Give two examples of metals that crystallize in the $hcp$ (hexagonal close-packed) structure.

If the anion $(A)$ forms a hexagonal closest packing and the cation $(C)$ occupies only $2/3$ of the octahedral voids in it,then the general formula of the compound is :-

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

In an ionic solid,anions $(B)$ are arranged in an $hcp$ array and cations $(A)$ occupy $\frac{2}{3}$ of the octahedral voids. What is the formula of the ionic compound?

Which one of the following statements about packing in solids is incorrect?

Calculate the void volume in an $fcc$ unit cell if the total volume of the unit cell is $6.4 \times 10^{-23} \text{ cm}^3$.