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 Points and Boiling Points

Ionic compounds have high melting and boiling points because the particles in these compounds are held together by very strong electrostatic forces of attraction.

Detailed Explanation:

1. Formation of Ions:
Ionic compounds are formed by the complete transfer of electrons from a metal to a non-metal. This transfer creates positively charged ions (cations) and negatively charged ions (anions).

2. Strong Electrostatic Attraction:
The oppositely charged ions attract each other very strongly. These attractive forces are called ionic bonds. Since these forces are very strong, they hold the ions firmly in a rigid crystal lattice structure.

3. Large Amount of Heat Required:
To melt or boil an ionic compound, these strong ionic bonds must be broken. Breaking such strong electrostatic forces requires a large amount of heat energy. Therefore, ionic compounds melt and boil only at high temperatures.

4. Crystal Lattice Structure:
In solid state, ionic compounds exist as three-dimensional crystal lattices in which each ion is surrounded by several oppositely charged ions. This arrangement increases the strength of attraction and stability of the compound.

Example:
Sodium chloride (NaCl) melts at about 801°C, which shows that a high temperature is needed to overcome the strong ionic bonds.

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