Remember isotopes? not all atoms are the same?!
Carbon exists as:
C-12, C-13, and C-14
They
occur in different types, but altogether they can give us an average mass
The average atomic mass for carbon on this planet is 12.01 amu (all the rest are listed on the Periodic Table)
Lets
act, for the rest of chemistry, as if atoms have this one mass, the one listed on the Periodic Table
