# How many copper atoms in a 63.55*g mass of copper metal?

By definition, there are ${N}_{A} , \text{Avogadro's number}$ of copper atoms in a $63.55 \cdot g$ mass of copper wire.
And ${N}_{A} , \text{Avogadro's number}$ $=$ $6.022 \times {10}^{23}$ individual copper atoms.
I look on the Periodic Table, and at $Z = 29$, i.e. copper, the quoted atomic mass is $63.55 \cdot g$. The quoted mass is the mass of $\text{Avogadro's number}$ of copper atoms. And thus, given a reaction with, say, oxygen or sulfur, I can calculate an equivalent, STOICHIOMETRIC mass of sulfur or oxygen.