Introduction of Ionic Bond
Ionic bond is a kind of chemical bond which involves an electrostatic attraction between two oppositely charged ions because of the complete transfer of valence electrons between them. As for example: metals such as sodium losses electrons to to become positive ion, whereas non-metal such as chlorine accepts electrons to become a negative ion. The metal that gives electrons is called donor and the non-metal that accepts electrons is called acceptor.
Ionic bond occurs between metals and non-metals because the metals have only few electrons in its outermost shell. Thus it likes to give away these electron to achieve the noble gas configuration and satisfy the octet rule. The number of electrons, a metal loses is the number of positive charge it achieves to form the ionic bond.
On other hand to fulfill the octet rule, non metals accepts the electrons and charged negatively. The number of electrons it accepts, is the number of negative charge it gains. As a result an electrostatic force occurs between these two oppositely and equally charged atoms to form an ionic bond.
Sodium losses an electron to get positive charge and chlorine accepts that electron to achieve a negative charge. An electrostatic force holds these to atoms to together in a crystallographic lattice. Thus sodium chloride is formed.
Another example of ionic bond is the formation of magnesium chloride by transferring two electrons from a magnesium atom to two chlorine atoms.
Mg + Cl2 → Mg2+ + 2Cl– → MgCl2
Stability of ionic compound
Stability of an ionic compound depends on:
- The ionization energy
- Electron affinity
- The lattice energy
The ionization energy (IE)
The ionization energy is the energy required to remove a valence electron from the outermost shell of a metal atom. This required energy should be low to form an ionic bond.
A + IE → A+ + e–
Electron Affinity (EA)
Electron affinity (EA) is the energy released when an electron is added to a neutral atom in its gaseous state. To form an ionic bond, the electron affinity of a non metal atom should be high. So that the atom will have more tendency to accept the electron to release more energy to the nature and to become more stable ionic compound.
Lattice Energy (LE)
To form ionic compound the lattice energy should be high.
The difference in electronegativity between the metal and non metal should be high enough to form an ionic compound. For example, the electronegativity of Sodium and chlorine in sodium chloride is:
Na = 0.9 and Cl = 3.0.
Properties of ionic bond
Ionic bond has a very characteristic properties which can differentiate them from the covalent bond.
- Ionic bonds are polar in nature.
- Ionic bond is stronger than covalent bond.
- Compounds with ionic bonds are mostly solid at room temperature.
- Solid compounds with ionic bonds form lattice structure.
- It has high melting point and boiling point.
- Ionic compounds can conduct electricity only when it is melted or in aqueous solution.
- These are soluble in water and other polar solvent.
- They are not soluble in any non polar solvent.
- Ionic compounds are not reactive in its solid state.
- Ionic compounds show ionic reactions in aqueous solution.
- It is very reactive to other ionic compounds in aqueous solution.