Halide

For the name, see Halide (name).

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 (or more electropositive) than the halogen, to make a fluoride, chloride, bromide, iodide, or astatide compound. Many salts are halides. All Group 1 metals form halides which are white solids at room temperature.

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.

See chloride, bromide, fluoride, and iodide

Tests

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 varying colour depending on the halogen:

• AgF: No Precipitate
• AgCl: White
• AgBr: Creamy (Pale Yellow)
• AgI: 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 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.

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

Compounds

Examples of halide compounds are:

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

See also

• Salinity
• Organohalide
• Hydrogen halide