I-131 is also a major fission product of uranium-233, produced from thorium.Due to its mode of beta decay, iodine-131 is notable for causing mutation and death in cells that it penetrates, and other cells up to several millimeters away.Gamma rays are released during both types of radioactive decay.When an isotope emits an alpha particle, the resultant daughter product has an atomic number two units less than its parent's atomic number, and an atomic weight four units less than its parent's atomic weight.
All the others disintegrate spontaneously with the release of energy by processes broadly designated as radioactive decay.
Once an organism is dead, however, no new carbon is actively absorbed by its tissues, and its carbon 14 gradually decays.
Libby thus reasoned that by measuring carbon 14 levels in the remains of an organism that died long ago, one could estimate the time of its death.
Most carbon consists of the isotopes carbon 12 and carbon 13, which are very stable.
A very small percentage of carbon, however, consists of the isotope carbon 14, or radiocarbon, which is unstable.