What is the coordination number of $Cs^{+}$ and $Cl^{-}$ ions in the $CsCl$ structure?

The coordination number of the point $B$ for a solid with the following structure is:

What is the coordination number of a particle in $hcp$ structure?

$A$ solid compound contains atoms $X, Y,$ and $Z$. In its unit cell,atoms $X$ are at the corners,atoms $Y$ are at the body center,and atoms $Z$ are at the face centers. The formula of the compound is:

If the cation is present in the tetrahedral void,what is the radius ratio ${r_ + }/{r_ - }$?

The number of atoms in body-centred and face-centred cubic unit cells are, respectively: