Copper crystallises into a $fcc$ lattice with edge length $3.61 \times 10^{-8} \, cm$. Show that the calculated density is in agreement with its measured value of $8.92 \, g \, cm^{-3}$.

Edge length,$a = 3.61 \times 10^{-8} \, cm$.
As the lattice is $fcc$ type,the number of atoms per unit cell,$z = 4$.
Atomic mass of copper,$M = 63.5 \, g \, mol^{-1}$.
Avogadro's number,$N_{A} = 6.022 \times 10^{23} \, mol^{-1}$.
Applying the density formula:
$d = \frac{z \times M}{a^{3} \times N_{A}}$
$d = \frac{4 \times 63.5 \, g \, mol^{-1}}{(3.61 \times 10^{-8} \, cm)^{3} \times 6.022 \times 10^{23} \, mol^{-1}}$
$d = \frac{254}{47.045881 \times 10^{-24} \times 6.022 \times 10^{23}} \, g \, cm^{-3}$
$d = \frac{254}{28.33} \, g \, cm^{-3} \approx 8.97 \, g \, cm^{-3}$.
The calculated density $8.97 \, g \, cm^{-3}$ is in close agreement with the measured value of $8.92 \, g \, cm^{-3}$.