Why are ionic compounds brittle in nature?

Ionic compounds are brittle because when stress is applied, their orderly arrangement of ions is disrupted, causing them to break.

Ionic compounds are made up of positive and negative ions arranged in a regular, repeating pattern known as a crystal lattice. This structure is very stable due to the strong electrostatic forces of attraction between the oppositely charged ions. However, this same structure also makes ionic compounds brittle.

When an external force or stress is applied to an ionic compound, it can cause the layers of ions to shift. This shift can bring ions of the same charge into close proximity with each other. As like charges repel, this causes a repulsive force between these ions. This repulsion can cause the crystal lattice to break apart, resulting in the brittle nature of ionic compounds.

For example, consider sodium chloride (NaCl), a common ionic compound. In its crystal lattice, each sodium ion (Na+) is surrounded by chloride ions (Cl-) and vice versa. When a force is applied, it can cause a shift in the layers of ions. This can bring Na+ ions next to each other or Cl- ions next to each other. As these ions repel each other, it can cause the crystal to fracture or break, demonstrating the brittleness of ionic compounds.

In summary, the brittleness of ionic compounds is a direct result of their crystal lattice structure. While this structure provides stability and high melting and boiling points due to the strong electrostatic forces of attraction, it also leads to brittleness when the layers of ions are disrupted by an external force. This is a key characteristic of ionic compounds that distinguishes them from other types of compounds, such as covalent compounds, which tend to be more flexible due to the nature of their bonding.