Chapter 9, Problem 61QRT

Interpretation Introduction

Interpretation:

The no. of unit cells sharing each of the $N{a}^{+}$ ions in the front face of the unit cell has to be determined.  The no. of unit cells sharing each of the $C{l}^{-}$ ions in this face also has to be determined.

Concept Introduction:

Fcc unit cell:

In a fcc unit cell, six atoms lie in the centers of the six faces of the cube contributing $1/2$ to the unit cell.  Eight atoms lie at the eight corners of the cube contributing $1/8$ to the unit cell.  Hence, total no. of atoms per fcc unit cell is $8\times \frac{1}{8}+6\times \frac{1}{2}=4.$