Aluminium crystallizes in an fcc structure. The atomic radius of the metal is 125 pm. What is the length of the side of the unit cell of the metal?

• For a face-centred cubic lattice structure of crystal

r = where, r = radius of the sphere (components of the crystal- like an atom) s= edge length of the unit cell.

• Hence , a =r X 2√2 = 2 X 125 X 1.414 (√2 = 1.414 )

=353.5 pm.