What is Ionic Bonding?
Ionic bonding is the electrostatic force that binds together oppositely charged ions formed by the transfer of electron or electrons from an electropositive metal to an electronegative non-metal atom. We know that sodium and chlorine react vigorously to yield crystalline solid sodium chloride. The crystallographic study suggests that there is no single sodium chloride molecule in the NaCl crystal lattice. Each sodium ion is surrounded by six chloride ions in a non-ending pattern by electrostatic forces of attraction or ionic bonding.
Every halogen atom has seven electrons in its outermost orbital and needs one electron to attain a stable electronic configuration of the nearest noble gas. On the other hand, every alkali metal has one electron in the outermost orbital and tries to attain a stable electronic configuration by losing one electron. Therefore, they are combing by the electrostatic force of attraction to form the ionic compounds like NaCl, KCl, NaBr, KBr, etc. The formation of an ionic compound like NaCl by chemical bonding between the sodium atom and chlorine atom is given below the picture.
Examples of Ionic Bonds
Similar types of ionic bonds are also formed in molecules like calcium chloride (CaCl2), calcium oxide (CaO), magnesium sulfide (MgS), magnesium nitride (Mg3N2), aluminum oxide (Al2O3). For example, in calcium chloride, calcium oxide, magnesium sulfide two electrons transfer occurs for the formation of ionic bonding. In such a combination, every participant atom would attain the stable inert gas electronic structure. Therefore, the chemical bond with the transfer of electrons between the participant’s atom is named ionic bonding.
Formation of Ionic Compounds
Attainment of stable noble gas electronic configuration is the clue of formation ionic and covalent bonding or chemical reactions. Such a conclusion helps us to predict the chemical elements which most likely to form ionic compounds. The elements which have low ionization energy are the best candidates for forming positive ions or cations. Similarly, the elements which have high electron affinity are most likely to form negative ions or anions.
The large size of the metal atom or ion is favored for the formation of ionic compounds because with the increasing atomic size ionization energy decreases. Again the small size and low charge on the anions will be favored for the formation of ionic compounds because these factors increase the electron affinity or electronegativity of the atom. The unexpected result is sometimes observed. For example, the second electron affinity of oxygen is negative but it forms ionic bonding or compounds with alkalis or alkaline earth metals.