Because metallic elements tend to lose electrons and nonmetallic elements tend to gain electrons, a pair of contrasting elements will exchange electrons so that both achieve stable electronic configurations. The resulting ions of opposite charge have a strong force of electrostatic attraction, which is called an ionic bond. Note: This bond forms through the complete transfer of electrons from one atom to another, in contrast to the electron sharing of the covalent bond.
The force of attraction between two points of opposite electrical charge is given by Coulomb's law:
where q + is the positive charge, q – is the negative charge, and d is the distance between the two charges. This law of electrostatic attraction can be used to measure the distance between two spherical ions because the charges can be considered to be located at the center of each sphere. (See Figure 1.)
Figure 1. The distance between ionic charges.