Back Kalium-40 Afrikaans Potassi 40 Catalan Draslík-40 Czech Potasio 40 Spanish پتاسیم-۴۰ Persian Kalium-40 Finnish Potassium 40 French カリウム40 Japanese 칼륨-40 Korean Калиум-40 Macedonian
| General | |
|---|---|
| Symbol | 40K |
| Names | potassium-40, 40K, K-40 |
| Protons (Z) | 19 |
| Neutrons (N) | 21 |
| Nuclide data | |
| Natural abundance | 0.0117(1)% |
| Half-life (t1/2) | 1.251(3)×109 y |
| Isotope mass | 39.96399848(21) Da |
| Spin | 4− |
| Excess energy | −33505 keV |
| Binding energy | 341523 keV |
| Parent isotopes | Primordial |
| Decay products | 40Ca (β−) 40Ar (EC, γ; β+) |
| Decay modes | |
| Decay mode | Decay energy (MeV) |
| β− | 1.31109 |
| EC, γ | 1.5049 |
| Isotopes of potassium Complete table of nuclides | |
Potassium-40 (40K) 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. In about 89.28% of events, it decays to calcium-40 (40Ca) with emission of a beta particle (β−, an electron) with a maximum energy of 1.31 MeV and an antineutrino. In about 10.72% of events, it decays to argon-40 (40Ar) by electron capture (EC), with the emission of a neutrino and then a 1.460 MeV gamma ray.[Note 1] The radioactive decay of this particular isotope explains the large abundance of argon (nearly 1%) in the Earth's atmosphere, as well as prevalence of 40Ar over other isotopes. Very rarely (0.001% of events), it decays to 40Ar by emitting a positron (β+) and a neutrino.[1]
Cite error: There are <ref group=Note> tags on this page, but the references will not show without a {{reflist|group=Note}} template (see the help page).
- ^ Engelkemeir, D. W.; Flynn, K. F.; Glendenin, L. E. (1962). "Positron Emission in the Decay of K40". Physical Review. 126 (5): 1818. Bibcode:1962PhRv..126.1818E. doi:10.1103/PhysRev.126.1818.
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