$A$ compound is formed from elements $X$ and $Y$. The atoms of $Y$ (anions) form a $ccp$ lattice. The atoms of $X$ (cations) occupy half of the octahedral voids and half of tetrahedral voids. What is the formula of the compound?

In a crystal lattice,anions $A$ form an $hcp$ array,and $2/3$ of the tetrahedral voids are occupied by cations $C$. What is the formula of the crystal?

In which of the following crystals are all the tetrahedral voids occupied?

$A$ metal crystallizes in a simple cubic unit cell. Calculate the void volume of the unit cell. $[a = 3.36 \times 10^{-8} \text{ cm}]$

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

In a compound $AB_2O_4$,the oxide ions form a cubic close-packed $(CCP)$ lattice. The molar ratio of trivalent cations to bivalent cations is $2:1$. If all the bivalent ions occupy octahedral voids and trivalent ions occupy both tetrahedral and octahedral voids in equal numbers,then the fraction of octahedral voids that remain unoccupied is: