. Explain similarities and differences between metallic and ionic crystals
(i) The basis of similarities and differences between metallic and ionic crystals.
(ii) Ionic solids are hard and brittle.
Hint : Consider the force of attraction, its strength, movement of ions etc., to give answer.
(a) Ionic and metallic crystals both have electrostatic force of attraction. In ionic crystals, this force is between oppositely charged ions whereas in metals, this force is in between the Valence electrons and the kernels.
(b) In both cases, bond is non-directional.
(a) In ionic crystals, ions are not free to move. So, they don't conduct electricity in solid state. They are conductors only in molten .state or aqueous solution. In metals, valence electrons can move. Hence, they can conduct electricity in solid state.
(b) Ionic bonds are strong whereas metallic bonds may be weak or strong
(ii) Ionic crystals are hard because there are strong electrostatics forces of attraction among the oppositely charged ions. They are brittle because ionic bond is non-directional