Chapter 3, Problem 3H.34E

(a)

Interpretation Introduction

Interpretation:

Structure type of solid ${\text{NH}}_4\text{F}$ has to be determined.

Concept Introduction:

Radius ratio of smaller ion to larger ion in solid-state is used to represent relative size of larger ion. This radius ratio is used to predict structure of unit cell from crystal lattice as follows:

$\begin{array}{ccc}\text{Radius ratio}& \text{Crystal structure}& \text{Coordination number}\\ <0.4& \text{zinc-blende structure}& 4\\ 0.4-0.7& \text{rock-salt structure}& 6\\ >0.7& \text{cesium-chloride structure}& 8\end{array}$

Expression to calculate radius ratio $\left(\rho \right)$ is as follows:

  $\rho =\frac{r_{\text{smaller}}}{r_{\text{larger}}}$        (1)

(b)

Interpretation Introduction

Interpretation:

Structure type of solid ${\text{NH}}_4\text{I}$ has to be determined.

Concept Introduction:

Refer to part (a).