Carbon-13 (${}^{13}\mathrm{C}$)

Carbon-13 (C-13) is a stable isotope of carbon, which has an atomic mass of approximately 13 atomic mass units (amu). It consists of six protons and seven neutrons in its nucleus, distinguishing it from the more common carbon isotope, Carbon-12 (C-12), which has six protons and six neutrons. Carbon-13 makes up about 1.1% of all naturally occurring carbon in the environment.