Classification of solid on the basis of binding forces

The solids are the substances which have definite shape. In terms of kinetic molecular model, solids have regular order of their constituent particles i.e. atoms, molecules or ions. These particles are held together by fairly strong forces; therefore, they are present at fixed position. The properties of solids not only depend upon the nature of the constituents but also on their arrangements.

Depending on the nature of bonds present in the constituent particles, crystalline solids may be classified into following categories. Namely-

1. Molecular Solids: – The solids in which the constituent particles are molecules. They are held together by weak van der Waal’s force. e.g., ice (hydrogen bonding), H₂, iodine, solid CO₂ Ar, CCl₄, (London forces), HCl, SO₂ (dipole-dipole interaction) etc.
2. Ionic Solids: – These are solids consists of positively and negatively charged ions arranged in a regular fashion throughout the crystals. The ions ate held together by strong electrostatic forces. e.g. salts like Nacl, NaNO₃, LiF, Na₂SO₄, ZnS, CaF₂, MgO, etc.
3. Covalent Solids: – In covalent solids the constituent particles are atoms held together by covalent bonds. e.g. Diamond, silicon carbide (SiC), silica (SiO₂), AlN, etc.
4. Metallic Solids: – In metallic solids the constituent particles are positive kernels immersed in a sea of mobile electrons. The force present between them is metallic bond. For examples, metals such as Cu, Ni, Fe, Ag, Mg, etc.