Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 with a nucleus
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...

 containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating
Radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...

 method pioneered by Willard Libby
Willard Libby
Willard Frank Libby was an American physical chemist noted for his role in the 1949 development of radiocarbon dating, a process which revolutionized archaeology....

 and colleagues (1949), to date archaeological, geological, and hydrogeological samples.

Carbon-14 was discovered on 27 February 1940, by Martin Kamen
Martin Kamen
Martin David Kamen , a physicist inside the Manhattan project. Together with Sam Ruben, he co-discovered the isotope carbon-14 on February 27, 1940, at the University of California Radiation Laboratory, Berkeley....

 and Sam Ruben
Sam Ruben
Samuel Ruben , the son of Herschel and Frieda Penn Rubenstein – the name was officially shortened to Ruben in 1930...

 at the University of California Radiation Laboratory in Berkeley
Berkeley, California
Berkeley is a city on the east shore of the San Francisco Bay in Northern California, United States. Its neighbors to the south are the cities of Oakland and Emeryville. To the north is the city of Albany and the unincorporated community of Kensington...

, although its existence had been suggested by Franz Kurie
Franz N. D. Kurie
Franz Newell Devereux Kurie was an American physicist who, while working at Yale in 1933, showed that the neutron was neither a dumb-bell-shaped combination of proton and electron, nor an onion-shaped combination of an electron embracing the proton...

 in 1934.

There are three naturally occurring isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...

s of carbon on Earth: 99% of the carbon is carbon-12
Carbon-12 is the more abundant of the two stable isotopes of the element carbon, accounting for 98.89% of carbon; it contains 6 protons, 6 neutrons, and 6 electrons....

, 1% is carbon-13
Carbon-13 is a natural, stable isotope of carbon and one of the environmental isotopes. It makes up about 1.1% of all natural carbon on Earth.- Detection by mass spectrometry :...

, and carbon-14 occurs in trace amounts, i.e.
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