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Element Arsenic (As), Group 15, Atomic Number 33, p-block, Mass 74.922. Sources, facts, uses, scarcity (SRI), podcasts, alchemical symbols, videos and images.
- Overview
- History
- Occurrence and distribution
- Commercial production and uses
arsenic (As), a chemical element in the nitrogen group (Group 15 [Va] of the periodic table), existing in both gray and yellow crystalline forms.
Arsenic was known in the form of certain of its compounds long before it was clearly recognized as a chemical element. In the 4th century bce Aristotle wrote of a substance called sandarache, now believed to have been the mineral realgar, a sulfide of arsenic. Then, in the 1st century ce, the writers Pliny the Elder and Pedanius Dioscorides both de...
The abundance of arsenic in the Earth’s crust is about five grams per ton; the cosmic abundance is estimated as about four atoms per million atoms of silicon. The element is widely distributed. A small amount exists in the native state, in 90–98 percent purity, generally in association with such metals as antimony and silver. Most, however, is combined in more than 150 different minerals, as sulfides, arsenides, sulfoarsenides, and arsenites. Mispickel, or arsenopyrite, FeAsS, is among the most common of arsenic-bearing minerals; others are realgar, As4S4; orpiment, As2S3; loellingite, FeAs2; and enargite, Cu3AsS4. Arsenic oxide is also common. Most commercial arsenic is recovered as a by-product of the smelting of copper, lead, cobalt, and gold ores.
Only one stable isotope of arsenic, that of mass 75, occurs in nature. Among the artificial radioactive isotopes is one of mass 76, which has a half-life of 26.4 hours. Arsenic-72, -74, and -76 have been used in medical diagnostic procedures.
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Metallic arsenic forms when arsenopyrite is heated at 650–700 °C in the absence of air. The arsenic in arsenopyrite and the arsenic impurities in other metal ores unite readily with oxygen when heated in air, forming the easily sublimed oxide, As4O6, also known as “white arsenic.” The vapour of the oxide is collected and condensed in a series of brick chambers and later purified by resublimation. Most arsenic is prepared by carbon reduction of the arsenious oxide dust thus collected.
World consumption of metallic arsenic is relatively small, only a few hundred tons per year. Most of what is consumed comes from Sweden. It is used in metallurgical applications because of its metalloid properties. About one percent arsenic content is desirable in the manufacture of lead shot, for example, because it improves the roundness of the molten drops. Bearing alloys based on lead are improved in both thermal and mechanical properties when they contain about 3 percent arsenic. A small amount of arsenic in lead alloys hardens them for use in batteries and cable sheathing. Small concentrations of arsenic improve the corrosion resistance and thermal properties of copper and brass. Elemental arsenic is also used in bronzing and in pyrotechnics.Very highly purified arsenic finds applications in semiconductor technology, where it is used with silicon and germanium, as well as in the form of gallium arsenide, GaAs, for diodes, lasers, and transistors.
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Because arsenic has a range of oxidation states from -3 to +5, it can form a variety of different kinds of compounds. Among the most important commercial compounds are the oxides, the principal forms of which are arsenious oxide (As4O6) and arsenic pentoxide (As2O5). Arsenious oxide, commonly known as white arsenic, is obtained as a by-product from the roasting of the ores of copper, lead, and certain other metals as well as by the roasting of arsenopyrite and arsenic sulfide ores. Arsenious oxide provides the starting material for most other arsenic compounds. It is also utilized in pesticides and serves as a decolourizer in the manufacture of glass and as a preservative for hides. Arsenic pentoxide is formed by the action of an oxidizing agent (e.g., nitric acid) on arsenious oxide. It comprises a major ingredient of insecticides, herbicides, and metal adhesives.
Arsine (AsH3), a colourless poisonous gas composed of arsenic and hydrogen, is another familiar arsenic compound. The gas, also called arsenic hydride, is produced by the hydrolysis of metal arsenides and by the reduction by metals of arsenic compounds in acidic solutions. It has been used as a doping agent for semi-conductors and as a military poison gas. Arsenic compounds of particular importance in agriculture are arsenic acid (H3AsO4) and such salts as lead arsenate (PbHAsO4) and calcium arsenate [Ca3(AsO4)2], which are useful for sterilizing soils and controlling pests, respectively.
- The Editors of Encyclopaedia Britannica
Arsenic is a chemical element; it has symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is a notoriously toxic heavy metal.
- metallic grey
- grey (most common), yellow, black (see Allotropes of arsenic)
Jul 3, 2019 · Get periodic table facts on the chemical and physical properties of the element arsenic, which is used as a doping agent in solid-state devices.
- Anne Marie Helmenstine, Ph.D.
Jul 28, 2016 · Arsenic is a crystalline metalloid found in the Earth's crust, but in its free form it is quite rare. The element is typically found in minerals, such as arsenopyrite, realgar and orpiment,...
- Traci Pedersen
Dec 3, 2023 · Arsenic is a chemical element with the symbol As and atomic number 33, making it a part of the pnictogen or nitrogen group in the periodic table. This metalloid element is notorious for its toxicity. Arsenic exhibits a wide range of properties and plays diverse roles in both ancient and modern times.
Arsenic is immediately dangerous to life or health at 5 mg m -3. Our bodies do not readily absorb the element itself, hence pure arsenic is much less dangerous than As (III) compounds such as AsH 3 and As 2 O 3 which are absorbed easily and are carcinogenic with high toxicity.
