# What is the mass of one mole of carbon-12 atoms?

$1$ $m o l$ of ""^12C atoms has a mass of $12.00 \cdot g$ precisely.
The mole is the link between the micro world of atoms and molecules to the macro world of grams and kilograms. By definition, ${N}_{A}$ ""^12C atoms, i.e. $\text{Avogadro's number, } 6.022 \times {10}^{23}$ ""^12C atoms has a mass of $12.00 \cdot g$.
But wait a minute! When I look at the Periodic Table, it gives the equivalent mass of $C$ as $12.011 \cdot g \cdot m o {l}^{-} 1$. Why is there a discrepancy?