Iodine

Images

Image

Attribution: LHcheM

Animated Iodine

History

From the Greek word iodes, violet. Discovered by Courtois in 1811, Iodine, a halogen, occurs sparingly in the form of iodides in sea water from which it is assimilated by seaweeds, Chilean saltpeter, nitrate-bearing earth (known as caliche), brines from old sea deposits, and in brackish waters from oil and salt wells.

Sources

Ultrapure iodine can be obtained from the reaction of potassium iodide with copper sulfate. Several other methods of isolating the element are known.

Uses

Iodine compounds are important in organic chemistry and very useful in medicine. Iodides, and thyroxine which contains iodine, are used internally in medicine, and as a solution of KI and iodine in alcohol is used for external wounds. Potassium iodide finds use in photography. The deep blue color with starch solution is characteristic of the free element.

Isotopes

Thirty isotopes are recognized. Only one stable isotope, 127I is found in nature. The artificial radioisotope 131I, with a half-life of 8 days, has been used in treating the thyroid gland. The most common compounds are the iodides of sodium and potassium (KI) and the iodates (KIO3). Lack of iodine is the cause of goiter.

General Info

AtomicNumber
53
Symbol
I
Name
Iodine

Atomic Info

Appearance
AtomicWeight
126.90447(3)
Color
940094
ElectronicConfiguration
[Kr] 4d10 5s2 5p5
ElectronegativityInPauling
2.66
AtomicRadiusInPM
133
IonRadiusInPM
220 (-1)
VanDerWaalsRadiusInPM
198
IEinKJmol
1008
EAinKJmol
-295
OxidationStates
-1, 1, 3, 5, 7
StandardState
solid
BondingType
covalent network
MeltingPoint
387
BoilingPoint
457
Density
4.94
State
Diatomic nonmetal
DiscoveredYear
1811