How many copper atoms are there in a solid cube of copper which is 1.00 cm on each side? What is the approximatesize of atom ? The atomic mass of copper is 63.6 g/mol and the density is 8.96 g/cm³.

The volume of the copper cube is 1 cm³. So the mass is 8.96 g. = $\frac{8.96}{63.6}=0.14$ mole of copper.
Now 1 mole copper is equal to $6.023\times {10}^{23}$ number of atoms. Therefore number of atoms in the cube is $6.023\times {10}^{23}\times 0.14=8.43\times {10}^{22}$.

Now the approximate size of an atom is $\frac{volume }{\text{number of atoms}}=\frac{1}{8.43\times {10}^{22}}=1.18$ cm³