Arsenic (33As) has 33 known isotopes and at least 10 isomers. Only one of these isotopes, 75As, is stable; as such, it is considered a monoisotopic element. The longest-lived radioisotope is 73As has a half-life of 80 days. Arsenic has been proposed as a "salting" material for nuclear weapons (cobalt is another, better-known salting material). A jacket of 75As, irradiated by the intense highenergy neutron flux from an exploding thermonuclear weapon, would transmute into the radioactive isotope 76As with a half-life of 1.0778 days and produce approximately 1.13 MeV gamma radiation, significantly increasing the radioactivity of the weapon's fallout for several hours. Such a weapon is not known to have ever been built, tested, or used.
|Main isotopes of arsenic (33As)|
|Standard atomic weight Ar, standard(As)|
isotopic mass (u)
|range of natural|
|66m1As||1356.70(17) keV||1.1(1) µs||(5+)|
|66m2As||3023.9(3) keV||8.2(5) µs||(9+)|
|68mAs||425.21(16) keV||111(20) ns
|70mAs||32.008(23) keV||96(3) µs||2(+)|
|74As||33||41||73.9239287(25)||17.77(2) d||β+ (66%)||74Ge||2−|
|75mAs||303.9241(7) keV||17.62(23) ms||9/2+|
|76As||33||43||75.922394(2)||1.0942(7) d||β− (99.98%)||76Se||2−|
|76mAs||44.425(1) keV||1.84(6) µs||(1)+|
|77mAs||475.443(16) keV||114.0(25) µs||9/2+|
|79mAs||772.81(6) keV||1.21(1) µs||(9/2)+|
|82mAs||250(200) keV||13.6(4) s||β−||82Se||(5-)|
|84As||33||51||83.92906(32)#||4.02(3) s||β− (99.721%)||84Se||(3)(+#)|
|β−, n (.279%)||83Se|
|84mAs||0(100)# keV||650(150) ms|
|85As||33||52||84.93202(21)#||2.021(10) s||β−, n (59.4%)||84Se||(3/2−)#|
|86As||33||53||85.93650(32)#||0.945(8) s||β− (67%)||86Se|
|β−, n (33%)||85Se|
|87As||33||54||86.93990(32)#||0.56(8) s||β− (84.6%)||87Se||3/2−#|
|β−, n (15.4%)||86Se|
Arsenic is a chemical element with symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, but only the gray form, which has a metallic appearance, is important to industry.
The primary use of arsenic is in alloys of lead (for example, in car batteries and ammunition). Arsenic is a common n-type dopant in semiconductor electronic devices, and the optoelectronic compound gallium arsenide is the second most commonly used semiconductor after doped silicon. Arsenic and its compounds, especially the trioxide, are used in the production of pesticides, treated wood products, herbicides, and insecticides. These applications are declining due to the toxicity of arsenic and its compounds.A few species of bacteria are able to use arsenic compounds as respiratory metabolites. Trace quantities of arsenic are an essential dietary element in rats, hamsters, goats, chickens, and presumably other species. A role in human metabolism is not known. However, arsenic poisoning occurs in multicellular life if quantities are larger than needed. Arsenic contamination of groundwater is a problem that affects millions of people across the world.
The United States' Environmental Protection Agency states that all forms of arsenic are a serious risk to human health. The United States' Agency for Toxic Substances and Disease Registry ranked arsenic as number 1 in its 2001 Priority List of Hazardous Substances at Superfund sites. Arsenic is classified as a Group-A carcinogen.Arsenic (disambiguation)
Arsenic is the chemical element with symbol As and atomic number 33.
Arsenic may also refer to:
Arsenic trioxide, a poison commonly referred to as simply as "arsenic"
Arsenic acid, a chemical compound with the formula H3AsO4
Arsenic Lake, a lake in Ontario, Canada
Ärsenik, a French rap group
Mr. Arsenic, an America anthology television seriesSelenium
Selenium is a chemical element with symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic. It rarely occurs in its elemental state or as pure ore compounds in the Earth's crust. Selenium (from Ancient Greek σελήνη (selḗnē) "Moon") was discovered in 1817 by Jöns Jacob Berzelius, who noted the similarity of the new element to the previously discovered tellurium (named for the Earth).
Selenium is found in metal sulfide ores, where it partially replaces the sulfur. Commercially, selenium is produced as a byproduct in the refining of these ores, most often during production. Minerals that are pure selenide or selenate compounds are known but rare. The chief commercial uses for selenium today are glassmaking and pigments. Selenium is a semiconductor and is used in photocells. Applications in electronics, once important, have been mostly replaced with silicon semiconductor devices. Selenium is still used in a few types of DC power surge protectors and one type of fluorescent quantum dot.
Selenium salts are toxic in large amounts, but trace amounts are necessary for cellular function in many organisms, including all animals. Selenium is an ingredient in many multivitamins and other dietary supplements, including infant formula. It is a component of the antioxidant enzymes glutathione peroxidase and thioredoxin reductase (which indirectly reduce certain oxidized molecules in animals and some plants). It is also found in three deiodinase enzymes, which convert one thyroid hormone to another. Selenium requirements in plants differ by species, with some plants requiring relatively large amounts and others apparently requiring none.