chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, proper ...

, a halide (rarely halogenide) is a binary chemical compound, of which one part is a

halogen The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the modern IUPAC nomenclature, this grou ...

atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, a ...

and the other part is an element or

radical Radical may refer to: Politics and ideology Politics * Radical politics, the political intent of fundamental societal change *Radicalism (historical), the Radical Movement that began in late 18th century Britain and spread to continental Europe an ...

that is less

electronegative Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...

(or more electropositive) than the halogen, to make a

fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts ty ...

chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride s ...

, 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

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

s are halides; the ''hal-'' syllable in ''halide'' and ''

halite Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, p ...

'' reflects this correlation. All Group 1 metals form halides that are white solids at room temperature. A halide ion is a halogen atom bearing a negative charge. The halide

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

s are

(),

(), bromide (), iodide () and astatide (). Such ions are present in all ionic halide salts.

Halide mineral Halide minerals are those minerals with a dominant halide anion (, , and ). Complex halide minerals may also have polyatomic anions. Examples include the following: * Atacamite *Avogadrite (K,Cs)BF * Bararite (β) * Bischofite * Brüggenit ...

s contain halides. All these halides are colourless, high melting crystalline solids having high negative enthalpies of formation.

Tests

Halide compounds such as , and can be tested with

silver nitrate Silver nitrate is an inorganic compound with chemical formula . It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called ''lunar causti ...

solution, . The halogen will react with and form a precipitate, with varying colour depending on the halogen: * : no precipitate can solve in water. * : white * : creamy (pale yellow) * : green (yellow) For organic compounds containing halides, the Beilstein test is used.

Uses

Metal halides are used in high-intensity discharge lamps called metal halide lamps, such as those used in modern

street light A street light, light pole, lamp pole, lamppost, street lamp, light standard, or lamp standard is a raised source of light on the edge of a road or path. Similar lights may be found on a railway platform. When urban electric power distribution ...

s. 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

greenhouse A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of transparent material, such as glass, in which plants requiring regulated climatic conditions are grown.These ...

s or in rainy climates to supplement natural

sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when ...

Silver halide A silver halide (or silver salt) is one of the chemical compounds that can form between the Chemical element, element silver (Ag) and one of the halogens. In particular, bromine (Br), chlorine (Cl), iodine (I) and fluorine (F) may each combine wi ...

s are used in

photographic film Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the crystals determine ...

s 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 Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J ...

often incorporates halogens into organohalide compounds.

Compounds

Examples of halide compounds are: *

Sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35. ...

(NaCl) *

Potassium chloride Potassium chloride (KCl, or potassium salt) is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water, and its solutions have a salt ...

(KCl) * Potassium iodide (KI) * Lithium chloride (LiCl) *

Copper(II) chloride Copper(II) chloride is the chemical compound with the chemical formula CuCl2. The anhydrous form is yellowish brown but slowly absorbs moisture to form a blue-green dihydrate. Both the anhydrous and the dihydrate forms occur naturally as the ve ...

() *

Silver chloride Silver chloride is a chemical compound with the chemical formula Ag Cl. This white crystalline solid is well known for its low solubility in water (this behavior being reminiscent of the chlorides of Tl+ and Pb2+). Upon illumination or heat ...

(AgCl) *

Calcium chloride Calcium chloride is an inorganic compound, a salt with the chemical formula . It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with calcium hydroxide. Ca ...

() *

Chlorine fluoride A chlorine fluoride is an interhalogen compound containing only chlorine and fluorine. {, class="wikitable" , - ! ! ClF ! ClF3 ! ClF5 , - , Systematic name , Chlorine monofluoride , Chlorine trifluoride , Chlorine pentafluoride , - , ...

(ClF) * Organohalides **

Bromomethane Bromomethane, commonly known as methyl bromide, is an organobromine compound with formula C H3 Br. This colorless, odorless, nonflammable gas is produced both industrially and biologically. It has a tetrahedral shape and it is a recognized ozo ...

() ** Iodoform () *

Hydrogen chloride The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chlorid ...

(HCl) *

Hydrogen bromide Hydrogen bromide is the inorganic compound with the formula . It is a hydrogen halide consisting of hydrogen and bromine. A colorless gas, it dissolves in water, forming hydrobromic acid, which is saturated at 68.85% HBr by weight at room tem ...

(HBr)

Silicon

* SiF₄ (a gas) * SiCl₄ * SiB''r''₄ * SiI₄ * SiAt₄ * SiTs₄

References

{{Authority control Salts

Tests

Uses

Compounds

Silicon

See also

References