For a tetrahedral structure,the limiting radius ratio $r_c^+ / r_a^-$ is .......

What is the coordination number of $Zn^{2+}$ and $S^{2-}$ ions in the zinc blende $(ZnS)$ structure?

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

The compound $AB$ crystallizes in a cubic lattice in which both $A$ and $B$ atoms have coordination numbers of $8$. To what crystal class does the unit cell belong?

What is the coordination number of $Zn$ in the crystal structure of $Zn$?

In a body-centered cubic $(BCC)$ structure like $CsCl$,the distance between the two nearest neighboring spheres is equal to: