 h ± 0.1 | 1939 | β+=100% |
| 73As | 72.923829086 ± 0.000004136 | 80.30 d ± 0.06 | 1948 | ε=100% |
| 73Asm | 72.923829086 ± 0.000004136 | 5.7 us ± 0.2 | 1956 | IT=100% |
| 74As | 73.923928596 ± 0.000001817 | 17.77 d ± 0.02 | 1938 | β+=66±0.2%; β-=34±0.2% |
| 75As | 74.921594562 ± 0.000000948 | Stable | 1920 | IS=100% |
| 75Asm | 74.921594562 ± 0.000000948 | 17.62 ms ± 0.23 | 1957 | IT=100% |
| 76As | 75.922392011 ± 0.000000951 | 1.0933 d ± 0.0038 | 1934 | β-=100% |
| 76Asm | 75.922392011 ± 0.000000951 | 1.84 us ± 0.06 | 1966 | IT=100% |
| 77As | 76.920647555 ± 0.000001816 | 38.79 h ± 0.05 | 1951 | β-=100% |
| 77Asm | 76.920647555 ± 0.000001816 | 114.0 us ± 2.5 | 1957 | IT=100% |
| 78As | 77.921827771 ± 0.000010498 | 90.7 m ± 0.2 | 1937 | β-=100% |
| 79As | 78.920948419 ± 0.000005716 | 9.01 m ± 0.15 | 1950 | β-=100% |
| 79Asm | 78.920948419 ± 0.000005716 | 1.21 us ± 0.01 | 1998 | IT=100% |
| 80As | 79.922474440 ± 0.000003578 | 15.2 s ± 0.2 | 1954 | β-=100% |
| 81As | 80.922132288 ± 0.000002838 | 33.3 s ± 0.8 | 1960 | β-=100% |
| 82As | 81.924738731 ± 0.000004003 | 19.1 s ± 0.5 | 1968 | β-=100% |
| 82Asm | 81.924738731 ± 0.000004003 | 13.6 s ± 0.4 | 1970 | β-=100% |
| 83As | 82.925206900 ± 0.000003004 | 13.4 s ± 0.4 | 1968 | β-=100% |
| 84As | 83.929303290 ± 0.000003403 | 3.16 s ± 0.58 | 1968 | β-=100%; β-n=0.28±0.4% |
| 84Asm | 83.929303290 ± 0.000003403 | 650 ms ± 150 | 1974 | β-=100% |
| 85As | 84.932163658 ± 0.000003304 | 2.022 s ± 0.007 | 1967 | β-=100%; β-n=62.6±0.9% |
| 86As | 85.936701532 ± 0.000003703 | 945 ms ± 8 | 1973 | β-=100%; β-n=35.5±0.6%; β-2n ? |
| 87As | 86.940291716 ± 0.000003204 | 492 ms ± 25 | 1970 | β-=100%; β-n=15.4±2.2%; β-2n ? |
| 88As | 87.945840 ± 0.000215 [Estimated] | 270 ms ± 150 | 1994 | β-=100%; β-n ? |
| 89As | 88.950048 ± 0.000322 [Estimated] | 220 ms >150ns [Estimated] | 1994 | β- ?; β-n ?; β-2n ? |
| 90As | 89.955995 ± 0.000429 [Estimated] | 70 ms >300ns [Estimated] | 1997 | β- ?; β-n ?; β-2n ? |
| 90Asm | 89.955995 ± 0.000429 [Estimated] | 220 ns ± 100 | 2012 | IT=100% |
| 91As | 90.960816 ± 0.000429 [Estimated] | 100 ms >300ns [Estimated] | 1997 | β- ?; β-n ?; β-2n ? |
| 92As | 91.967386 ± 0.000537 [Estimated] | 45 ms >300ns [Estimated] | 1997 | β- ?; β-n ?; β-2n ? |
