halogen


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halogen

(hăl`əjĕn) [Gr.,=salt-bearing], any of the chemically active elements found in Group 17 of the periodic tableperiodic table,
chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled
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; the name applies especially to fluorinefluorine
, gaseous chemical element; symbol F; at. no. 9; at. wt. 18.9984; m.p. −219.6°C;; b.p. −188.14°C;; density 1.696 grams per liter at STP; valence −1. Fluorine is a yellowish, poisonous, highly corrosive gas.
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 (symbol F), chlorinechlorine
[Gr.,=green], gaseous chemical element; symbol Cl; at. no. 17; interval in which at. wt. ranges 35.446–35.457; m.p. −100.98°C;; b.p. −34.6°C;; density 3.2 grams per liter at STP; valence −1, +1, +3, +5, +7.
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 (Cl), brominebromine
[Gr.,=stench], volatile, liquid chemical element; symbol Br; at. no. 35; at. wt. 79.904; m.p. –7.2°C;; b.p. 58.78°C;; sp. gr. of liquid 3.12 at 20°C;; density of vapor 7.14 grams per liter at STP; valence −1, +1, +3, +5, or +7.
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 (Br), and iodineiodine
[Gr.,=violet], nonmetallic chemical element; symbol I; at. no. 53; at. wt. 126.90447; m.p. 113.5°C;; b.p. 184.35°C;; sp. gr. 4.93 at 20°C;; valence −1, +1, +3, +5, or +7.
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 (I). Astatineastatine
[Gr.,=unstable], semimetallic radioactive chemical element; symbol At; at. no. 85; at. wt. of most stable isotope 210; m.p. 302°C; (estimated); b.p. 337°C; (estimated); density unknown; valence believed to be +1, +3, +5, or +7.
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 (At), formerly known as alabamine, is a radioactive element also classed as a halogen; its most stable isotope (which does not occur in nature) has a half-life of less than 8 1-2 hr. The chemical and physical properties of astatine are not well known; it is believed to resemble iodine. The halogens are the best-defined family of chemical elements. Chemically they closely resemble one another; they are nonmetallic and form monovalent negative ions. They also exhibit an almost perfect gradation of physical properties. Fluorine, a pale yellow gas, is the least dense and chemically the most active, displacing the other halogens from their compounds and even displacing oxygen from water. Chlorine, a yellow-green gas, is more dense and less reactive than fluorine. Bromine is a dark red liquid. Iodine is a grayish black solid and is the least chemically active of the four; however, among the nonmetals only oxygen is more reactive than iodine. Pure halogens exist as diatomic molecules, e.g., Cl2; they form interhalogen compounds, i.e., compounds between two halogens. The halogens form numerous compounds with other elements. With hydrogen they form hydrogen halides, whose water solutions are called hydrohalic acids, e.g., the water solution of hydrogen chloridehydrogen chloride,
chemical compound, HCl, a colorless, poisonous gas with an unpleasant, acrid odor. It is very soluble in water and readily soluble in alcohol and ether. It fumes in moist air. It is not flammable, and the liquid is a poor conductor of electricity.
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 is called hydrochloric acid. They form numerous metal halides, or saltssalt,
chemical compound (other than water) formed by a chemical reaction between an acid and a base (see acids and bases). Characteristics and Classification of Salts

The most familiar salt is sodium chloride, the principal component of common table salt.
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, e.g., sodium chloride, common table salt. They also form halocarbons, compounds with carbon and often other elements such as hydrogen and oxygen. Chloroformchloroform
or trichloromethane
, CHCl3, volatile, colorless, nonflammable liquid that has a sweetish taste and a somewhat pungent odor; it boils at 61.7°C;. It dissolves freely in ethanol and ether but does not mix with water.
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, iodoformiodoform
, CHI3, yellow crystalline solid that has a penetrating odor. It melts at 119°C; and is insoluble in water but soluble in ether or ethanol. Iodoform was formerly used as an antiseptic.
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, and carbon tetrachloridecarbon tetrachloride
or tetrachloromethane
, CCl4, colorless, poisonous, liquid organic compound that boils at 76.8°C;. It is toxic when absorbed through the skin or when inhaled. It reacts at high temperatures to form the poisonous gas phosgene.
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 are halocarbons. Some other halogen compounds are calomel (mercurous chloride), fluoritefluorite
or fluorspar
, mineral appearing in various colors, e.g., green, yellow-brown, rose, and red. Chemically, it is calcium fluoride, CaF2. Its crystals, commonly cubic, are transparent or translucent and under certain conditions exhibit fluorescence.
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, sal ammoniac (ammonium chlorideammonium chloride
, chemical compound, NH4Cl, a white or colorless, odorless, water-soluble, cubic crystalline salt with a biting taste, commonly known as sal ammoniac.
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), corrosive sublimate (mercuric chloridemercuric chloride
or mercury (II) chloride,
chemical compound, HgCl2, a white powder of colorless rhombohedral crystals, somewhat soluble in water. It is also called bichloride of mercury or corrosive sublimate. It is extremely poisonous.
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), and chlorine bleaches.
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Halogen

A type of incandescent lamp with a higher energy efficiency than standard ones.
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved

halogen

[′hal·ə·jən]
(chemistry)
Any of the elements of the halogen family, consisting of fluorine, chlorine, bromine, iodine, and astatine.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

halogen

any of the chemical elements fluorine, chlorine, bromine, iodine, and astatine. They are all monovalent and readily form negative ions
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
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Group Managing Director of Halogen Security Company Limited, Mr.
Under the deal, Saba and Vector acquired Halogen for CDN 12.50 in cash per share, implying an aggregate fully-diluted equity value for halogen of approximately CDN 293m (USD 223.56m).
Price The thing that tends to put people off buying an LED bulb is the upfront cost in comparison to a halogen bulb.
The majority of halogen bonds that we know are based on halogen atom due to the presence of a very small area with positive electrical potential.
And while all of the LED products tested were more efficacious than the halogen benchmarks, the range in efficacy was quite large (38-90 lumens per watt).
The traditional circuit design used on airfields around the globe consists of circuits powered by constant current regulators (CCRs) providing 6.6A at a generally high level of output voltage into a circuit using standard 6.0mm2 cables connected via a series isolating transformer in the range 30 to 300W which are sized to suit the power requirement of the tungsten halogen lamp used to produce the requisite photometric output.
Low Smoke Zero Halogen (LSZH) Loose Tube cable are located within S-Z stranded buffer tubes, which provide stable and reliable long-term performance.
Using a jet cooled molecular beam, combined with the Fourier-transform microwave spectroscopy, Legon has investigated the geometry and the stability of some halogen bonding complexes in the gas phase through the analysis of their rotational spectra [22, 23].
The Sun Brite 5-Watt MR-16 Retrofit LED from Lumex is said to provide significant cost and performance benefits compared to halogen alternatives.
Ocean Optics' Vivo NIR Source is a compact, tungsten halogen light source for Vis-NIR spectroscopy across the 360 to 2000 nm range.
This revolutionary oven uses halogen and infrared technology with a fan assist function to cook food faster than a conventional oven.