Halide

 ( Salts ) 

In chemistry, a halide (rarely halogenide) is a Binary phase, of which one part is a halogen atom and the other part is an chemical element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluoride, chloride, bromide, iodide, astatide, or theoretically tennesside compound. The alkali metals combine directly with halogens under appropriate conditions forming halides of the general formula, MX (X = F, Cl, Br or I). Many salts are halides; the hal- syllable in halide and halite reflects this correlation.

A halide ion is a halogen atom bearing a negative charge. The common halide are fluoride (), chloride (), bromide (), and iodide (). Such ions are present in many ionic bonding halide salts. contain halides. All these halide anions are colorless. Halides also form covalent bonds, examples being colorless TiF₄, colorless TiCl₄, orange TiBr₄, and brown TiI₄. The heavier members TiCl₄, TiBr₄, TiI₄ can be distilled readily because they are molecular. The outlier is TiF₄, melting point, because it has a polymeric structure. Fluorides often differ from the heavier halides.

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Reactions

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Redox Halides cannot be reduced under the usual laboratory conditions, but they all can be oxidized to the parent halogens, which are diatomic. Especially for iodide and less so for the lighter halides, intermediates can be observed and isolated. Best characterized is triiodide. Many related species are known, including a host of .

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Protonation Halides are conjugate bases of , which are all gases. When the protonation is conducted in aqueous solution, are produced.

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Reaction with silver ions Halide salts such as , and Potassium iodide are highly soluble in water to give colorless solutions. The solutions react readily with a solution of silver nitrate . These three halides form solid :

• Silver chloride: white
• Silver bromide: pale yellow
• Silver iodide: yellow

Similar but slower reactions occur with in place of alkali metal halides, as described in the Beilstein test.

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Uses Metal halides are used in high-intensity discharge lamps called metal halide lamps, such as those used in modern . These are more energy-efficient than mercury-vapor lamps, and have much better colour rendition than orange high-pressure sodium lamps. Metal halide lamps are also commonly used in or in rainy climates to supplement natural sunlight.

are used in photographic films and papers. When the film is developed, the silver halides which have been exposed to light are reduced to metallic silver, forming an image.

Halides are also used in solder paste, commonly as a Cl or Br equivalent.

Synthetic organic chemistry often incorporates halogens into organohalide compounds.

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See also

• Salinity
• Organohalide
• Hydrogen halide
• Silver halide

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