Overview

Carbon-14 is a naturally occurring radioactive variant of carbon, identified as an isotope of the element carbon. Its nucleus contains six protons and eight neutrons, giving it an atomic mass of 14 and a specific arrangement of particles in the atomic nucleus. Because of its instability it slowly decays, and this property underlies the technique widely known as radiocarbon dating.

Formation and decay

Carbon-14 forms in the upper atmosphere when cosmic rays strike atmospheric gases and produce neutrons; those neutrons convert stable nitrogen-14 into carbon-14 by nuclear reaction. As a beta emitter, carbon-14 decays back to nitrogen-14 while emitting an electron and an antineutrino. The process is characterized by a half-life of about 5,730 years, meaning half of a given amount decays in that interval.

Principle of radiocarbon dating

Living plants and animals continuously exchange carbon with their environment, keeping a roughly constant ratio of carbon-14 to stable carbon isotopes. When an organism dies this exchange stops and the carbon-14 fraction decreases by radioactive decay. Measuring the remaining carbon-14 relative to stable carbon allows estimation of the time since death. Laboratories typically report ages in years "before present" (BP) and apply calibration curves derived from tree rings and other records to convert measured ratios into calendar years.

Uses and practical considerations

Radiocarbon dating is a cornerstone method in archaeology, palaeontology, geology, and forensic science for dating organic remains such as wood, bone, charcoal, peat, and shell. Practical limits arise from the isotope's half-life and measurement sensitivity: conventional techniques are effective up to roughly 50,000–60,000 years, beyond which remaining carbon-14 is extremely low. Key challenges include contamination by modern carbon, reservoir effects (for example in marine samples), and the need for careful sample preparation and calibration.

Characteristics, advantages and notable facts

  • Characteristic: radioactive beta decay to nitrogen-14 with a known half-life, enabling time estimates.
  • Advantage: direct dating of once-living material without reliance on associated artifacts.
  • Limitations: decreasing accuracy at great age, contamination, and local reservoir offsets that require correction.
  • Notable: calibration with dendrochronology, varved sediments, and other independent records improves calendar-age accuracy.

For introductory resources on isotopes and atomic structure see the linked terms above. For specialized methods such as accelerator mass spectrometry (AMS) or sample pretreatment protocols, consult technical literature and laboratory guides that explain advances in detection sensitivity and contamination control.