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 ¹²
C
and ¹³
C
are stable. The longest-lived radioisotope is ¹⁴
C
, with a half-life of 5.70(3)×10³ 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 20.3402(53) min. All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds. The least stable isotope is ⁸
C
, with a half-life of 3.5(1.4)×10⁻²¹ s. Light isotopes tend to decay into isotopes of boron and heavy ones tend to decay into isotopes of nitrogen.