* Carbon-12 is the most abundant isotope of carbon, making up about 98.9% of all carbon atoms.

* It has six protons and six neutrons in its nucleus.

* Carbon-12 is the basis for the atomic mass unit (amu), which is defined as exactly 1/12 of the mass of a carbon-12 atom.

* Carbon-12 is stable and does not undergo radioactive decay.

Carbon-14

* Carbon-14 is a radioactive isotope of carbon that has six protons and eight neutrons in its nucleus.

* It is formed in the Earth's atmosphere by the interaction of cosmic rays with nitrogen atoms.

* Carbon-14 has a half-life of 5,730 years, which means that it takes 5,730 years for half of the carbon-14 atoms in a sample to decay.

* Carbon-14 is used in carbon dating, a technique that is used to determine the age of organic materials.

Other Carbon Isotopes

In addition to carbon-12 and carbon-14, there are two other stable isotopes of carbon: carbon-13 and carbon-15. Carbon-13 makes up about 1.1% of all carbon atoms, while carbon-15 makes up only 0.000000000000000000000001% of all carbon atoms.