How many formula units are there in the unit cell of sodium chloride $(NaCl)$?

$A$ unit cell of calcium fluoride has four calcium ions. The number of fluoride ions in the unit cell is

The number of close neighbours in a body-centred cubic $(BCC)$ lattice of identical spheres is:

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

An ionic compound has unit cells consisting of $A$ ions at the corners of a cube and $B$ ions on the centres of the faces of the cube. The empirical formula of this compound is

What is the volume occupied by particles in $BCC$ structure if '$a$' is the edge length of the unit cell?