When forces acting between two atoms or groups of atoms lead to the formation of a
stable independent molecular entity, a chemical bond is considered to exist between these
atoms or groups. The principal characteristic of a bond in a molecule is the existence
of a region between the nuclei of constant potential contours that allows the potential
energy to improve substantially by atomic contraction at the expense of only a small
increase in
kinetic energy. Not only directed covalent bonds characteristic of organic compounds, but also bonds
such as those existing between sodium cations and chloride anions in a crystal of
sodium chloride or the bonds binding aluminium to six molecules of water in its environment,
and even weak bonds that link two molecules of
O2
into
O4, are to be attributed to chemical bonds.
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