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Arsenic is a chemical element with the symbol As and the 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 ubiquitous naturally occurring chemical element, and the 20th most common element on Earth. [13] Arsenic levels in the groundwater vary from around 0.5 parts per billion to 5000 parts per billion, depending on an area's geologic features, and possible presence on industrial waste.
Arsenic is used as the group 15 element in the III-V semiconductors gallium arsenide, indium arsenide, and aluminium arsenide. [10] The valence electron count of GaAs is the same as a pair of Si atoms, but the band structure is completely different which results in distinct bulk properties. [11]
Some arsenic exists in elemental form, but most arsenic is found in the arsenic minerals orpiment, realgar, arsenopyrite, and enargite. [ 14 ] Antimony makes up 0.2 parts per million of the earth's crust, making it the 63rd most abundant element.
Arsenic is a moderately abundant element in Earth's crust, and although many arsenic compounds are often considered highly toxic to most life, a wide variety of organoarsenic compounds are produced biologically and various organic and inorganic arsenic compounds are metabolized by numerous organisms.
Arsenic (33 As) has 32 known isotopes and at least 10 isomers. Only one of these isotopes, 75 As, is stable; as such, it is considered a monoisotopic element. The longest-lived radioisotope is 73 As with a half-life of 80 days.
Gray, or metallic arsenic, pictured under an argon atmosphere. Gray arsenic, also called grey arsenic or metallic arsenic, is the most stable allotrope of the element at room temperature, and as such is its most common form. [1] This soft, brittle allotrope of arsenic has a steel gray, metallic color, and is a good conductor. [2]
It began to fall out of favor after the 1860s because of its toxicity and the instability of its color in the presence of sulfides and various chemical pollutants. [5] The acutely toxic nature of Scheele's green as well as other arsenic-containing green pigments such as Paris green may have contributed to the sharp decline in the popularity of ...