There are 3 isotopes of carbon. Carbon-12, Carbon-13 and Carbon-14. The average atomic mass of carbon is 12.011. Which isotope of carbon is the most abundant? Why?
The most abundant carbon isotope is carbon-12.
The relative atomic mass of carbon is 12.011, which is extremely close to 12.0. This means that the masses C-13, and C-14 are practically negligible when contributing to the relative atomic mass of carbon.
In fact, the C-12 isotope makes up 98.9% of carbon atoms, C-13 makes up 1.1% of carbon atoms, and C-14 makes up just a trace of carbon atoms as they are found in nature.