Definition of Ionic Bond
Electropositive and electronegative chemical elements form an ionic bond due to the transfer of electrons from electropositive to electronegative atom 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 motive of the two elements behind the above reaction.Na: 1s2 2s2 2p6 3s1, Na+: 1s2 2s2 2p6 and Cl: 1s2 2s2 2p6 3s2 3p5, Cl–: 1s2 2s2 2p6 3s2 3p6. An examination of the electronic configuration of Na, Na+, Cl, and Cl– shows both the ions have attained stable noble gas configuration. Therefore, the attainment of a stable noble gas configuration is the clue of 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 most likely to form negative ions.
Characteristics of Ionic Bonding Compounds
The lower the charge on cations the better is the chance for the formation of ionic compounds. Since the lower charge on the cations corresponds to low ionization energy. The larger the size of the metal atom or ion favor for the formation of ionic compounds. Since an increase in size associated with the decree of ionization energy. Small size and low charge on the anions will favor the formation of ionic compounds. These factors 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.