Iodide

Ion, and compounds containing the ion

Not to be confused with iodine.

"i-" redirects here. For the Internet-related prefix i-, see Wiktionary's entry i-.

Iodide  |  |

|

Names
Systematic IUPAC name

Iodide[1]

Identifiers

CAS Number

* 20461-54-5 Y

3D model (JSmol)

* Interactive image

Beilstein Reference

| 3587184
ChEBI |

* CHEBI:16382

ChEMBL |

* ChEMBL185537 Y

ChemSpider |

* 28015 Y

Gmelin Reference

| 14912
KEGG |

* C00708 Y

PubChem CID

* 30165

UNII |

* 09G4I6V86Q Y

InChI

* InChI=1S/HI/h1H/p-1 Y

Key: XMBWDFGMSWQBCA-UHFFFAOYSA-M Y

SMILES

* [I-]

Properties

Chemical formula

| I−

Molar mass | 126.90447 g·mol−1
Conjugate acid | Hydrogen iodide
Thermochemistry

Std molar
entropy (S⦵298)

| 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

Chemical compound

An iodide ion is I−.[2] Compounds with iodine in formal oxidation state −1 are called iodides. 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.[3]

## Structure and characteristics of inorganic iodides

[edit]

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.[2]

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:

I− \+ I2 ⇌ I−

### Redox, including antioxidant properties

[edit]

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:

2I− ⇌  I2 \+ 2e− E° = 0.54 volts (versus SHE)

Because iodide is easily oxidized, some enzymes readily convert it into electrophilic iodinating agents, as required for the biosynthesis of myriad iodide-containing natural products. Iodide can function as an antioxidant reducing species that can destroy ozone[4] and reactive oxygen species such as hydrogen peroxide:[5]

2 I− \+ peroxidase \+ H2O2 \+ tyrosine, histidine, lipid, etc. → iodo-compounds + H2O + 2 e−

## Representative iodides

[edit]

Compound  | Formula  | Appearance  | Use or occurrence

|
|
|

Potassium iodide | KI  | white crystals  | iodine component of iodized salt
Hydrogen iodide | HI  | colourless gas  | strong mineral acid
Silver iodide | AgI  | yellow powder that darkens in light  | photoactive component of silver-based photographic film
Thyroxine
(3,5,3′,5′-tetraiodothyronine)  | C15H11I4NO4 | pale yellow solid  | hormone essential for human health

## Natural occurrence

[edit]

Iodargyrite—natural, crystalline silver iodide—is the most common iodide mineral currently known. Iodide anions may sometimes also be found combined with mercury, copper and lead, but minerals with such compositions are even more scarce.[6]

## Other oxoanions

[edit]

Iodine can assume oxidation states of −1, +1, +3, +5, or +7. A number of neutral iodine oxides are also known.

Iodine oxidation state  | −1  | +1  | +3  | +5  | +7

|
|
|
|
|

Name  | iodide | hypoiodite | iodite | iodate | periodate
Formula  | I− | IO− | IO−
2 | IO−
3 | IO−
4 or IO5−

## References

[edit]

1. ^ "Iodide - PubChem Public Chemical Database". The PubChem Project. USA: National Center for Biotechnology Information.
2. ^ a b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
3. ^ McNeil, Donald G. Jr (2006-12-16). "In Raising the World's I.Q., the Secret's in the Salt". New York Times. Retrieved 2008-12-04.
4. ^ Pillar, Elizabeth A.; Guzman, Marcelo I.; Rodriguez, Jose M. (2013-10-01). "Conversion of Iodide to Hypoiodous Acid and Iodine in Aqueous Microdroplets Exposed to Ozone". Environmental Science & Technology. 47 (19): 10971–10979\. Bibcode:2013EnST...4710971P. doi:10.1021/es401700h. ISSN 0013-936X. PMID 23987087.
5. ^ Küpper FC; Carpenter LJ; McFiggans GB; et al. (2008). "Iodide accumulation provides kelp with an inorganic antioxidant impacting atmospheric chemistry" (Free full text). Proceedings of the National Academy of Sciences of the United States of America. 105 (19): 6954–8\. Bibcode:2008PNAS..105.6954K. doi:10.1073/pnas.0709959105. PMC 2383960. PMID 18458346.
6. ^ "Mineral/rock/commodity names containing 'iodide'". mindat.org. Retrieved 2022-08-09.

