In a compound,atoms of element $Y$ form $ccp$ lattice and those of element $X$ occupy $2/3$ of tetrahedral voids. The formula of the compound will be

The correct option for the number of tetrahedral and octahedral voids in a hexagonal primitive unit cell is:

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:

The volume of the $HCP$ unit cell is

In the closest packing of atoms,

Atoms of an element $Z$ form a hexagonal closed packed $(hcp)$ lattice and atoms of element $X$ occupy all the tetrahedral voids. The formula of the compound is