Question

Aluminium metal has face centred cubic (f.c.c.) structure. The number of $'Al'$ atoms per unit cell of the lattice is

• A. 2
• B. 1
• C. 4
• D. 6

Answer 1

Answer: (C)

4

Answer 2

In a unit cell there are $8$ corners and $6$ faces. Since each comer of the unit cell is shared by eight unit cells, and each face is shared by two unit cells, the number of points per face unit cell $Z = 8 \times \frac{1}{8} +6 \times + \frac{1}{2}$ $= 1 + 3 = 4$