Final answer:
Ionic solids have very high melting points due to the energy needed to break strong ionic bonds, and they are brittle because shifting ion layers cause repulsion when like-charged ions come into contact.
Step-by-step explanation:
Ionicsolids have very high melting points and the solids are very brittle. These properties are due to the ordered crystal lattice and the strong electrostatic forces of attraction between the oppositely charged ions in the lattice. High melting points are the result of the energy required to break the strong ionic bonds that hold the crystal lattice together.
Despite their hardness, which measures resistance to deformation, ionic solids are brittle because when a mechanical force causes a shift in the layers of ions, like-charged ions are brought next to each other which leads to repulsion and causes the material to shatter.