What is the limiting radius ratio for a tetrahedral shape?

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

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

If three elements $A, B, C$ crystallize in a cubic solid lattice with $B$ atoms at the cubic centers, $C$ atoms at the center of edges, and $A$ atoms at the corners, then the formula of the compound is

An element occurring in the $bcc$ structure has $12.08 \times 10^{23}$ unit cells. The total number of atoms of the element in these cells will be:

The empirical formula for a compound with a cubic close packed arrangement of anions and with cations occupying all the octahedral sites is $A_{x}B$. The value of $x$ is ..... .
(Integer answer)