Chapter 21, Problem 21.1E

Interpretation Introduction

Interpretation:

The reason as to why ionic crystals are brittle on the basis of an atomic-level is to be stated.

Concept introduction:

A substance that is hard but easy to break is known as a brittle substance. Ionic crystal is composed of positively charge ion, cations and negatively charged ion, anions. Crystal lattice is $\text{3D}$ arrangement of the points in a crystal.

Answer to Problem 21.1E

Due to the strong interactions between the ions, the ionic crystal is hard, but once distortion occurs in the crystal, the repulsion of ions take place which results in the destabilization of the crystal. This destabilization causes crystal to break.

Explanation of Solution

Ionic crystals are composed of cations and anions. The negatively and positively charged ions in the native state are placed by each other. The attraction between these ions is strong and due to the strong interactions between the ions, the ionic crystal is hard.

The normal lattice becomes distorted once a crystal is stressed. Due to this distortion, the same charge ions come close together. Hence, they repel each other and causes destabilization of the crystal. Thus, due to destabilization, ionic crystal is easy to break.

Conclusion

Due to the strong interactions between the ions, the ionic crystal is hard, but once distortion occurs in the crystal, the repulsion of ions take place which results in the destabilization of the crystal. This destabilization causes crystal to break.