Chapter 3, Problem 3H.29E

(a)

Interpretation Introduction

Interpretation:

Coordination number of solid $\text{RbF}$ 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)

Here,

$r_{\text{smaller}}$ is radius of smaller ion.

$r_{\text{larger}}$ is radius of larger ion.

(b)

Interpretation Introduction

Interpretation:

Coordination number of solid $\text{MgO}$ has to be determined.

Concept Introduction:

Refer to part (a).

(c)

Interpretation Introduction

Interpretation:

Coordination number of solid $\text{NaBr}$ has to be determined.

Concept Introduction:

Refer to part (a).