Types of Solid

Crystalline solids

The solids of definite shape with its atoms or molecules arranged in some regular repetitious three dimensional patterns are termed as crystalline solids. For example; Rock salt, calcite, sugar, quartz, Copper Sulphate (CuSO₄) etc. 

A periodic and regular arrangement of points in space is known as a lattice arrangement. In a crystalline structure, the various atoms or molecules are attached to the lattice in an identical manner. The distances between the various particles constituting a crystal are of the order of the size of these particles. The mean potential energy of every particle is more than its kinetic energy and their vibrationals about the position of equilibrium are extremely limited. The crystalline solids have generally sharp melting points and are anisotropic in nature i.e., the values of conductivity, elasticity, tensile strength, refractive index vary with direction. In summary crystalline solids have following characteristics.

1. They have regular and periodic arrangement of atoms or ions or molecules.

2. They have long range spatial order in their structure. 

3.They have not the same physical properties.

4. Their compositions may be homogenous.

5. They have sharp melting point.

6. They are anisotropic in nature.

7. Examples are diamond, graphite, sodium chloride etc.

Amorphous solids

Amorphous solids are those solids in which the atoms are not arranged in regular geometrical patterns. In the amorphous solids, the molecules do not form a regular spatial lattice and are in a more or less chaotic and random distribution throughout the solid, even though the distance between nearest molecules is of the same order as that of the molecules in crystalline such substances without any regular form of shape.

Amorphous solids do not have sharp melting point and are isotropic in nature i.e., the value of conductivity, elasticity, tensile strength, etc. remain same and do not vary with direction. In summary amorphous solids have following characteristics.

1. They have not regular and periodic arrangement of atoms or ions or molecules.

2. They have short range spatial order in their structure.

3. They have the same physical properties. 

4. Their compositions may not be homogenous.

5. They have not sharp melting point.

6. They are isotropic in nature.

7. Examples are ordinary glass, Sulphur, Plastics etc.