Question
How many atoms constitute one unit cell of a face-centered cubic crystal?
Solution
Number of atoms in one face centred cubic unit cell can be determined:-
(i) 8 corners atoms × 1/8 per corner atom = 
= 1 atom
(ii) 6 face-centered atoms × 1/ 2 atom per unit cell = 
= 3 atoms
∴ Total number of atoms per unit cell = 4 atoms
