What is the coordination number of $Ag^+$ in a $AgCl$ crystal lattice?

The number of unit cells present in $39 \ g$ of potassium if it crystallizes as a body-centered cubic $(BCC)$ structure is ($N = \text{Avogadro number}$, $\text{At. wt. of potassium} = 39$).

In a face-centred cubic $(FCC)$ lattice,atoms of $A$ form the corner points and atoms of $B$ form the face-centred points. If two atoms of $A$ are missing from the corner points,the formula of the ionic compound 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 structure of $MgO$ is similar to that of $NaCl$. What is the coordination number of $Mg^{2+}$?

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 ........... $pm$.