What are the stable isotopes of carbon?

12C and 13C are the most stable isotopes in carbon because they do not deteriorate into another form or element over time.

(The 12 and 13 are supposed to be small like an exponent, my keyboard lacks that function)

By far the most common isotope of carbon is carbon-12 (12C), which contains six neutrons in addition to its six protons. The next heaviest carbon isotope, carbon-13 (13C), has seven neutrons. Both 12C and 13C are called stable isotopes since they do not decay into other forms or elements over time.