An Ionic Bond is an electrostatic force of attraction between oppositely charged ions. In a giant ionic crystalline lattice, the oppositely charged ions are packed together in a highly regular way. Ionic Bonding exists in every direction, three-dimensionally throughout the entire crystalline structure. Ionic bonding is not uni-directional. Any particular ion is not associated with just one other. For example, in sodium chloride each Na+ ion is surrounded by six Cl- ions, and each Cl- by six Na+ ions. The separate entity, NaCl, does not exist. The substance is not molecular it is ionic. Relating to their structure, ionic compounds typically are hard and have high melting and boiling points, and they can conduct electricity when their ions are free to move about, as in aqueous solutions and when molten.
The picture below illustrates the sodium chloride crystalline ionic lattice structure. (Sir William Henry Bragg (1862-1942), with his son Sir William Lawrence Bragg, was awarded the Nobel Prize for Physics in 1915 for work using the X-ray spectrometer on the arrangement of particles in crystals.)
See also Covalent Bond | Molecule.