# The unit cell of metallic gold is face centred cubic.What is the mass of a gold unit cell?

$\begin{array}{1 1}8.177\times 10^{-23}g\\4.177\times 10^{-23}g\\6.177\times 10^{-23}g\\7.177\times 10^{-23}g\end{array}$

Mass of gold atom=$\large\frac{\text{Molar mass}}{\text{Avagadro's number}}$
$\Rightarrow \large\frac{197}{6.023\times 10^{23}}\times \frac{1}{4}$g
$\Rightarrow 8.177\times 10^{-23}$g