Potassium fluoride $(KF)$ has an $NaCl$ type structure. What is the distance between $K^{+}$ and $F^{-}$ ions if the unit cell edge length is $a \ cm$?

In the calcium fluoride structure,the coordination number of the cation and anion are respectively:

$A$ cubic solid is made of two elements $P$ and $Q$. Atoms of $Q$ are at the corners of the cube and $P$ at the body-centre. What is the formula of the compound? What are the coordination numbers of $P$ and $Q$?

For an ionic crystal $A^{+}B^{-}$ with coordination number $6$,the radius ratio will be

Number of atoms per unit cell for body centered cubic system is

What is the coordination number in a hexagonal close-packed $(h.c.p.)$ structure?