In a $BCC$ lattice containing $X$ and $Y$ type of atoms, $X$ type of atoms are present at the corners and $Y$ type of atoms are present at the body center. In its unit cell, if three atoms are missing from the corners, the formula of the compound is:

Explain the crystal structure of sodium chloride $(NaCl)$.

What is the coordination number of a cation present in a tetrahedral void?

An example of fluorite structure is

Explain how much portion of an atom located at $(i)$ corner and $(ii)$ body centre of a cubic unit cell is part of its neighbouring unit cell.

An element crystallizes in a structure such that the unit cell is a cube with one atom at each corner and two atoms on its body diagonal. If the volume of this unit cell is $24 \times 10^{-24} \, cm^3$ and the density of the element is $7.2 \, g \, cm^{-3}$,calculate the number of atoms present in $200 \, g$ of the element.