The coordination number in $hcp$ is

The edge length of the unit cell of $NaCl$ crystal lattice is $552 \, pm$. If the ionic radius of the sodium ion is $95 \, pm$, what is the ionic radius of the chloride ion in $pm$?

$A$ solid $A^{+}B^{-}$ has a $NaCl$ type close-packed structure. If the radius of the anion is $250 \ pm$, what should be the ideal radius of the cation in $pm$?

The sum of the number of first and second nearest neighbors in an $FCC$ closed packing is:

Structure similar to zinc blende is found in

$A$ compound crystallizes in a $NaCl$ type structure. What is the percentage of unoccupied tetrahedral voids?