Potassium-40

Potassium-40 is a naturally occurring radioactive isotope of potassium that decays mainly into calcium-40 and, through electron capture, into argon-40. Its long half-life makes it useful for dating rocks and a source of natural background radiation.

Radioactive decay: The spontaneous transformation of unstable atomic nuclei into other nuclei, accompanied by emitted particles or radiation. Potassium-40 changes into argon-40 or calcium-40 through radioactive decay.
Potassium-argon dating: A radiometric dating method that compares potassium-40 in a sample with radiogenic argon-40. It uses potassium-40’s decay to estimate the ages of potassium-bearing rocks.
Potassium: A reactive chemical element with atomic number 19, found in minerals and essential to living cells. Potassium-40 is one of potassium’s naturally occurring isotopes.
Radiogenic heat: Heat released inside a planet by the radioactive decay of isotopes in its materials. Potassium-40 decay contributes to Earth’s internal heat budget.
Beta decay: A nuclear decay process in which a neutron changes into a proton, or a proton into a neutron, with emission of a beta particle. Potassium-40 produces calcium-40 through beta-minus decay.
Argon-argon dating: A radiometric dating method that estimates age by comparing argon isotopes after neutron irradiation of a sample. It derives ages from potassium-40 decay while allowing multiple measurements on one mineral sample.
Isotope: One of two or more atoms of the same element with different numbers of neutrons. Potassium-40 differs from stable potassium isotopes by its neutron count.
Natural background radiation: Ionizing radiation continually present in the environment from natural and cosmic sources. Potassium-40 is a source of radiation in rocks, food, and living organisms.
Electron capture: A nuclear process in which an atomic nucleus absorbs an inner-shell electron, converting a proton into a neutron. This pathway turns potassium-40 into argon-40.
Radiometric dating: The determination of an object's age from measured radioactive decay and the abundance of parent and daughter isotopes. Potassium-40 is one of the isotopes used to establish geological ages.

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