An example of fluorite structure is

The ratio of the effective number of atoms in a unit cell of $fcc$ and $bcc$ lattices is

The number of nearest neighbours and next nearest neighbours of an $Na^{+}$ ion in a crystal of $NaCl$ are respectively

Calculate the volume occupied by all particles in a $bcc$ unit cell if the volume of the unit cell is $8.0 \times 10^{-23} \ cm^3$.

$(i)$ What is meant by the term 'coordination number'?
$(ii)$ What is the coordination number of atoms:
$(a)$ in a cubic close-packed structure?
$(b)$ in a body-centred cubic structure?

An ionic compound has a unit cell 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 for this compound would be