For which ionic compound is the radius ratio $0.93$?

An example of fluorite structure is

In a face-centered cubic lattice,a unit cell face is shared equally by how many unit cells?

In an ionic crystal,$\frac{r^{+}}{r^{-}} = 0.524$,the coordination number of the cation is:

$Na$ and $Mg$ crystallise in $b.c.c.$ and $f.c.c.$ type crystals respectively. The number of atoms of $Na$ and $Mg$ present in the unit cell of their respective crystals is:

The edge lengths of a simple cubic $(sc)$ and a face-centered cubic $(fcc)$ unit cell are equal. The ratio of the volume occupied by atoms in these two structures is .....