Arsenic
Phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi) form a group of four elements in Group 5A of the periodic table. They exhibit increasing metallic properties going down the group. Nitrogen (N), which heads the group, is a colorless, odorless, and tasteless gas. Phosphorus is a highly reactive nonmetal, arsenic and antimony are poisonous metalloids, and bismuth is a true metal. Because of the arrangement of the outer electrons in their atoms, each of these elements can form up to five chemical bonds with other elements or groups of elements. Arsenic has an atomic number 33, atomic mass is 74.9216, and it sublimes (passes directly into a vapor without melting) at 613° C. The Earth's crust contains relatively little arsenic, only about 5.5 parts per million. Arsenic and some arsenic compounds have been known for a long time. Aristotle thought that arsenic was a kind of sulfur. The Latin word arsenicum means yellow orpiment (a pigment containing arsenic and sulfur). While knowledge of arsenic dates back to ancient Greece, it wasn't until the Middle Ages that its poisonous characteristics were described. It was identified by Albert Magnus about 1250, and he described the way
Due to this, and to its being carcinogenic, but also because of the toxicity of arsenic and its compounds in general, environmental regulation is expected to become increasingly stringent. While this might adversely affect arsenic demand in the long term, it should only have a minor near-time effect. Arsenic is very similar to antimony and bismuth. It exists in bright, metallic forms that are stable in air. It is found free in nature or in combination with other elements, usually sulfur. It is most often used to improve the strength and hardness of alloys, which are combinations of metals. Arsenic is a gray, shiny metalloid, which is a moderately good conductor of heat and electricity, but gray arsenic is brittle and breaks easily. This is the ordinary, stable form of the element. There are two other allotropes (solid forms)--yellow arsenic and black arsenic, whose modifications have no metallic properties. Occasionally found free in nature, arsenic usually occurs in combination with sulfur, oxygen or certain metals like cobalt, copper, nickel, iron, silver, and tin. In combination, such arsenic is referred to as inorganic arsenic. Arsenic combined with carbon and hydrogen is referred to as organic arsenic. The organic forms are usually less toxic than inorganic forms. The principal arsenic-containing mineral is arsenopyrite. The most widely used arsenic compound is white arsenic, also called arsenic trioxide. It is usually produces as a by-product of the smelting (melting)of copper or lead. At about 400° C it burns with a bluish flame, forming the As2O3 (arsenic trioxide), which is used as a rat poison. In water, arsenic combinations range from being quite soluble (sodium arsenite and arsenic acid) to practically insoluble (arsenic trisulfide). Twenty-one arsenic compounds are considered to be of concern because of their toxicity and/or presence in the environment.
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Approximate Word count = 1343
Approximate Pages = 5 (250 words per page double spaced)
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