Coulomb between bond charges

Were we to simply add the ionization energy of sodium (496 kJ/mol) and the electron affin ity of chlorine (—349 kJ/mol) we would conclude that the overall process is endothermic with AH° = +147 kJ/mol The energy liberated by adding an electron to chlorine is msuf ficient to override the energy required to remove an electron from sodium This analysis however fails to consider the force of attraction between the oppositely charged ions Na" and Cl which exceeds 500 kJ/mol and is more than sufficient to make the overall process exothermic Attractive forces between oppositely charged particles are termed electrostatic, or coulombic, attractions and are what we mean by an ionic bond between two atoms... 

In this context it is noteworthy to refer to the unsaturated analogue l,2-di(9-anthryl)ethene [32] (Weitzel and Mullen, 1990 Weitzel et al., 1990). Like [6] (Becker et al., 1991), compound [32] forms a stable dianion and tetra-anion upon reduction. In the cyclic voltammogram of [32], the first two electrons are transferred at nearly the same potential, pointing to an effective minimization of the Coulombic repulsion between the charged anthryl units (Bohnen et al, 1992). This situation, which again corresponds to that in [6], could imply a torsion about the central olefinic bond (Bock et al., 1989). 

For two polar molecules arranged as in Fig. la, the attractions between opposite charges exceed the repulsions between like charges. This statement may (if necessary) be confirmed by a simple Coulombs s Law calculation based on the bond-lengths and van der Waals contact specified in the diagram. The total force will be the difference between attraction and repulsion ... 

The energy required for the formation of ionic bonds is supplied largely by the coulombic attraction between oppositely charged ions the ionic model is a good description of bonding between nonmetals and metals, particularly metals from the s block. 

Analogical molecular structure is possessed by other simple compounds such as potassium iodide, ammonium chloride, sodium hydroxide, barium nitrate, ammonium acetate and so on. In all these compounds there is a transfer of one or several electrons from one element to the other, positive and negative ions being thus formed, that are hold together in a crystal by electrostatic attraction. A bond of this kind is no genuine chemical bond in tbe correct meaning of the term, but is just,a result of Coulomb forces of attraction between opposite charges. 

Today, an ionic bond is recognized as the nondirectional electrostatic attraction between oppositely charged ions. For an isolated ion pair, the Coulomb potential energy, U, is simply... 

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