Chemistry - Solid State Question with Solution | TestHub

Total volume of the metal is given by the ratio of mass to density.

$V_{\text{total}}=\frac{\text{Mass}}{\text{Density}}=\frac{18}{7.2}=2.5{\text{cm}}^3$

The number of unit cells is the total volume divided by the volume of one unit cell.

$\text{Number of unit cells}=\frac{V_{\text{total}}}{V_{\text{unit cell}}}=\frac{2.5}{2.5\times 10^{-23}}=1.0\times 10^{23}$

Answer: $1.0\times 10^{23}$