Explain- (i) The basis of similarities and differences between metallic and ionic crystal (ii) Ionic solids are hard and brittle.

Explanation

(i) Similarities: In both ionic and metallic crystals, binding forces are electrostatic in nature and non-directional.

(ii) Ionic crystals are hard due to strong electrostatic forces of attraction among constituent oppositely charged ions.
When a shearing force is applied on an ionic crystal, some of the layers of ions slide a bit over the other layer and ions of similar charges suddenly come closer to each other. At this moment, the ions of similar charges strongly repel each other and this repulsion causes the breaking of the crystal. Thus, ionic arystals are brittle in nature.