The bond concept is a human invention. The bond represents a quantity of energy obtained from the overall molecular energy of the compound. The bond theory was conceived by American chemists G.N. Lewis and Linus Pauling. Ionic Bonding - electrostatic attraction between ions of opposite charge. Electrons are transferred between atoms.
Elements form electron configurations of noble gases .
Cation is smaller than the corresponding metal atom because the excess of protons in the ion draws the outer electrons in closer to the nucleus. The extra electron in the anion adds to the repulsion between outer electrons. Also, the added negative charge dilutes the nuclear charge onto more electrons, weakening its effect. In the example above Cl - is larger than Cl. When ionic compounds are formed from the elements, the reaction is always exothermic.