Electrical interaction, ionic

Polarizability (Section 5.4) The measure of the change in a molecule s electron distribution in response to changing electric interactions with solvents or ionic reagents. 

The theory of Debye and Hiickel started from the assumption that strong electrolytes are completely dissociated into ions, which results, however, in electrical interactions between the ions in such a manner that a given ion is surrounded by a spherically symmetrical distribution of other ions mainly of opposite charges, the ionic atmosphere. The nearer to the central ions the higher will be the potential U and the charge density the limit of approach to the central ion is its radius r = a. 

The electrical interactions can be easily calculated when the particle is close to the substrate and the ionic strength is low. In this case, we can simplify the problem to a conventional punctual particle with a charge q placed in the electrical field generated by the substrate in solution [9]. Using the Gouy-Chapman model for the calculation of the electrical field generated by the substrate leads to the following equation ... 

Polar interactions between molecules arise from permanent or Induced dipoles existing in the molecules and do not result from permanent charges as in the case of Ionic interactions. Examples of polar substances having permanent dipoles would be alcohols, ketones, aldehydes etc. Examples of polarizable substances would be aromatic hydrocarbons such as benzene or toluene. It is considered that, when a molecule carrying a permanent dipole comes Into close proximity to a polarizable molecule, the field from the molecule with the permanent dipole induces a dipole in the polarizable molecule and thus electrical interaction can occur. It follows that to selectively retain a polar solute, then the stationary phase must also be polar and contain, perhaps, hydroxyl groups. If the solutes to be separated are strongly polar, then perhaps a polarizable substance such as an aromatic hydrocarbon could be employed as the stationary phase. However, to maintain strong polar interactions with the stationary phase (as opposed to the mobile phase) the mobile phase must be relatively non-polar or dispersive in nature. 

This problem has been discussed in some detail by Orgel et al. [J. S. Griffith and L. E. Orgel, Quart, Rev, London) 11,381 (1967)] in connection with the type of bonding which exists in the complex ions of metals. It turns out that the description covalent or ionic is very dependent on the strength of electrical interaction with the complex-ing group. 

The free energy (G) of a solution containing ions may be regarded as being made up of two parts first, that corresponding to the value for an ideal solution at the same concentration as the ionic solution (Go), and second, an amount due to the electrical interaction of the ions (Gei.) thus... 

Field ionization. The removal of electrons from any species by interaction with a high electrical field. Ionic dissociation. Decomposition of an ion into another ion of lower formula weight, plus one or more neutral species. 

The term [dG/dni f p , i the chemical potential (p ). The electrochemical potential, often denoted as ft , is the corresponding quantity for a system containing ionic charges, where the energy state of one ion depends on both chemical and electrical interactions with solvent molecules and other ions in the system. Guggenheim [5] separated the electrochemical potential of ion species i in phase a into chemical and electrical components ... 

Increasing megnitude of ionic atmosphere ions reduces notation efficiency through increased screening of electrical interactions. 

Unfortunately, like all easy to use principles, the solubility product principle is not generally applicable. At higher concentrations, electrical interactions, complex formation, and solution nonideality make the prediction of the effect of ionic species on the solubility of other ionic species much more complicated. 

Until the advent of quantum mechanics the reasons for the stability of molecules were unknown. The cohesive energy of ionic crystals could be adequately interpreted on the purely classical basis of the electrical attraction of the oppositely charged ions. Some attempts were made to interpret the interaction of all atoms on the basis of the electrical interaction of positive and negative charges, electrical dipoles, induced dipoles, and so on. These classical calculations indicated that the bonding between two like atoms, such as two hydrogen atoms, should be very much weaker than it is. This is another problem that classical physics failed to solve. 

The electrical interaction becomes very important in the case of ionic surfactants. This interaction can be broken down into two contributions (8), i.e. Coulombic and dipole, as follows ... 

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