halogen

any of five related nonmetallic elements (fluorine or chlorine or bromine or iodine or astatine) that are all monovalent and readily form negative ions

This article discusses the group of chemical elements in the periodic table:for the light bulb, see !Halogen_lamp#The_halogen_lamp< bara>the halogen lamp.'' The halogens are a chemical series. They are the chemical elementelements in Periodic table groupGroup 17 (old-style: VII or VIIA) of the periodic table: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At) and the as yet undiscovered ununseptium (Uus). The word halogen was coined to mean elements which produce salt in union with a metal. It comes from 18th c. scientific French nomenclature based on erring adaptations of Greek languageGreek roots. These elements are diatomic molecules in their natural form. They require one more electron to fill their outer electron shellelectron shells, and so have a tendency to form a singly-charged negative ion. This negative ion is referred to as a ''halide'' ion; saltsalts containing these ions are known as halidehalides.Halogens are highly reactivityreactive, and as such can be harmful or lethal to biological organisms in sufficient quantities. Chlorine and iodine are both used as disinfectants for such things as drinking water, swimming pools, fresh wounds, dishes, and surfaces. They kill bacteria and other potentially harmful microorganisms, a process known as sterilization. Their reactive properties are also put to use in Bleaching agentbleaching. Chlorine is the active ingredient of most Clothfabric bleaches and is used in the production of most paper products.Halide ions combined with single hydrogen atoms form the hydrohalic acid''hydrohalic'' acids (i.e., HF, HCl, HBr, HI), a series of particularly strong acids. (HAt, or "hydrastatic acid", should also qualify, but it is not typically included in discussions of hydrohalic acid due to astatine's extreme instability toward alpha decay.)They react with each other to form interhalogen compounds. Diatomic interhalogen compounds (BrF, ICl, ClF, etc.) bear strong superficial resemblance to the pure halogens.Many synthetic organic compounds such as plastic polymers, and a few natural ones, contain halogen atoms; these are known as ''halogenated'' compounds or organic halides. Chlorine is by far the most abundant of the halogens, and the only one needed in relatively large amounts (as chloride ions) by humans. For example, chloride ions play a key role in brain function by mediating the action of the inhibitory transmitter GABA and are also used by the body to produce stomach acid. Iodine is needed in trace amounts for the production of thyroid hormones such as thyroxine. On the other hand, neither fluorine nor bromine are believed to be really essential for humans, although small amounts of fluoride can make tooth enamel resistant to decay.They show a number of trends when moving down the group - for instance, decreasing electronegativity and reactivity, increasing melting and boiling point.? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? !?

Halogen< ;/td>?	&l t;b>Atomic? Mass	&l t;b>Melting? Point	&l t;b>Boiling? Point	&l t;b>Electronegativity
Fluorine	19	53 .53	85 .03	3. 98
?	35 .5	17 1.6	23 9.11	3. 16
Bromine	80	26 5.8	33 2.0	2. 96
?	12 7	39 6.85	45 7.4	2. 66
Astatine	21 0	57 5	61 0	2. 2
Ununseptium29 1*	*& lt;/td>?	*& lt;/td>?	*& lt;/td>? !

*? Ununseptium has not yet been discovered; values are either unknown if no value appears, or are estimates based on other similar chemicals.

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PeriodicTablesFoote r?


See also -

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Since its foundation 1991, TRANSTEC Elektroanlagen GmbH stands for highest quality at development and production of electrotechnical components with an emphasis on manufacturing toroidal transformers. During the first five years of its existance, TRANSTEC established itself as an outstanding producer for the low-voltage halogen lighting industry. The many decades encompassing experience of its staff members enabled the enterprise to continuously evolve into today’s well-known transformer specialist. The steady growing customer base includes many well-known companies out of the power supply-, medical equipment-, audio-, and solar-industries, as well as customers from a variety of other industrial areas. Professional competence, highest flexibility and quality have brought forth that in the 21st century TRANSTEC is being consulted by its clients far beyond the development of transformers also for the compilation, development and manufacturing of customized electrotechnical components.
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Benshine Inc. A World In Lights
Manufacturer of miniature and subminiature incandescent lamps (bulbs) including Xenon , Halogen and Krypton . Specializing in direct OEM supply . Accredited quality system assures top quality and lowest prices .
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Independent Testing Laboratories, Inc.
Independent Testing Laboratories, Inc. (ITL) Boulder, CO. Serving the lighting industry- Photometric and Electrical testing, AutoLux Lighting Software, Reflector Design, Lighting Photometry Application Engineering, ITL Goniophotometer systems, ITL photometry, ITL IES files
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Halogen Software
Web-based e-survey and feedback software plus design, support, analysis and training services. Product, news, support, profile and contact information.
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Halogen Records
Independent record label based in Vermont. Artists include Dezert Eez, Thornwheel Steady and Planet X. Catalog, audio and links.
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