Pure electrostatic forces

Consider now the case where a = 0, that is to say, where we have pure electrostatic forces, with. /npasses through a maximum at T = d for if we differentiate with respect to T, and set the result equal to zero, we have... 

Most of the solvents involved in the work to be discussed here are oxygenated compounds of the alcohol, ether, ketone, and ester types, nitro compounds, and nitriles, which in general have dielectric constants from around 40 down through 2 or so. From the difference in dielectric constant between these substances and water (Z)25° = 78), it would be expected that cations and anions should pair up more strongly through purely electrostatic forces than in water, and that electrical conductivities should therefore be quite low. Such a lowered conductivity is, in fact, generally found. 

The intermolecular forces of adhesion and cohesion can be loosely classified into three categories quantum mechanical forces, pure electrostatic forces, and polarization forces. Quantum mechanical forces give rise both to covalent bonding and to the exchange interactions that balance tile attractive forces when matter is compressed to the point where outer electron orbits interpenetrate. Pure electrostatic interactions include Coulomb forces between charged ions, permanent dipoles, and quadrupoles. Polarization forces arise from the dipole moments induced in atoms and molecules by the electric fields of nearby charges and other permanent and induced dipoles. 

Chemisorption and Physisorption. One classification of adsorption phenomena is based on the adsorption energy the energy of the adsorbate-surface interaction. In this classification there are two basic types of adsorption chemisorption (an abbreviation of chemical adsorption) and physisorption (an abbreviation of physical adsorption). In chemisorption the chemical attractive forces of adsorption are acting between surface and adsorbate (usually covalent bonds). Thus, there is a chemical combination between the substrate and the adsorbate where electrons are shared and/or transferred. New electronic configurations are formed by this sharing of electrons. In physisorption the physical forces of adsorption, van der Waals or pure electrostatic forces, operate between the surface and the adsorbate there is no electron transfer and no electron sharing. 

It is of importance for a knowledge of the forces acting between colloidal particles that the greatest distance at which the London forces are still important is not the radius of the atom but in fact of the order of magnitude of the radius of the particle itself, since the interaction between all the atoms in each of the colloidal particles must be summed, and this interaction, therefore, will increase with increasing size of the particles (Hamaker)1. This is quite different from, for example, the interaction between particles with a crystal lattice in which only purely electrostatic forces would act in this case the radius of action remains, even for large particles, of the order of the lattice constant and there is only a question of a surface action. The effect of the more deeply situated parts of the lattice does not appear outside on account of the mutual compensation of the action of the oppositely charged ions. 

The type of lattice formed by a particular compound does not necessarily define the character of the bond. Thus, although PbS, PbSe and PbTe crystallize with a sodium chloride type lattice which is normally associated with a purely electrostatic force between the ions, these compounds possess, in some part, the properties of a metal. ... 

Purely electrostatic forces between ions are nondirectional, but with increasing covalent character the directional properties of valence orbitals become more important. Compounds between nonmetallic elements have predominantly covalent bonding and the structures can often be rationalized from the expected CN and bonding geometry of the atoms present (see Topics C2 and C6). Thus in SiC both elements have tetrahedral coordination in Si02 silicon also forms four... 

Most often, the electrostatic bond is between two ions (the ionic bond or salt linkage ). There are variants in which the bond is formed between an ion and a dipole or between two dipoles. They are all maintained by purely electrostatic forces.The ionic bond has a strength of about 5 kcal/mol and declines by the second power of the distance between the opposite charges. Sodium chloride (Na Cl ) is a typical example. In aqueous solution, each ion is able to move about freely so long as it does not leave the field of its counterion in other words, the bond is non-directional and non-rigid. 

It is an instance where the monovalent H atom is linked to two electronegative atoms, to one by means of a pure covalent bond and to the other by purely electrostatic forces called the hydrogen bond. This may be illustrated as follows -... 

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