Iodine
|
Iodine
53I
Br
?
I
?
At
tellurium ? iodine ? xenon
Iodine in the periodic table
Appearance
lustrous metallic gray, violet as a gas
General properties
Name, symbol, number
iodine, I, 53
Pronunciation
/'a?.?da?n/ EYE-?-dyn,
/'a?.?d?n/ EYE-?-d?n,
or /'a?.?di?n/ EYE-?-deen
Element category
diatomic nonmetal
Group, period, block
17 (halogens), 5, p
Standard atomic weight
126.90447
Electron configuration
4d10 5s2 5p5
2, 8, 18, 18, 7
History
Discovery
Bernard Courtois (1811)
First isolation
Bernard Courtois (1811)
Physical properties
Phase
solid
Density (near r.t.)
4.933 g·cm-3
Melting point
386.85 K, 113.7 °C, 236.66 °F
Boiling point
457.4 K, 184.3 °C, 363.7 °F
Triple point
386.65 K, 12.1 kPa
Critical point
819 K, 11.7 MPa
Heat of fusion
(I2) 15.52 kJ·mol-1
Heat of vaporization
(I2) 41.57 kJ·mol-1
Molar heat capacity
(I2) 54.44 J·mol-1·K-1
Vapor pressure (rhombic)
P (Pa)
1
10
100
1 k
10 k
100 k
at T (K)
260
282
309
342
381
457
Atomic properties
Oxidation states
7, 5, 3, 1, -1
(strongly acidic oxide)
Electronegativity
2.66 (Pauling scale)
Ionization energies
1st: 1008.4 kJ·mol-1
2nd: 1845.9 kJ·mol-1
3rd: 3180 kJ·mol-1
Atomic radius
140 pm
Covalent radius
139±3 pm
Van der Waals radius
198 pm
Miscellanea
Crystal structure
orthorhombic
Magnetic ordering
diamagnetic
Electrical resistivity
(0 °C) 1.3×107O·m
Thermal conductivity
0.449 W·m-1·K-1
Bulk modulus
7.7 GPa
CAS registry number
7553-56-2
Most stable isotopes
Main article: Isotopes of iodine
iso
NA
half-life
DM
DE (MeV)
DP
123I
syn
13 h
e, ?
0.16
123Te
124I
syn
4.176 d
e
-
124Te
125I
syn
59.40 d
e
-
125Te
127I
100%
-
(SF)
129I
trace
1.57×107 y
ß-
0.194
129Xe
131I
syn
8.02070 d
ß-, ?
0.971
131Xe
135I
syn
6.57 h
ß-
-
135Xe
Decay modes in parentheses are predicted, but have not yet been observed
v
t
e
· ref
Iodine is a chemical element with symbol I and atomic number 53. The name is from Greek ??e?d?? ioeides, meaning violet or purple, due to the color of elemental iodine vapor.Iodine and its compounds are primarily used in nutrition, and industrially in the production of acetic acid and certain polymers. Iodine's relatively high atomic number, low toxicity, and ease of attachment to organic compounds have made it a part of many X-ray contrast materials in modern medicine. Iodine has only one stable isotope. A number of iodine radioisotopes are also used in medical applications.Iodine is found on Earth mainly as the highly water-soluble iodide ion, I-, which concentrates it in oceans and brine pools. Like the other halogens, free iodine occurs mainly as a diatomic molecule I2, and then only momentarily after being oxidized from iodide by an oxidant like free oxygen. In the universe and on Earth, iodine's high atomic number makes it a relatively rare element. However, its presence in ocean water has given it a role in biology. It is the heaviest essential element utilized widely by life in biological functions (only tungsten, employed in enzymes by a few species of bacteria, is heavier). Iodine's rarity in many soils, due to initial low abundance as a crust-element, and also leaching of soluble iodide by rainwater, has led to many deficiency problems in land animals and inland human populations. Iodine deficiency affects about two billion people and is the leading preventable cause of intellectual disabilities.Iodine is required by higher animals, which use it to synthesize thyroid hormones, which contain the element. Because of this function, radioisotopes of iodine are concentrated in the thyroid gland along with nonradioactive iodine. If inhaled, the radioisotope iodine-131, which has a high fission product yield, concentrates in the thyroid, but is easily remedied with non-radioactive potassium iodide treatment.
Cite error: There are tags on this page, but the references will not show without a {{reflist}} template (see the help page).
|
|
Created By:
System
|
|
|
|
|