halide

halide: see halogen.

A halide is a binary compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative than the halogen, to make a fluoride, chloride, bromide, iodide, or astatide compound. Many salts are halides. All Group 1 metals form halides with the halogens and they are white solids.

A halide ion is a halogen atom bearing a negative charge. The halide anions are fluoride (F⁻), chloride (Cl⁻), bromide (Br⁻), iodide (I⁻) and astatide (At⁻). Such ions are present in all ionic halide salts.

Halides in organic chemistry

In organic chemistry halides represent a functional group. Any organic compound that contains a halogen atom can be considered a halide. Alkyl halides are organic compounds of the type R-X, containing an alkyl group R covalently bonded to a halogen X.

Pseudohalides resemble halides in their charge and reactivity; common examples are azides NNN-, isocyanate -NCO, Isocyanide, CN-, etc. (See also: pseudohalogen.)

A chemical test for the detection of halogen in chemical substances is the Carius halogen method.

Dihalides are commonly used in the synthesis of cyclic alkanes.

Test for Halide ions

Halide compounds such as KCl, KBr and KI can be tested with silver nitrate solution, AgNO₃. The halogen will react with Ag⁺ and form a precipitate, with colour as follow:
AgF - Yellowish Brown
AgCl - White
AgBr - Creamy (Pale Yellow)
AgI - Yellow

Halides in lighting

Metal halides are used in high-intensity discharge lamps called metal halide lamps, such as those used in modern street lights. 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 greenhouses or in rainy climates to supplement natural sunlight.

HID (High-intensity discharge) lamps however, contribute highly to light pollution. Sodium-vapor are favored for this reason.

Halide compounds

Examples of halide compounds are:

• sodium chloride (NaCl)
• potassium chloride (KCl)
• potassium iodide (KI)
• lithium chloride (LiCl)
• copper(II) chloride (CuCl₂)
• chlorine fluoride (ClF)
• Bromomethane (CH₃Br)
• Iodoform (CHI₃)
• silver chloride (AgCl)

See also

• Salinity
• Functional groups

References