Halogen family elements

Astatine is a member of the halogen family, elements in Group 17 (VlIA) of the periodic table. It is one of the rarest elements in the universe. Scientists believe that no more than 25 grams exist on Earth s surface. All isotopes of astatine are radioactive and decay into other elements. For this reason, the element s properties are difficult to study. What is known is that it has properties similar to those of the other halogens—fluorine, chlorine, bromine, and iodine. Because it is so rare, it has essentially... 

Iodine [7553-56-2] I, atomic number 53, atomic weight 126.9044, is a nonmetaUic element belonging to the halogen family in Group 17 (VIIA) of the Periodic Table. The only stable isotope has a mass number of 127. There are 22 other iodine isotopes having masses between 117 and 139 14 of these isotopes yield significant radiation. 

Elemental fluorine, which is a member of the halogen family, is a pale yellow-green, irritating gas with a sharp odour and atomic mass of 18.998. Fluorine is chemically most reactive of all the elements and does not therefore occur naturally in the free state. In combination it comprises 0.065% of the earth s crust, being the 13th element in abundance [1], and is an inevitable part of the biosphere and human life. The term fluorine is, in this report, used to denote the element in any of its forms and fluoride to denote free inorganic fluoride to which a fluoride ion-selective electrode (ISE) responds. 

This section summarizes the chemical and physical properties which are shared in some degree by all of the nonmetallic elements, and the following sections briefly delineate the chemistry of several additional nonmetallic elements—carbon, silicon, nitrogen, phosphorus, and sulfur. A later section discusses the properties of the elements of the halogen family. 

All the elements of the halogen family except astatine occur in nature in the form of their compounds. Because of their marked chemical activity, they are never found in nature in the uncombined state. 

A review of the means whereby the elements of the halogen family may be prepared either in the laboratory or on an industrial scale provides further insight into the interrelationships of these elements. 

Chlorine is by far the most useful of the elements of the halogen family. This fact becomes evident when one learns that the annual production of chlorine in the United States alone amounts to approximately 250,000 tons. Much of this chlorine is used in the bleaching of fabrics, wood pulp, and so forth. Considerable quantities of this element are used in treating water supplies for the purpose of destroying harmful bacteria. Many of the poisonous gases used in the world wars were chlorine compounds, such as mustard gas [(C1C2H4)2S], chloropicrin... 

In 1940, Corson, Mackenzie, and Segre announced the production of an isotope of element 85, astatine (At), which is the last member of the halogen family. This synthesis involved bombardment of bismuth with alpha particles in a cyclotron ... 

Iodine is the heaviest of the halogen family of elements, excluding the radioactive element astatine. It was discovered in 1811 by French chemist Bernard Courtois, who isolated the element from seaweed. The element is named for its color in the gas phase (the Greek word iodes means violet ). 

Halogen family—Group of elements in the periodic table consisting of fluorine, chlorine, bromine, iodine, and astatine. 

---