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# 6.11B: Structure - Caesium Chloride (CsCl)


This page is going to discuss the structure of the molecule cesium chloride ($$\ce{CsCl}$$), which is a white hydroscopic solid with a mass of 168.36 g/mol. Cesium Chloride is a type of unit cell that is commonly mistaken as Body-Centered Cubic. This misconception is easy to make, since there is a center atom in the unit cell, but CsCl is really a non-closed packed structure type.

## Introduction

CsCl has a boiling point of 1303 degrees Celsius, a melting point of 646 degrees Celsius, and is very soluble in water. For the most part this molecule is stable, but is not compatible with strong oxidizing agents and strong acids. Although it is not hazardous, one should not prolong their exposure to CsCl. CsCl is an ionic compound that can be prepared by the reaction:

$\ce{Cs2CO3 + 2HCl -> 2 CsCl + H2O + CO2}$

CsCl crystallize in a primitive cubic lattice which means the cubic unit cell has nodes only at its corners. The structure of CsCl can be seen as two interpenetrating cubes, one of Cs+ and one of Cl-. The ions are not touching one another. Touching would cause repulsion between the anion and cation. Some may mistake the structure type of CsCl with NaCl, but really the two are different. CsCl is more stable than NaCl, for it produces a more stable crystal and more energy is released.

Anions and cations have similar sizes. Each Cs+ is surrounded by 8 Cl- at the corners of its cube and each Cl- is also surrounded by 8 Cs+ at the corners of its cube. The cations are located at the center of the anions cube and the anions are located at the center of the cations cube. There is one atom in CsCl. To determine this, the following equation is given:

8 Corners of a given atom x 1/8 of the given atom's unit cell = 1 atom

## Applications

Cesium chloride is used in centrifugation, a process that uses the centrifugal force to separate mixtures based on their molecular density. It is also used in the preparation of electrically conducting glasses. Radioactive CsCl is used in some types of radiation therapy for cancer patients, although it is blamed for some deaths.

## References

1. Carter, C. Barry., and M. Grant. Norton. "Binary Compounds." Ceramic Materials Science and Engineering. New York, NY: Springer, 2007. pg87-88
2. Quéré, Yves. "Stable Structure of Halides." Physics of Materials. Amsterdam: Gordon and Breach Science, 1998.

## Contributors and Attributions

• Ana Popovich

6.11B: Structure - Caesium Chloride (CsCl) is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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