Fundamental to our understanding of the chemical bond are the experimentally measured properties of a bond--its bond length, bond strength, and bond dipole. From bond dipole data we will derive the concept of electronegativity--that some atoms have a greater power to attract electrons than have others.
These ideas will allow us to discover two types of bonding--ionic and covalent. Compounds with large electronegativity differences tend to have unusually strong bonds. This can be rationalized by proposing that an electron is given from the more electropositive atom to the more electronegative one. This situation creates an anion and a cation that are bonded together primarily by electrostatic attraction between the oppositely charged ions. For bonded atoms with similar electronegativities, the sharing of electrons between the nuclei produces a covalent bonding interaction.