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Rutherford applied the principle of a radioactive element's half-life in studies of age determination of rocks by measuring the decay period of radium to lead-206. Half-life is constant over the lifetime of an exponentially decaying quantity, and it is a characteristic unit for the exponential decay equation. The accompanying table shows the ...
Radioactive isotope table "lists ALL radioactive nuclei with a half-life greater than 1000 years", incorporated in the list above. The NUBASE2020 evaluation of nuclear physics properties F.G. Kondev et al. 2021 Chinese Phys. C 45 030001. The PDF of this article lists the half-lives of all known radioactives nuclides.
Specific activity (symbol a) is the activity per unit mass of a radionuclide and is a physical property of that radionuclide. [1] [2] It is usually given in units of becquerel per kilogram (Bq/kg), but another commonly used unit of specific activity is the curie per gram (Ci/g).
In principle a half-life, a third-life, or even a (1/√2)-life, could be used in exactly the same way as half-life; but the mean life and half-life t 1/2 have been adopted as standard times associated with exponential decay. Those parameters can be related to the following time-dependent parameters:
The biological half-lives "alpha half-life" and "beta half-life" of a substance measure how quickly a substance is distributed and eliminated. Physical optics: The intensity of electromagnetic radiation such as light or X-rays or gamma rays in an absorbent medium, follows an exponential decrease with distance into the absorbing medium.
Hg with a half-life of 444 years, and 203 Hg with a half-life of 46.612 days. Most of the remaining radioisotopes have half-lives that are less than a day. 206 Hg occurs naturally in tiny traces as an intermediate decay product of 238 U. 199 Hg and 201 Hg are the most often studied NMR-active nuclei, having spins of 1 ⁄ 2 and 3 ⁄ 2 ...
[16] 233 Th (half-life 22 minutes) occurs naturally as the result of neutron activation of natural 232 Th. [30] 226 Th (half-life 31 minutes) has not yet been observed in nature, but would be produced by the still-unobserved double beta decay of natural 226 Ra. [31] In deep seawaters the isotope 230 Th makes up to 0.02% of natural thorium. [8]
The radioactivity is of academic interest because bismuth is one of a few elements whose radioactivity was suspected and theoretically predicted before being detected in the laboratory. [9] Bismuth has the longest known α-decay half-life, though tellurium-128 has a double beta decay half-life of over 2.2 × 10 24 years. [43]