| Iodine - I
CAS:7553-56-2 Description: Shiny, grayish-black flakes or violet gas Classification: Halogen Date of Discovery: 1811 Discoverer: Bernard Courtois Name Origin: Greek iôdes, "violet" |
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Atomic Number: 53
Number of Neutrons: 74 Atomic Mass: 126.90447(3) amu Melting Point: 113.7 °C Boiling Point: 184.4 °C Density (293 K): 4.93 g/cm3 11.27 g/l (gas) Atomic volume: 25.74 cm3/mol Electrical resistivity: 8.0e-16 10-6/cm 
Thermal conductivity: 0.00449 W/cmK Enthalpy of atomization: 106.7 kJ/mol Enthalpy of vaporization: 20.752 kJ/mol Enthalpy of fusion: 7.824 kJ/mol Specific heat capacity: 0.214 J/gK |
Energy levels: 2-8-18-18-7
Electron configuration: [Kr]4d105s25p5 Crystal Structure: Orthorhombic Atomic radius: 1.32 Å Covalent radius: 1.33 Å Oxidation States: -1, +1, +3, +5, +7 Electronegativity, Pauling: 2.66 Electron affinity: 3.059038 eV First ionization energy: 10.451 eV 2nd ionization energy: 19.131 eV 3rd ionization energy: 33.0 eV Polarizability: 4.7 10-24cm3 |
| Isotope | Natural Abundance | Atomic Mass | Half-life | Decay Mode | Spin |
| 108I | 107.9436 | 0.04 s |  - |
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| 109I | 108.9382 | 0.11 ms | p | ||
| 110I | 109.9346 | 0.65 s |  +, EC; ; p |
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| 111I | 110.9303 | 2.5 s | +, EC |
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| 112I | 111.9280 | 3.4 s | +, EC |
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| 113I | 112.9237 | 5.9 s | +, EC |
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| 114I | 113.9219 | 2.1 s | +, EC |
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| 115I | 114.9188 | 1.3 m | +, EC |
5/2+ | |
| 116I | 115.9167 | 2.9 s | +; EC |
1+ | |
| 117I | 116.9136 | 2.22 m | +, EC |
(5/2+) | |
| 118mI | 8.5 m | +, EC; IT |
7- | ||
| 118I | 117.9134 | 14 m | +, EC |
2- | |
| 119I | 118.9102 | 19 m | +; EC |
(5/2+) | |
| 120mI | 53 m | +; EC |
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| 120I | 119.91005 | 1.35 h | +; EC |
2- | |
| 121I | 120.90737 | 2.12 h | +; EC |
5/2+ | |
| 122I | 121.90760 | 3.6 m | +; EC |
1+ | |
| 123I | 122.905605 | 13.2 h | EC | (5/2+) | |
| 124I | 123.906211 | 4.18 d | +; EC |
2- | |
| 125I | 124.90464 | 59.4 d | EC | 5/2+ | |
| 126I | 125.905619 | 13.0 d | EC; +; - |
2- | |
| 127I | 100. | 126.904468 | Stable | 5/2+ | |
| 128I | 127.905805 | 25.00 m | -; EC |
1+ | |
| 129I | 128.904988 | 1.7 x 107 y | - |
7/2+ | |
| 130mI | 9.0 m | IT; - |
2+ | ||
| 130I | 129.906674 | 12.36 h | - |
5+ | |
| 131I | 130.906125 | 8.040 d | - |
7/2+ | |
| 132mI | 1.39 h | IT | 8- | ||
| 132I | 131.90800 | 2.28 h | -; IT |
4+ | |
| 133mI | 9 s | IT | 19/2- | ||
| 133I | 132.90781 | 20.8 h | - |
7/2+ | |
| 134mI | 3.7 m | IT; - |
8- | ||
| 134I | 133.9099 | 52.6 m | - |
4+ | |
| 135I | 134.91005 | 6.57 h | - |
7/2+ | |
| 136mI | 47 s | - |
6- | ||
| 136I | 135.91466 | 1.39 m | - |
2- | |
| 137I | 136.91787 | 24.5 s | - |
(7/2+) | |
| 138I | 137.9224 | 6.5 s | - |
2- | |
| 139I | 138.92609 | 2.30 s | -; n |
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| 140I | 139.9310 | 0.86 s | -; n |
(3) | |
| 141I | 140.9351 | 0.45 s | - |
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| 142I |  0.2 s |
- |
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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, in Chilean saltpeter
and nitrate-bearing earth, known as caliche in brines from old sea deposits, and in brackish waters from oil and salt wells. Ultrapure iodine can be obtained from the reaction of potassium iodide with copper sulfate. Several other methods of isolating the element are known. Iodine is a bluish-black, lustrous solid, volatilizing at ordinary temperatures into a blue-violet gas with an irritating odor; it forms compounds with many elements, but is less active than the other halogens, which displace it from iodides. Iodine exhibits some metallic-like properties. It dissolves readily in chloroform, carbon tetrachloride, or carbon disulfide to form beautiful purple solutions. It is only slightly soluble in water. Iodine compounds are important in organic chemistry and very useful in medicine. Forty-two isotopes and isomers 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. Iodides, and thyroxin which contains iodine, are used internally in medicine, and 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. Care should be taken in handling and using iodine as contact with the skin can cause lesions; iodine vapor is intensely irritating to the eyes and mucous membranes.
LINKS: Bacteria in Drinking Water, Bulletin 795 - Iodine Cancer of the Thyroid Iodine Saturation Spectroscopy International Council for the Control of Iodine Deficiency Disorders Iodine - HealthWorld Online LCSS: IODINE Thyroid Home Page Return
Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998. |
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