# Does the mass of an isotope directly relate to the molar mass of the atom?

No, we need a multiplier, and the multiplier is Avogadro's number, ${N}_{A}$.
We often cite atomic mass as $12.00 \cdot g ,$ ""^12C, $16.00 \cdot g$, ""^16O, of course, here we refer to the mass of a mole, $\text{Avogadro's number}$, of such isotopes. Now, the actual mass of a single isotope, a single atom, is (of course) considerably less than these gram quantities. Nevertheless, chemists deal (typically) in gram quantities, and using $\text{Avogadro's number}$ we can relate the macro world of grams and kilograms to the micro world of atoms and molecules.