Introduction to Ionic Bonding: graphic 151ionc.Gif

Ionic bonding is best treated using a simple electrostatic model . The electrostatic model is simply an application of the charge principles that opposite charges attract and similar charges repel. An ionic compound results from the interaction of a positive and negative ion, such as sodium and chloride in common salt.

The IONIC BOND results as a balance between the force of attraction between opposite plus and minus charges of the ions and the force of repulsion between similar negative charges in the electron clouds. In crystalline compounds this net balance of forces is called the LATTICE ENERGY. Lattice energy is the energy released in the formation of an ionic compound.

DEFINITION: The formation of an IONIC BOND is the result of the transfer of one or more electrons from a metal onto a non-metal.

Metals, with only a few electrons in the outer energy level, tend to lose electrons most readily. The energy required to remove an electron from a neutral atom is called the IONIZATION POTENTIAL.

Energy + Metal Atom ---> Metal (+) ion + e-

Non-metals, which lack only one or two electrons in the outer energy level have little tendency to lose electrons - the ionization potential would be very high. Instead non-metals have a tendency to gain electrons. The ELECTRON AFFINITY is the energy given off by an atom when it gains electrons.

Non-metal Atom + e- --- Non-metal (-) ion + energy

The energy required to produce positive ions (ionization potential) is roughly balanced by the energy given off to produce negative ions (electron affinity). The energy released by the net force of attraction by the ions provides the overall stabilizing energy of the compound.
Review formation of Ionic Compounds
Comparison of Ionic, Polar and Non-Polar Bonding