# What is the total number of atoms in a cubic based unit cell having one atom on each corner and two atoms on each diagonal?

$\begin{array}{1 1} 8 \\ 12 \\ 9 \\ 11 \end{array}$

Answer: $9$ atoms.
Number of atoms contributed by 8 corner atoms $= \large\frac{1}{8}$$\times 8 = 1$
Number of atoms contributed by 4 diagonals $= 4 \times 2 = 8$
$\Rightarrow$ the total number of atoms $= 1 + 8 = 9$.