Total volume of atoms present in a face-centred cubic unit cell of a metal is ($r$ is atomic radius)

In the fluorite structure,the coordination number of the $Ca^{2+}$ ion is.....

The number of spheres contained $(i)$ in one body centred cubic unit cell and $(ii)$ in one face centred cubic unit cell,is

$A$ binary compound $(A^{+} B^{-})$ has a zinc blende structure where $B^{-}$ ions form the lattice and $A^{+}$ ions occupy $25\%$ of the tetrahedral voids. What is the formula of the compound?

In a face-centered cubic lattice of $X$ and $Y$ atoms,$X$ atoms are present at the corners while $Y$ atoms are at the face centers. If two atoms of $X$ are missing from the corners,what is the formula of the compound?

If the radius ratio for an ionic solid is $0.5248$ and the radius of the cation is $0.95 \ \mathring{A}$,what is the radius of the anion?