Classification of solids based on different …

Classification of Crystalline Solids based on Different Binding Forces. Crystalline solids can be classified into different categories depending upon the type of constituent particles and the nature of attractive forces operating between them.

Atomic Solids
In these solids the constituent particles are atoms. These closely packed atoms are held up by London dispersion forces. Some examples are crystals of noble gases. Such solids are very soft, possess very low melting points and poor conductors of heat and electricity.
 

Molecular Solids
In these solids, the constituent particles which pack up together are molecules of the substance. These molecules may be non – polar (dipole moment = 0) such as etc. or they may be polar (dipole moment > 0) like etc.  

In case of non – polar molecules, the attractive forces operating between the molecules are Vander Waal forces (also called dispersion forces). The example of such solids are : dry ice (Solid, iodine (crystals).  

In case of polar molecules, the attractive forces operating between the molecules in solid state are dipole – dipole forces. The examples of such solids are : solid, solid HCl. However, in some solids with polar molecules, the interparticle forces are hydrogen bonds. The examples of such solids are ice; solid hydrogen fluoride (HF); solid ammonia, etc.