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

In a crystal of $NaCl$, the distance between $Na^{+}$ and $Cl^{-}$ is $x \, pm$. What is the edge length of the unit cell?

$A$ crystal is made up of metal ions $M_1$ and $M_2$ and oxide ions. Oxide ions form a $ccp$ lattice structure. The cation $M_1$ occupies $50 \%$ of octahedral voids and the cation $M_2$ occupies $12.5 \%$ of tetrahedral voids of the oxide lattice. The oxidation numbers of $M_1$ and $M_2$ are,respectively:

The coordination number of a cation occupying a tetrahedral hole is

$A$ metal $X$ crystallises in a face-centred cubic arrangement with the edge length $862 \, pm$. What is the shortest separation of any two nuclei of the atom? ........... $\, pm$

The solid $AB$ has a $NaCl$ type structure. If the radius of the $A^{+}$ ion is $120 \, pm$, then the maximum radius of the $B^{-}$ ion will be ........... $pm$.