Crystal structure of NaCl

In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure describes a highly ordered structure, occurring due to the intrinsic nature of molecules to form symmetric patterns. A crystal structure can be thought of as an infinitely repeating array of $3$ D 'boxes', known as unit-cells. The above shows the crystal structure of sodium chloride (table salt). How many particles are there in an unit cell of sodium chloride?