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Potassium-40 (40 K) is a radioactive isotope of potassium which has a long half-life of 1.25 billion years. It makes up about 0.012% (120 ppm ) of the total amount of potassium found in nature. Potassium-40 undergoes three types of radioactive decay .
All other potassium isotopes have half-lives under a day, most under a minute. The least stable is 31 K, a three-proton emitter discovered in 2019; its half-life was measured to be shorter than 10 picoseconds. [5] [6] Stable potassium isotopes have been used for several nutrient cycling studies since potassium is a macronutrient required for ...
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.
Potassium-40 has a half-life of 1.3 billion years, so this method is applicable to the oldest rocks. Radioactive potassium-40 is common in micas , feldspars , and hornblendes , though the closure temperature is fairly low in these materials, about 350 °C (mica) to 500 °C (hornblende).
t 1/2 is the half-life of 40 K; K f is the amount of 40 K remaining in the sample; Ar f is the amount of 40 Ar found in the sample. The scale factor 0.109 corrects for the unmeasured fraction of 40 K which decayed into 40 Ca; the sum of the measured 40 K and the scaled amount of 40 Ar gives the amount of 40 K which was present at the beginning ...
A further 10 nuclides, platinum-190, samarium-147, lanthanum-138, rubidium-87, rhenium-187, lutetium-176, thorium-232, uranium-238, potassium-40, and uranium-235 have half-lives between 7.0 × 10 8 and 4.83 × 10 11 years, which means they have experienced at least 0.5% depletion since the formation of the Solar System about 4.6 × 10 9 years ...
half-life (t 1/2) mode product; 39 K 93.3% stable: 40 K: 0.0120% ... Traces of 40 K are found in all potassium, and it is the most common radioisotope in the human ...
In principle a half-life, a third-life, or even a ... For example, in a sample of potassium-40, 89.3% of the nuclei decay to calcium-40 and 10.7% to argon-40.