Question

Explain the following:
i) The basis of similarities and differences between metallic and ionic crystals.
ii) Ionic solids are hard and brittle.

Answer 1

Hint- In order to explain both the points we will start by discussing the force, melting point, electric property of metallic crystals as well as ionic crystals, we will find similarities and differences on the basis of these points.

Complete step-by-step answer:
The basis of similarities and differences between metallic and ionic crystals are given below:
Similarities: Both ionic and metallic crystals have electrostatic attractive forces. In ionic crystals, the forces are present between oppositely charged ions and in metallic crystals; the forces are between valence electrons and kernels. Due to this, both crystals have high melting points. Both crystals have non directional bonds.
Differences: Ionic crystals do not conduct electricity in solid state as ions are not free to move. They conduct electricity in molten states and in aqueous solutions. Molecular crystals conduct electricity in solid state as valence electrons are free to move.
Ionic bonds in ionic crystals are strong due to electrostatic attractive forces. However, in metallic crystals, the metallic bond may be weak or strong depending upon the number of valence electrons and the size of the kernels.

Ionic solids are hard due to the presence of strong electrostatic attractive forces among oppositely charged ions. Due to the non directional nature of ionic bonds, the ionic solids are brittle.

Note- Iron, nickel, selenium, tantalum, tellurium, tin, titanium, niobium, rhenium, tungsten, vanadium, indium, cobalt, chromium, cadmium, manganese, molybdenum, bismuth, arsenic, antimony, aluminium, and zinc are some examples of metallic crystals. Sodium iodide, Sodium chloride, Sodium bromide, Sodium fluoride, Potassium iodide, Potassium bromide, Potassium chloride, Potassium fluoride are some examples of ionic crystals.