The coordination number of a cation occupying a tetrahedral hole is

In a crystal of $LiI$, $I^{-}$ ions are arranged in a $ccp$ structure and $Li^{+}$ ions occupy octahedral voids. If $a = 600 \ pm$, what is the radius of the $Li^{+}$ ion in $pm$?

The face diagonal length of $f.c.c.$ cubic cell is $660 \sqrt{2} \, pm$. If the radius of the cation is $110 \, pm$,the radius of the anion is ............ $pm$.

What is the number of atoms per unit cell in a body-centered cubic $(BCC)$ unit cell?

The coordination number of a sphere in a face-centered cubic $(fcc)$ lattice is .....

What is the coordination number of the $hcp$ crystal lattice?