The arrangement $ABC ABC ABC …..$ is referred to as:

In chrysoberyl,a compound containing beryllium,aluminium and oxygen,oxide ions form a cubic close-packed structure. Aluminium ions occupy $\frac{1}{4}$ of the octahedral voids and beryllium ions occupy $\frac{1}{8}$ of the tetrahedral voids. The formula of the compound is

The compound forming $ccp$ structure contains $9.6 \times 10^{23}$ atoms. Find the number of tetrahedral voids formed in it.

$A$ compound is formed by two elements $X$ and $Y$. The element $Y$ forms a cubic close-packed $(CCP)$ arrangement and the atoms of element $X$ occupy one-third of the tetrahedral voids. What is the formula of the compound?

How will you distinguish between the following pairs of terms:
$(i)$ Hexagonal close-packing $(hcp)$ and cubic close-packing $(ccp)$?

The number of octahedral and tetrahedral holes respectively present in a hexagonal close packed $(hcp)$ crystal of $X$ atoms are