Question

The number of atoms contained in a fcc unit cell of a monoatomic substance is__________.

• A. $1$
• B. $2$
• C. $4$
• D. $6$

Answer 1

The correct option is C $4$

The number of atoms contained in a fcc unit cell of a monoatomic substance is $4$. Atoms are present at the corners as well as centers of the faces of the cube. Thus, there are $8$ atoms at the corners (each one contributes one eight to the unit cell) and $6$ atoms at face centers (each one contributes one half to the unit cell). Thus, total $14$ atoms are present.

Total contribution is $8\times \frac{1}{8}+6\times \frac{1}{2}=1+3=4$