Chapter 9, Problem 118QRT

Interpretation Introduction

Interpretation:

The interionic distance of Barium sulfide has to be calculated and a comparison of this value with the sum of ionic radii has to be done.

Concept Introduction:

$NaCl$ has fcc type structure.

Fcc unit cell:

Eight atoms occupy the corner position of a cube each contributing $1/8$ to the unit cell and six atoms occupy the center of each face of the unit cell contributing $1/2$ to the unit cell.  Hence, the total number of atoms present in one unit cell is $8\times \frac{1}{8}+6\times \frac{1}{2}=4$.

Density:

It is the ration of mass and volume of a substance.  Mathematically, it can be represented as given below.

  $d=\frac{m}{v}$

Where, $d$  is density, $m$  is mass of a substance and $v$ is volume of a substance

Volume of a cubic unit cell:

Volume of cubic unit cell $=a^3$