Copper crystallizes in $f.c.c.$ with a unit cell length of $361 \ pm$. What is the radius of copper atom? (in $pm$)

In a mineral $MX_2$,$M^{+2}$ ions are arranged in a $ccp$ structure and $X^{-}$ ions occupy the tetrahedral voids. What are the number of cations and anions per unit cell,the coordination number of the cation,and the percentage of occupied tetrahedral voids,respectively?

In an ionic crystal,ion $A$ is present at the corners of the cubic unit cell,and ion $B$ is present at the centers of the faces. What is the formula of this ionic compound?

What is the limiting radius ratio for a tetrahedral shape?

The structure of $MgO$ is similar to that of $NaCl$. What is the coordination number of $Mg^{2+}$?

The number of equidistant oppositely charged ions in a sodium chloride crystal is