Stableisotope
Stable isotopes are non-radioactive isotopes of chemical elements whose nuclei are stable on geological timescales. Most elements have at least one stable isotope, and some have several. Common examples include carbon-12 and carbon-13, nitrogen-14 and nitrogen-15, and the oxygen isotopes oxygen-16, oxygen-17, and oxygen-18, as well as hydrogen-1 (protium) and deuterium (hydrogen-2). The natural abundances of these isotopes vary by element and source, giving each element a characteristic isotopic composition.
In measurements and notation, isotopic ratios are typically expressed using delta values (δ) relative to international standards.
Applications of stable isotopes span many disciplines. In earth and environmental sciences, stable isotopes are used
Notes: stable isotopes can be fractionated—enriched or depleted—in natural and experimental processes, producing characteristic isotopic signatures.