Answer
Please see the work below.
Work Step by Step
We can find the number of copper atoms in a modern penny as follows
$0.63g\space Cu\times (\frac{1 mol \space Cu }{63.55g\space Cu})(6.022\times 10^{23}Cu \frac{atoms}{1mol\space Cu})=6.0\times 10^{20}Cu\space atoms$
