Chapter 13.3, Problem 22LC

Interpretation Introduction

Interpretation:

Melting points of ionic and molecular solids are to be compared.

Concept Introduction :

Ions with opposite charges attract one another electrostatically to form compounds known as ionic solids. Van der Waals forces hold the molecules in a molecular solid together.

Answer to Problem 22LC

Ionic solids have high melting points whereas molecular solids have a relatively low melting points.

Explanation of Solution

In an ionic solid like NaCl, ions ( ${\text{Na}}^{+}{\text{ and Cl}}^{-}$ ) are confined very tightly in the crystal structure by a very strong attractive force between the oppositely charged ions. Because it takes a lot of energy to break this connection, ionic solids have high melting points. In molecular solids, weak van der Waals forces exist which require less energy to overcome interactions when converting from solid to liquid.

Thus, ionic solids have high melting points whereas molecular solids have a relatively low melting points.