Question

Why do ionic compounds have high melting points?

• A. Ionic compounds have strong electrostatic forces of attraction between the ions. Therefore, it requires a lot of energy to overcome these forces.
• B. Ionic compounds are formed by the transfer of a proton between two atoms. Thus, the formation of the cation and anion takes place.
• C. Ionic compounds have weak electrostatic forces of attraction between the ions. Therefore, it requires a less of energy to overcome these forces.
• D. Ionic compounds are formed by the sharing of electron between two atoms.

Hint:

The high melting point of ionic solids (such as \(NaCl\), melting point \(\approx 801^\circ\text{C}\)) is a direct consequence of their strong, non-directional electrostatic lattice energy.
Breaking this giant lattice requires significant thermal energy.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks for the fundamental reason why ionic compounds possess characteristically high melting and boiling points.

Step 2: Key Formula or Approach:
Analyze the nature of the chemical bonds and the structural lattice arrangement in ionic solids.

Step 3: Detailed Explanation:

• Ionic compounds are formed by the complete transfer of one or more electrons from a metallic atom (forming a positive cation) to a non-metallic atom (forming a negative anion).

• These oppositely charged ions (\(\text{M}^{n+}\) and \(\text{X}^{m-}\)) arrange themselves in a highly ordered, three-dimensional crystalline giant lattice structure.

• Within this lattice, each ion is surrounded by oppositely charged neighbors and is held in place by very strong electrostatic forces of attraction (ionic bonds) described by Coulomb's Law:
\[ F = k \frac{q_1 q_2}{r^2} \]

• Because these electrostatic forces are extremely powerful and act in all directions throughout the entire crystal lattice, a vast amount of thermal energy is required to break these strong bonds and free the ions from their fixed positions.

• Consequently, a very high temperature is needed to melt or boil an ionic solid.

• Let us evaluate the other options:
- Option (B): Incorrect, because ionic compounds are formed by the transfer of electrons, not protons.
- Option (C): Incorrect, because the forces of attraction are strong, not weak.
- Option (D): Incorrect, because electron sharing forms covalent bonds, not ionic bonds.


Step 4: Final Answer:
Ionic compounds have high melting points because they have strong electrostatic forces of attraction between the ions, requiring a lot of energy to overcome them.