Which of the following are not characteristic properties of ionic solids?

A. The bonding forces are Coulombic or electrostatic attraction.

B. They are hard but brittle.

C. They are malleable and ductile.

D. They are insulators in solid and liquid states.

E. Their melting points are high.

Choose their correct answer from the options given below.

C and D only

The correct answer is option 3. C and D only.

Let us look into the details of each option:

A. The bonding forces are Coulombic or electrostatic attraction.

This statement is correct. Ionic solids are composed of positively and negatively charged ions, and the primary bonding force holding them together is the strong electrostatic attraction between oppositely charged ions.

B. They are hard but brittle.

This statement is generally true. Ionic solids tend to be hard due to the strong ionic bonds between ions. However, they are often brittle because the layers of ions cannot easily slide past one another without disrupting the lattice structure. This brittleness makes them prone to fracture.

C. They are malleable and ductile.

This statement is incorrect. Ionic solids are typically not malleable and ductile. Malleability and ductility are characteristics associated with metallic bonding, where there is a delocalized sea of electrons allowing layers of metal ions to slide past each other without breaking. In contrast, ionic solids lack this electron mobility, leading to brittleness.

D. They are insulators in solid and liquid states.

This statement is incorrect. Ionic solids are electrical insulators in the solid state. However, in the molten state or when dissolved in water, the ions become free to move about and they conduct electricity.

E. Their melting points are high.

This statement is generally true. Ionic solids have high melting points because a significant amount of energy is required to overcome the strong electrostatic forces holding the ions together. As the temperature rises, the ionic lattice structure must be broken, leading to a high melting point.