Types of Solids on The Basis of Biding Forces

Types of Solids on The Basis of Biding Forces:- The crystalline solids may be classified into four types depending upon the nature of bonds present in them.

(i)          Molecular crystals are generally soft.

(ii)         They have low melting points

(iii)        These are bad conductors of electricity and are regarded as electrical insulators.

(iv)       They are volatile and have low heats of vaporization.

The common examples of molecular crystals are: - Solid carbon dioxide, ice, iodine.

Ionic crystals:- the ionic crystals consist of positively and negatively charged ions arranged in a regular fashion throughout the crystal. Thus, in ionic crystals, the constituent particles are ions. These are held together by strong electrostatic forces. The main characteristics of ionic crystals are:-

(i)          Ionic crystals are very hard and brittle.

(ii)         They have very high melting and boiling points.

(iii)        They are poor conductors of electricity and therefore, are insulators in the solid state.

(iv)       They have high heats of vaporization.

Covalent crystals:- In covalent crystals, the constituent particles are atoms which are linked to one another by covalent bonds. The important characteristics of covalent crystals are:-

(i)          They covalent crystals are hard.

(ii)         They have very high melting points.

(iii)        They are poor conductors of electricity.

(iv)       They have high heated fusion.

Metallic Crystals: - in metallic crystals the constituent particles are positive ions immersed in a sea of mobile electrons. The forces present between the constituents are metallic bonds. The metallic bonds spread over the entire crystal. The bonding is non directional. The main characteristics of metallic crystals are:-

(i)          Metallic crystals may be hard as well as soft.

(ii)         They are good conductors of heat and electricity.

(iii)        They have metallic luster.

(iv)       They are malleable and ductile. Due to malleable nature, they can be beaten into sheets and because of their ductile nature they can be drawn into wires.

(v)         They have moderate heat of fusion.