The inorganic salt sodium iodide exhibits ionic bonding. An ionic bond is the strongest of the chemical bonds and gives off the most energy when broken. The other types of chemical bonds include covalent and polar covalent bonds, hydrogen bonds, and van der Waal forces.
In an ionic bond, one of the atoms is a strong electron donor and the other atom is a strong electron acceptor. Halogens such as iodine are highly electronegative and take an electron from another atom to fill its outer orbital completely with eight electrons, which is a stable atomic state. Alkali metals such as sodium are strong electron donors with one outer orbital electron.This electron is quickly donated so that the metal's outer orbital also has eight electrons.