potassium-40
Sign in to savePotassium-40 (K) is a long lived and the main naturally occurring radioactive isotope of potassium, with a half-life of 1.248 billion years. It makes up about 117 of natural potassium, making that mixture very weakly radioactive; the short life means this was significantly larger earlier in Earth's history.
Key facts
- Isotope.symbol
- K
- Isotope.mass_number
- 40
- Isotope.mass
- 39.963998
- Isotope.num_neutrons
- 21
- Isotope.num_protons
- 19
- Isotope.image
- Potassium-40.svg
- Isotope.decay_product
- Calcium-40
- Isotope.decay_symbol
- Ca (β−)
- Isotope.decay_mass
- 40
- Isotope.decay_product2
- Argon-40
- Isotope.decay_symbol2
- Ar (EC, γ; β+)
- Isotope.decay_mass2
- 40
- Isotope.decay_mode1
- β−
- Isotope.decay_energy1
- 1.3109
- Isotope.decay_mode2
- EC
- Isotope.decay_energy2
- 1.5044
- Isotope.decay_mode3
- β+
- Isotope.parent
- Primordial nuclide
via Wikipedia infobox
Article
7 sectionsContents
- Potassium–argon dating
- Contribution to natural radioactivity
- Banana equivalent dose
- See also
- Notes
- References
- External links
Potassium-40 (K) is a long lived and the main naturally occurring radioactive isotope of potassium, with a half-life of 1.248 billion years. It makes up about 117 of natural potassium, making that mixture very weakly radioactive; the short life means this was significantly larger earlier in Earth's history.
Potassium-40 undergoes four different paths of radioactive decay, including all three main types of beta decay: Electron emission (β) to Ca with a decay energy of 1.31 MeV at 89.6% probability Electron capture (EC) to Ar followed by a gamma decay emitting a photon with an energy of 1.46 MeV at 10.3% probability Direct electron capture (EC) to the ground state of Ar at 0.1% probability Positron emission (β) to Ar at 0.001% probability