Question

Ionic solids are hard and brittle.Explain.

Answer 1

Hint: Ionic solids are basically the solids that are held together by strong ionic bonds, the lattices of which are composed of oppositely charged ions i.e. they consist of positively charged cations and negatively charged anions. These solids tend to have high melting points and are almost electrically insulating.

Complete step by step answer:
Ionic solids are generally hard and brittle, due to the presence of strong electrostatic forces of attraction of the ions in the highly ordered organized crystal lattice structure. The brittleness in these solids are due to the non directional nature of the bonds that bind them i.e. when distorted the like charged ions move closer to each other and shatter the crystal by virtue of their strong electrostatic repulsions.
An example of an ionic solid is table salt, NaCl. Molecular solids—Made up of atoms or molecules held together by London dispersion forces, dipole-dipole forces, or hydrogen bonds. Characterized by low melting points and flexibility and are poor conductors.

Note: One must take note of and remember that the brittleness of the solids could only be tested when immense mechanical pressure is applied on them, when the ions would then get closer to each other for high electrostatic repulsions to occur and split or disorient the lattice infrastructure.