Chapter 13, Problem 44E

Interpretation Introduction

Interpretation:

Seven lattice and possible variations

Crystal system	Possible variations	Axial distances or edge lengths	Axial angles	Examples
Cubic	Primitive body centred face centred	$a=b=c$	$\alpha =\beta =\gamma ={90}^0$	NaCl,Zinc blende, Cu
Tetragonal	Primitive Body-centred Face-centred	$a=b\ne c$	$\alpha =\beta =\gamma ={90}^0$	White tin${\text{SnO}}_2$ $\text{Ca}S{O}_4$
Orthorhombic	Primitive Body-centred Face-centred	$a\ne b\ne c$	$\alpha =\beta =\gamma ={90}^0$	Rhombic sulfur ${\text{KNO}}_3$ $BaS{o}_4$
Hexagonal	primitive	$a=b\ne c$	$\begin{array}{l}\alpha =\beta ={90}^{\circ }\hfill \\ \gamma ={120}^{\circ }\hfill \end{array}$	Graphite, $ZnO$ $$
Rhombohedral.or Trigonal	primitive	$a=b=c$	$\begin{array}{l}\alpha =\beta ={90}^{\circ }\\ \beta \ne {90}^{\circ }\end{array}$	Calcite$\left(CaC{O}_3\right)$ $HgS\left(cinnabar\right)$
Monoclinic	Primitive	$a\ne b\ne c$	$\begin{array}{l}\alpha =\beta ={90}^{\circ }\\ \beta \ne {90}^{\circ }\end{array}$	Monoclinic sulfur $NaS{O}_4.10H_{2}O$
Triclinic	primitive	$a\ne b\ne c$	$\alpha \ne \beta \ne \gamma \ne {90}^{\circ }$	${\text{K}}_{2}C{r}_2{O}_7$ $CuS{o}_4,5H_{2}O$ $H_{3}B{O}_3$

Concept introduction:

${\text{MX}}_2$: cation: anion coordination number$=8:4\text{ or 6:3}$. It this all tetrahedral half octahedral; alternate layers have fully occupied sites.

It means that coordination number ratio of cation and anion is always$2:1$.

To determine: one of these compounds crystallizes in the fluorite structure: ${\text{Rb}}_{2}O,CaS,Ba{F}_2$.