Question

The number of atoms per unit cell in gold is_________.

• A. $3$
• B. $4$
• C. $2$
• D. $1$

Answer 1

The correct option is B $4$

Gold has an fcc unit cell. It contains $8$ atoms at the $8$ corners. Each atom at a corner is shared by $8$ unit cells. In addition, it contains $6$ atoms at $6$ faces. Each atom at a face is shared by $2$ unit cells.
Thus, the total number of gold atoms present in the unit cell is $\frac{1}{8}\times 8+\frac{1}{2}\times 6=4$ atoms.