Gold (atomic radius = 0.144 nm) crystallises in a face-centred unit cell. What is the length of a side of the cell?
Given, atomic radius = 0.144 nm
Type of unit cell = face centered
We know that side (a) in fcc 
Thus, a = 
0.144 nm
a = 2 × 1.414 × 0.144 = 407 nm.
Thus the side of the given cell = 407 nm.
24