Ionic bonding is the complete transfer of valence electrons between atoms. It is a type of chemical bond that generates two oppositely charged ions. In ionic bonds, the metal loses electrons to become a positively charged cation, whereas the non-metal accepts those electrons to become a negatively charged anion. Ionic bonds require an electron donor, metal, and an electron acceptor, nonmetal.
Ionic Bonding is observed because metals have few electrons in its outer-most orbital. By losing those electrons, these metals can achieve noble-gas configuration and satisfy the octet rule. Similarly, nonmetals that have close to 8 electrons in its valence shell tend to readily accept electrons to achieve its noble gas configuration. In ionic bonding, more than 1 electron can be donated or received to satisfy the octet rule. The charge on the anion and cation corresponds to the number of electrons donated or received. In ionic bonds, the net charge of the compound must be zero.