What is the number of octahedral voids present in $0.2 \ mol$ of a compound forming $hcp$ structure?

How will you distinguish between the following pairs of terms:
$(iii)$ Tetrahedral void and octahedral void?

Which of the following lattices has the highest packing efficiency: $(i)$ simple cubic,$(ii)$ body-centred cubic,and $(iii)$ hexagonal close-packed lattice?

$A$ compound of formula $A_2B_3$ has the $hcp$ lattice. Which atom forms the $hcp$ lattice and what fraction of tetrahedral voids is occupied by the other atoms?

In a $ccp$ structure of $X$ atoms,$Y$ atoms occupy half of the octahedral voids. If one $X$ atom and one $Y$ atom in each unit cell are replaced by a $Z$ atom,the molecular formula of the solid will be:

In an ionic solid, anions $(B)$ are arranged in an $hcp$ array and cations $(A)$ occupy $1/2$ of the tetrahedral voids. What is the formula of the ionic compound?