## External links

[edit]

* "Seaweed use iodine as an antioxidant". Chemistry World blog. Archived from the original on 2010-07-03. Retrieved 2008-05-15.
* "Stressed seaweed contributes to cloudy coastal skies, study suggests". Retrieved 2008-05-15.

* v
* t
* e

Iodine compounds

Iodine(−I)|

* HI
* NiI2−4
* AtI
* other

Iodine(I)|

* I2O
* HIO
* IN3
* ICN
* ICl
* IF
* NI3
* IBr
* INO3
* C3H5I

Iodine(II)|

* IO

Iodine(III)|

* HIO2
* ICl3
* IF3
* IBr3
* (IO)2SO4
* I2(SO4)3

Iodine(IV)|

* IO

Iodine(V)|

* HIO3
* IF5
* I2O5
* IO2F
* IOF3

Iodine(VII)|

* HIO4
* H5IO6
* IF7
* IO3F
* IO2F3
* IOF5

* v
* t
* e

Salts and covalent derivatives of the iodide ion

| HI
+H |  |  |  | He

|
|
|
|

LiI | BeI2 | BI3
+BO3 | CI4
+C | NI3
NH4I
+N | I2O4
I2O5
I2O6
I4O9 | IF
IF3
IF5
IF7 | Ne
NaI | MgI2 | AlI
AlI3 | SiI4 | PI3
P2I4

PI5 | S2I2 | ICl
ICl3 | Ar
KI | CaI2 |  | ScI3 | TiI2
TiI3
TiI4 | VI2
VI3 | CrI2
CrI3
CrI4 | MnI2 | FeI2
FeI3 | CoI2 | NiI2
-Ni | CuI | ZnI2 | GaI
GaI3 | GeI2
GeI4
+Ge | AsI3
As2I4
+As | Se  | IBr
IBr3 | Kr
RbI
RbI3 | SrI2 |  | YI3 | ZrI2
ZrI3
ZrI4 | NbI4
NbI5 | MoI2
MoI3 | TcI3 | RuI3 | RhI3 | PdI2 | AgI | CdI2 | InI
InI3 | SnI2
SnI4 | SbI3
+Sb | TeI4
+Te | I−

3 | Xe
CsI
CsI3 | BaI2 |  | LuI3 | HfI3
HfI4 | TaI4
TaI5 | WI2
WI3
WI4 | ReI3
ReI
4 | OsI
OsI2
OsI3 | IrI3
IrI
4 | PtI2
PtI4 | AuI
AuI3 | Hg2I2
HgI2 | TlI
TlI3 | PbI2 | BiI3 | PoI2
PoI4 | AtI | Rn
Fr  | RaI2 |  | Lr  | Rf  | Db  | Sg  | Bh  | Hs  | Mt  | Ds  | Rg  | Cn  | Nh  | Fl  | Mc  | Lv  | Ts  | Og
| ↓  |  |
| LaI2
LaI3 | CeI2
CeI3 | PrI2
PrI3 | NdI2
NdI3 | PmI3 | SmI2
SmI3 | EuI2
EuI3 | GdI2
GdI3 | TbI3 | DyI2
DyI
3 | HoI3 | ErI3 | TmI2
TmI3 | YbI2
YbI3
AcI3 | ThI2
ThI3
ThI4 | PaI4
PaI5 | UI3
UI4 | NpI3 | PuI3 | AmI2
AmI3 | CmI3 | BkI
3 | CfI

CfI
3 | EsI2
EsI3 | Fm  | Md  | No

* v
* t
* e

Monatomic anion compounds

Group 1|

* H−

Group 13|

* B
* Al
* Ga
* In
* Tl

Group 14|

* C
* Si
* Ge
* Sn
* Pb

Group 15 (Pnictides)|

* N3−
* P3−
* As3−
* Sb3−
* Bi3−

Group 16 (Chalcogenides)|

* O2−
* S2−
* Se2−
* Te2−
* Po2−

Group 17 (Halides)|

* F−
* Cl−
* Br−
* I−
* At−

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