Isotopes of carbon
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Carbon (6C) has 14 known isotopes, from 8
C to 20
C as well as 22
C, of which only 12
C and 13
C are stable. The longest-lived radioisotope is 14
C, with a half-life of 5700 years. This is also the only carbon radioisotope found in nature, as trace quantities are formed cosmogenically by the reaction 14
N + n → 14
C + 1
H. The most stable artificial radioisotope is 11
C, which has a half-life of 20.34 minutes. All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds. Lighter isotopes exhibit beta-plus decay into isotopes of boron and heavier ones beta-minus decay into isotopes of nitrogen, though at the limits particle emission occurs as well. The two lightest isotopes decay into helium via short-lived isotopes of lithium, beryllium and boron.