Question

Give reasons for the following: Ionic compounds have generally high melting points and boiling points.

Hint:

Strong ionic bonds → High melting and boiling points.

Answer 1

Reason: Ionic Compounds Have Generally High Melting and Boiling Points

Ionic compounds have generally high melting points and boiling points because of the strong electrostatic forces of attraction between oppositely charged ions present in them.

Detailed Explanation:

1. Nature of Ionic Bond:
Ionic compounds are formed by the transfer of electrons from a metal atom to a non-metal atom. As a result, positively charged ions (cations) and negatively charged ions (anions) are formed.

2. Strong Electrostatic Forces:
These oppositely charged ions are held together by very strong electrostatic forces of attraction (ionic bonds). These forces act in all directions within a crystal lattice structure.

3. Large Amount of Energy Required:
To melt or boil an ionic compound, a large amount of heat energy is required to overcome these strong forces of attraction between the ions.

4. Crystal Lattice Structure:
Ionic compounds exist as rigid three-dimensional crystal lattices. Breaking this strong lattice arrangement requires high temperature.

Example:
Sodium chloride (NaCl) has a melting point of about 801°C, which is very high compared to many covalent compounds.

Conclusion:
Therefore, ionic compounds have high melting and boiling points because strong electrostatic forces between oppositely charged ions require a large amount of energy to break.