The atomic mass of carbon is approximately 12.011 atomic mass units (u). This value represents the weighted average of the masses of the naturally occurring isotopes of carbon, primarily carbon-12 and carbon-13
. Carbon-12, the most abundant isotope, has an exact atomic mass of 12 u by definition, as it is used as the standard for atomic mass measurements
. The average atomic mass of 12.011 u accounts for the small presence of carbon-13 and other isotopes. Thus, the atomic mass of carbon listed on the periodic table is 12.011 u.
