The ionic bond occurs between atoms that have different electronegativity: metals and non-metals.
- The nonmetal, more electronegative, with a great capacity to attract and gain electrons to complete its valence shell, will transform into a negative ion, an anion.
- The less electronegative metal, with a great tendency to lose electrons and acquire the most stable configuration, will transform into a cation.
Ionic compounds do not form molecules, but a crystal lattice of attracting positive and negative ions that extends indefinitely. A very orderly structure is formed: the glass.
An example of an ionic compound is sodium chloride.