por The halide salts They are binary compounds formed by a metal and a non-metal, without any other type of element. These salts are formed by the neutralization reaction between a hydroacid acid with a base. For example: the reaction between hydrochloric acid (HCl) with sodium hydroxide (NaOH) to form sodium chloride (NaCl).
Halide salts are also formed by the reaction of a hydracid with a metal. For example: the reaction of magnesium with hydrochloric acid to form magnesium chloride (MgCl2). As can be seen, chlorides are the most representative halide salts. However, they are not the only ones.
Halide salts, according to some definitions, include compounds that contain halogens in their structure; that is to say: fluorine, chlorine, bromine and iodine, which is why they are considered synonymous with halides or halides.
Likewise, within the halide salts are included, by some authors, compounds formed by the union of a metal with an element that is using its negative valence, among them: carbides, nitrides, phosphides, sulfides, selenides, arsenides, etc. These also count as halide salts as long as they consist of only two elements.
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Properties of halide salts
Halide salts are a group of compounds whose properties are difficult to establish.
strong ionic bonds
In general, they consist of solids with strong ionic bonds between ions of two elements: M+X–, where M+ corresponds to the metal cation, and X– the anion derived from the nonmetal.
High melting, boiling and sublimation points
They tend to have very high melting, boiling and sublimation points, precisely due to the strength of their crystalline structure.
conduction of electricity
In the solid state they are poor conductors of electricity, but in aqueous solution, when they ionize, or when they melt, they become good conductors.
Appearance
They are crystalline solids that, when fragmented into powder, can turn white. However, many halide salts can have a different coloration. For example, nickel chloride is green in color, while ferric chloride fluctuates between green and red.
Solubility
Most halide salts are soluble in water, with the exception of silver, lead(II), and mercury(I) halides.
Smell
Because they are not volatile compounds, halide salts do not have strong odors. Also, due to their composition, they can have sour, salty, bitter or sweet flavors.
Nomenclature
Halide salts are named by placing the name of the anion with the suffix aurochs, followed by the name of the metal directly, preceded by the conjunction of. In the event that the metal has more than one valence, the metal is placed with the suffix bear o ico, depending on its valence.
The name of the metal can also be placed without a suffix and with the oxidation number in parentheses.
For example: iron (III) chloride, or ferric chloride, FeCl3.
How are halide salts formed?
Halide salts are formed mainly by three reactions: neutralization, reaction of an acid with a metal, and the reaction of a metal with a metalloid or a nonmetal acting with a negative valence.
neutralization reaction
It is the reaction of an acid with a base, producing salt and a water molecule. For example:
HCl + NaOH → NaCl + H2O
This example was mentioned at the beginning.
Reaction of an acid with a metal
A strong acid can react with a metal, forming a salt and the release of hydrogen (H2). For example: hydrochloric acid reacts with zinc (Zn) to form zinc chloride (ZnCl2):
Zn + HCl → ZnCl2 + H2
Combination of a metal with a metalloid or a nonmetal
These halide salts result from the combination of a metal with a metalloid or a non-metal other than the halogens. For example: in aluminum phosphide, phosphorus with valence -3 are combined with aluminum with valence +3. However, said «combination» is due to specific production reactions for each salt.
Uses/applications
metal halides
Metal halides are used in high intensity lamps, such as modern lamps. They are also used in greenhouses or in rainy climates to supplement natural light. Silver halides are used in films and photographic papers.
Calcium chloride
Calcium chloride is used as a source of calcium in wastewater treatment. Likewise, it is used as a source of calcium through its electrolysis. It is used in the treatment of cardiac arrhythmias and in cases of severe hypocalcemia.
Ferric chloride
Ferric chloride is used in the treatment of wastewater and in the purification of water. It is also used to record or pickle copper and is involved as a catalyst in the vinyl chloride synthesis process.
Potassium Chloride and Bromide
Potassium chloride is used as a fertilizer and in the treatment of hypokalemia or hypokalemia. Potassium bromide, on the other hand, was used as an anticonvulsant, and is currently used in the pharmaceutical industry and as a dressing.
Sodium chloride and sulfide
Sodium chloride is used as a food flavoring, in meat preservation, as an antiseptic, in severe hyponatremia, etc. Sodium sulfide is used in nuclear reactors in the production of heavy water, in removing hair from hides, and in the manufacture of rubber, dyes, and paints.
phosphides and nitrides
Aluminum phosphide is used as a broadband semiconductor and as an insecticide. Meanwhile, gallium nitride is used as a semiconductor.
Examples of halide salts
Apart from the examples mentioned in the previous section, other halide salts with their respective formulas and names will be listed below:
-NaCl: sodium chloride
-KCl: potassium chloride
-CaCl2: calcium chloride
-MgCl2: Magnesium chloride
-CsCl: Cesium Chloride
-BaCl2: barium chloride
-FeCl2: Ferrous chloride
-FeCl3: ferric chloride
-NiCl2: Nickel chloride
-CuCl: Cuprous chloride
-CuCl2: Cupric chloride
-AgCl: silver chloride
-ZnCl2: Zinc chloride
-CdCl2: cadmium chloride
-HgCl2: Mercuric chloride
-AlCl3: Aluminum chloride
-NaBr: Sodium bromide
-KBr: potassium bromide
-CsBr: Cesium bromide
-CdBr: cadmium bromide
-MgBr2: Magnesium bromide
-SrBr2: Strontium(II) bromide
-KI: potassium iodide
-NaI: sodium iodide
-CsI: cesium iodide
-AlI3: aluminum iodide
-PbI2: Lead(II) iodide
-NaF: Sodium fluoride
-LiF: Lithium Fluoride
-CaF2: Calcium fluoride
-PtF2: Platinum(II) fluoride
-NaS2: Sodium sulfide
-Li4C: Lithium carbide
-Mg2C: Magnesium carbide
-AlP: Aluminum phosphide
-Si3N4: Silicon nitride
-TiN: Titanium nitride
References
Shiver & Atkins. (2008). Inorganic chemistry. (fourth edition). Mc Graw Hill.
Whitten, Davis, Peck & Stanley. (2008). Chemistry. (8th ed.). CENGAGE Learning.
Julian Perez Porto and Maria Merino. (2016). Definition of halide salts. Definition of. Recovered from: definition.de
James P. Birk. (June 5, 2019). Halide ions. Chemistry LibreTexts. Retrieved from: chem.libretexts.org
Wikipedia. (2020). Halide. Retrieved from: en.wikipedia.org