Question

How many atoms constitute one unit cell of a face-centered cubic crystal?

Answer 1

In face centred cubic unit cell (fcc) each particle is at the corner and at face centres.

Corner atoms contribute $\frac{1}{8}$ per unit cell and face centre atoms contribute $\frac{1}{2}$.

Now,

No. of atoms $=8\times \frac{1}{8}+6\times \frac{1}{2}=4$