$A$ compound is formed by elements $A$ and $B$. Element $A$ occupies the corners of the cube,and element $B$ occupies the face centers. What is the formula of the compound?

An element crystallizes in a structure such that the unit cell is a cube with one atom at each corner and two atoms on its body diagonal. If the volume of this unit cell is $24 \times 10^{-24} \, cm^3$ and the density of the element is $7.2 \, g \, cm^{-3}$,calculate the number of atoms present in $200 \, g$ of the element.

$A$ compound crystallizes in a $NaCl$ type structure. What is the percentage of unoccupied tetrahedral voids?

The structure of $MgO$ is similar to that of $NaCl$. What is the coordination number of $Mg^{2+}$?

$A$ solid $AB$ has a $ZnS$ type structure. If the radius of the $B^-$ ion is $100 \, pm$, what is the minimum radius of the $A^+$ cation in $pm$?

In $NaCl$ the centres of two nearest like charged ions are present at a distance of