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?

In a close-packed lattice,the number of tetrahedral voids compared to the number of octahedral voids is:

What is the percentage of unoccupied space in $fcc$ unit cell (in $\%$)?

In a crystalline solid with the formula $AB_2O_4$,the oxide ions are arranged in a cubic close-packed $(CCP)$ lattice,while the cations $A$ are present in tetrahedral voids and cations $B$ are present in octahedral voids. What are the percentages of tetrahedral and octahedral voids occupied by $A$ and $B$ respectively?

The fraction of voids occupied in the inverse spinel compounds are

If the number of tetrahedral voids in a crystal lattice is $N$,then the number of close-packed spheres will be ..........