What is the radius ratio $r^+/r^-$ for $NaCl$?

In a face-centred cubic $(FCC)$ lattice,atoms of $A$ form the corner points and atoms of $B$ form the face-centred points. If two atoms of $A$ are missing from the corner points,the formula of the ionic compound is

The coordination number of the sphere in cubic close packed $(ccp)$ structure is

What is the total number of adjacent unit cells shared by each face particle of an $fcc$ unit cell?

$A$ cubic lattice has atoms of $A$ at the body centre,atoms of $B$ at the corners of the cube and atoms $C$ at all the face centres. What is its formula?

$A$ compound is formed by elements $A$ and $B$. This crystallizes in a cubic structure where atoms $A$ are at the corners of the cube and atoms $B$ are at the body center. The simplest formula of the compound is: