What is Ionic Bond?
Ionic bond is formed between Electropositive and electronegative chemical elements due to the transfer of electrons from electropositive to electronegative atoms forming ions that are bound by strong electrostatic forces to form ionic compounds.
The ionic bond is defined as the electrostatic forces that bind together oppositely charged ions formed by the transfer of electrons or electrons from an electropositive metal to the electronegative non-metal atom.
Formation of Ionic Compounds
Let us consider the ionic bonding between sodium and chlorine atom.
The electronic configuration of sodium: 1s22s22p63s1
After losing one valence electron the electronic configuration of the sodium ion (Na+) is 1s22s22p6
The electronic configuration of chlorine: 1s22s22p63s23p5
After gaining one valence electron the electronic configuration of the chloride ion (Cl−) is 1s22s22p6
An examination shows that of the electronic configuration of Na+ and Cl− ions is a stable noble gas configuration. Therefore, the attainment of a stable noble gas configuration is the clue to this chemical bond.
Such a conclusion predicts which elements are most likely to form ionic compounds. Thus the elements which have low ionization energy are the best candidate for forming positive ions. Similarly, the elements which have high electron affinity are most likely to form negative ions.
Characteristics of Ionic Bonding Compounds
The lower the charge on cations the better the chance for the formation of ionic compounds. Since the lower charge on the cations corresponds to low ionization energy.
The larger size of the metal atom or ion favors the formation of ionic compounds. Since an increase in size is associated with the decree of ionization energy.
Small size and low charge on the anions will favor the formation of ionic compounds. These factors are also associated with increases in electron affinity and electronegativity.
The above discussion has given us a rough guide for the polarity of ionic compounds. But unexpected result sometimes observes. The second electron affinity of oxygen is negative but it forms a stable ionic compound with alkali and alkaline earth metals.