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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 .
K (6.7%), and a very long-lived radioisotope 40 K (0.012%) Naturally occurring radioactive 40 K decays with a half-life of 1.248×10 9 years. 89% of those decays are to stable 40 Ca by beta decay, whilst 11% are to 40 Ar by either electron capture or positron emission. This latter decay branch has produced an isotopic abundance of argon on ...
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).
The major natural source of radioactivity in plant tissue is potassium: 0.0117% of the naturally occurring potassium is the unstable isotope potassium-40. This isotope decays with a half-life of about 1.25 billion years (4×10 16 seconds), and therefore the radioactivity of natural potassium is about 31 becquerel/gram (Bq/g), meaning that, in ...
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 ...
Potassium-40 is a radioactive isotope of potassium that decays into argon-40. The half-life of potassium-40 is 1.3 billion years, far longer than that of carbon-14, allowing much older samples to be dated. Potassium is common in rocks and minerals, allowing many samples of geochronological or archeological interest to be dated.
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 ...