Carbon-12 is the more abundant carbon of the two stable isotopes, amounting to 98.93% of the element carbon; its abundance is due to the triple-alpha process by which it is created in stars. Carbon-12 is of particular importance in its use as the standard from which atomic masses of all nuclides are measured: its mass number is 12 by definition and contains 6 protons, 6 neutrons and 6 electrons.