Characteristics of ionic compounds

Characteristics of ionic compounds

1. Physical state

(i) Electrovalent compounds are generally crystalline in nature.

(ii) These compounds are generally made from ions which are arranged in a regular way as a crystal lattice.

(iii) Force of attraction between the ions is non-directional and extends in all directions.

(iv) Thus electrovalent compounds exist as three dimensional solid aggregates.

(v) Normally each ion is surrounded by a number of oppositely charged ions and this number is called as coordination number

2. High melting and boiling point
(i) Due to strong electrostatic forces of attraction, the ions are held tightly in their position in the crystal lattice.

3. Electrical conductivity
(i) Electrovalent solids do not conduct electricity.

(ii) The reason is that the ions, on account of electrostatic forces of attraction, remain intact occupying fixed positions in the crystal lattice.

(iii) The ions, thus do not move in solid state when electric current is applied.

(iv) When electrovalent compounds are melted or dissolved in a polar solvent, the ions become mobile.

(v) They are attracted towards the respective electrodes and act as carrier of electric current. Thus, electrovalent compounds in the molten state or in solution conduct electricity.

4. Solubility of Ionic compound.

(a) Electrovalent compounds are fairly soluble in polar solvents and insoluble in non-polar solvents.

(b) The polar solvents have high values of dielectric constants.

(c) The solubility of an ionic compound in a polar solvent can also be explained on the basis of lattice energy and hydration energy.

(d) The electrovalent compound dissolves in a solvent if the value of solvation energy is higher than the lattice energy of the electrovalent compound.

(e) These ions are surrounded by solvent molecules. This process is called solvation. This process is exothermic.

(f) The value of solvation energy depends on the relative size of the ions.

(g) Smaller the ion more of solvation, hence solvation energy will be high.