Iodine

Isotopes

There are 37 isotopes of iodine and only one, I-127, is stable. The artificial radioisotope I-131 (a beta emitter), also known as radioiodine which has a half-life of 8.0207 days, has been used in treating cancer and other pathologies of the thyroid glands. The most common compounds of iodine are the iodides of sodium and potassium (KI) and the iodates (KIO3).

Related Topics:
Isotope - Radioisotope - Radioiodine - Half-life - Cancer - Thyroid - Gland - Sodium - Potassium - KI

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I-129 (half-life 15.7 million years) is a product of Xe-129 spallation in the atmosphere and uranium and plutonium fission, both in subsurface rocks and nuclear reactors. Nuclear processes, in particular nuclear fuel reprocessing and atmospheric nuclear weapons tests have now swamped the natural signal for this isotope. I-129 was used in rainwater studies following the Chernobyl accident. It also has been used as a ground-water tracer and as an indicator of nuclear waste dispersion into the natural environment.

Related Topics:
Half-life - Xe - Spallation - Atmosphere - Uranium - Plutonium - Chernobyl accident

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In many ways, I-129 is similar to chlorine-36. It is a soluble halogen, fairly non-reactive, exists mainly as a non-sorbing anion, and is produced by cosmogenic, thermonuclear, and in-situ reactions. In hydrologic studies, I-129 concentrations are usually reported as the ratio of I-129 to total I (which is virtually all I-127). As is the case with Cl-36/Cl, I-129/I ratios in nature are quite small, 10-14 to 10-10 (peak thermonuclear I-129/I during the 1960s and 1970s reached about 10-7). I-129 differs from Cl-36 in that its half-life is longer (15.7 vs. 0.301 million years), it is highly biophilic, and occurs in multiple ionic forms (commonly, I- and iodate) which have different chemical behaviors. This makes it fairly easy for I-129 to enter the biosphere as it becomes incorporated into vegetation, soil, milk, animal tissue, etc.

Related Topics:
Chlorine - Anion - Ion

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Excesses of Xe-129 in meteorites have been shown to result from decay of I-129. This was the first extinct radionuclide to be identified as present in the early solar system. Its decay is the basis of the I-Xe radiometric dating scheme, which covers the first 50 million years of solar system evolution.

Related Topics:
Extinct radionuclide - Solar system - Radiometric dating

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