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Carbon (6 C) has 14 known isotopes, from 8 C to 20 C as well as 22 C, of which 12 C and 13 C are stable.The longest-lived radioisotope is 14 C, with a half-life of 5.70(3) × 10 3 years. . This is also the only carbon radioisotope found in nature, as trace quantities are formed cosmogenically by the reactio
Archaeological materials, such as bone, organic residues, hair, or sea shells, can serve as substrates for isotopic analysis. Carbon, nitrogen and zinc isotope ratios are used to investigate the diets of past people; these isotopic systems can be used with others, such as strontium or oxygen, to answer questions about population movements and cultural interactions, such as trade.
The standard used for modern carbon is wood, with a baseline date of 1950. [5] Correcting for fractionation changes the activity measured in the sample to the activity it would have if it were wood of the same age as the sample. The calculation requires the definition of a 13 C fractionation factor, which is defined for any sample material as [6]
Sulfur isotope ratios are almost always expressed as ratios relative to 32 S due to this major relative abundance (95.0%). Sulfur isotope fractionations are usually measured in terms of δ 34 S due to its higher abundance (4.25%) compared to the other stable isotopes of sulfur, though δ 33 S is also sometimes measured.
D 0 is number of atoms of the daughter isotope in the original or initial composition, N(t) is number of atoms of the parent isotope in the sample at time t (the present), given by N(t) = N 0 e −λt, and; λ is the decay constant of the parent isotope, equal to the inverse of the radioactive half-life of the parent isotope [19] times the ...
Carbon on Earth naturally occurs in two stable isotopes, with 98.9% in the form of 12 C and 1.1% in 13 C. [1] [8] The ratio between these isotopes varies in biological organisms due to metabolic processes that selectively use one carbon isotope over the other, or "fractionate" carbon through kinetic or thermodynamic effects. [1]
The most widely studied and used isotopes in archaeology are carbon, oxygen, nitrogen, strontium and calcium. [2] An isotope is an atom of an element with an abnormal number of neutrons, changing their atomic mass. [2] Isotopes can be subdivided into stable and unstable or radioactive. Unstable isotopes decay at a predictable rate over time. [2]
The number of nucleons (both protons and neutrons) in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number. For example, carbon-12, carbon-13, and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13, and 14, respectively. The atomic number of carbon is 6, which means that ...