Definition: The electrostatic attraction between the cation (+ve ions) and anions (-ve ions) produced by electron transfer constitutes an ionic or electrovalent bond.
Conditions for formation of ionic bond:
(1) Bond formations occur between the metal and nonmetal. Metal is donor and nonmetal is acceptor.
Net lowering of energy(2) Net lowering of energy:
To form a stable ionic compound, there must be a net lowering of the energy. For example- formation of NaCl molecule
(a) Na ― e → Na+ ―119 kcal
(b) Cl + e → Cl‾ +85 kcal
(c) Na+ + Cl‾→ Na+ Cl‾ +187 kcal
Net energy released, 187 + 85 ― 119 = 153 kcal
This causes lowering of energy of the process, hence ionic bond formed.
(3) Electro negativity difference between the atoms
Na → 0.9
Cl → 3.0
Difference, 3.0 ― 0.9 = 2.1
Hence ionic bond will form.
Factors that govern the formation of ionic bond:
(1) Ionization energy,
(2) Electron affinity,
(3) Lattice energy
Some examples of ionic bond:
NaCl
CaO
Characteristics of ionic compounds:
(1) solids at room temperature
(2) high melting and boiling points
(3) hard and brittle,
(4) soluble in water but insoluble in organic solvents,
(5) conductors of electricity,
(6) don’t exhibit isomerism
(7) undergo ionic reactions which are fast.