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

In a face centered cubic lattice,atoms $A$ are at the corner points and atoms $B$ are at the face centered points. If one atom $B$ is missing from one of the face centered points,the formula of the ionic compound is:

What does the unit cell of $CsCl$ contain?

For $bcc$ cubic coordination the value of radius ratio is

What is the coordination number of sodium in $Na_2O$?

In antifluorite structure,the nearest neighbour distance is $20\sqrt{3} \ pm$. Then,the edge length of the unit cell is ............... $pm$.