What is the percentage of empty space in a $bcc$ unit cell (in $\%$)?

In a $ccp$ arrangement,the percentage of space occupied by spheres is ........ (in $\%$).

Calculate the void volume of a simple cubic unit cell if the volume of the unit cell is $5.5 \times 10^{-22} \ cm^3$.

In a solid $AB_2$,the coordination number of $A$ is $8$. It has a cubic close-packed $(ccp)$ lattice. Half of the $B$ atoms are,however,ejected from the solid. Now,the number of tetrahedral holes (voids) that remain filled is:

$A$ compound is formed by two elements $M$ and $N$. The element $N$ forms $ccp$ lattice and atoms of $M$ occupy $1/3$ of the tetrahedral voids. What is the formula of the compound?

Explain close packing in one dimension. Explain close packing in two dimensions.