Question

Which is the reason that ionic compounds are brittle?

Answer 1

The ionic compounds are very hard and brittle. In ionic compounds the ions are rigidly held in a lattice because the positive and negative ions are strongly attracted to each other and difficult to separate. But the brittleness of a compound is how easy it is to shift the position of atoms or ions in a lattice. If we apply a pressure on the ionic compounds the layers shifts slightly. the Same charged ions in the lattice comes closer. A repulsive forces arises between same charged ions. due to this repulsions the lattice structure breaks down .

Answer 2

The reason why ionic compounds are hard and brittle is because the ions in the compound are already held rigidly in place in a lattice due to the strong electrostatic forces of attraction in between the cations and the anions as well as the repulsion in the ions with like charges . However, if a large enough force is applied along a certain plane, this causes the ions to shift along that layer, displacing that layer with respect to the next, and there will hence be a repulsion between like charges within the ionic compound. This repulsion will shatter the crystal lattice of the ionic compound.