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Iodide

Iodide
I-.svg
Iodide ion.svg
Names
Systematic IUPAC name
Iodide
Identifiers
20461-54-5 YesY
3D model (Jmol) Interactive image
3587184
ChEBI CHEBI:16382
ChEMBL ChEMBL185537 YesY
ChemSpider 28015 YesY
ECHA InfoCard 100.125.457
14912
KEGG C00708 YesY
PubChem 30165
Properties
I
Molar mass 126.90 g·mol−1
Thermochemistry
169.26 J K−1 mol−1
Related compounds
Other anions
Fluoride

Chloride
Bromide

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Chloride
Bromide

An iodide ion is the ion I. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts, not organoiodine compounds. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine deficiency affects two billion people and is the leading preventable cause of intellectual disability.

Iodide is one of the largest monatomic anions. It is assigned a radius of around 206 picometers. For comparison, the lighter halides are considerably smaller: bromide (196 pm), chloride (181 pm), and fluoride (133 pm). In part because of its size, iodide forms relatively weak bonds with most elements.

Most iodide salts are soluble in water, but often less so than the related chlorides and bromides. Iodide, being large, is less hydrophilic compared to the smaller anions. One consequence of this is that sodium iodide is highly soluble in acetone, whereas sodium chloride is not. The low solubility of silver iodide and lead iodide reflects the covalent character of these metal iodides. A test for the presence of iodide ions is the formation of yellow precipitates of these compounds upon treatment of a solution of silver nitrate or lead(II) nitrate.

Aqueous solutions of iodide salts dissolve iodine better than pure water. This effect is due to the formation of the triiodide ion, which is brown:

Iodide salts are mild reducing agents and many react with oxygen to give iodine. A reducing agent is a chemical term for an antioxidant. Its antioxidant properties can be expressed quantitatively as a redox potential :


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