Carbon-14

Carbon-14 is a radioactive isotope of carbon with six protons and eight neutrons. Its radioactive decay enables radiocarbon dating, and cosmic rays continually produce it in the atmosphere.

Beta decay: A radioactive decay process in which a neutron becomes a proton or a proton becomes a neutron, emitting a beta particle. Carbon-14 decays by emitting an electron as one neutron becomes a proton.
Radiocarbon dating: A method for estimating the age of once-living material by measuring its remaining carbon-14. This is the isotope’s best-known application.
Isotope: One of two or more atoms of the same element with different numbers of neutrons. Carbon-14 is one isotope within the family of carbon atoms.
Carbon-12: The stable carbon isotope with six protons and six neutrons, making up most naturally occurring carbon. It is the stable reference isotope used to express carbon-14 abundance.
Carbon-14 half-life: The time required for half of a sample’s carbon-14 atoms to decay, about 5,730 years. The half-life sets the timescale used to estimate a sample’s age.
Accelerator mass spectrometry: A technique that separates and counts rare isotopes by accelerating ions and measuring their mass and charge. It can measure carbon-14 directly, including in very small samples.
Radioactive decay: The spontaneous transformation of an unstable atomic nucleus into a more stable state. Carbon-14 disappears through this general nuclear process.
Carbon-13: The stable carbon isotope with six protons and seven neutrons. Its stable abundance helps correct radiocarbon measurements for isotopic fractionation.
Cosmic-ray spallation: The breakup of atomic nuclei when struck by energetic cosmic rays or their secondary particles. Secondary neutrons from cosmic-ray interactions help create carbon-14 in the atmosphere.
Wiggle matching: A dating method that aligns a sequence of radiocarbon measurements with matching variations in a calibration curve. It can date tree-ring sequences more precisely than a single carbon-14 measurement.

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