Chapter 14, Problem 37A

Interpretation Introduction

Interpretation:

The fact that ionic solids are generally considerably harder than most molecular solids have to be explained.

Concept Introduction:

Crystalline solids are solid compounds with highly ordered structure of the constituents (atoms, molecules or ions). Depending on the constituents (atoms, molecules or ions), the crystalline solids are classified in three types-

1. Ionic solids
2. Molecular solids
3. Atomic solids

Explanation of Solution

The difference in hardness between ionic solids and molecular solids can be explained by considering intermolecular attractive forces which held the constituents together inside the solids. Intermolecular attractive force in ionic solids is the electrostatic attraction between two oppositely charged ions. Due to this attraction, the ions are held together very tightly. Whereas the molecules in a molecular solid are held together by van der Waals forces which is much weaker than the electrostatic force. Due to highly closed packed structure, ionic solids are harder than the molecular solid.