Attractions between ions

The dominant force in ionic liquids is Coulombic attraction between ions. The Coulombic attraction term is given by Equation (3.1-2) ... 

Am. (ci) An ion is a charged atom or group of atoms an ionic bond is the attraction between ions. 

The melting point of NaCl is 801°C, of CaCl2 is 782°C, and of AICI3 is 190°C. The electrostatic forces of attraction between ions increase with an increase in the charge. In these ionic solids, the charge on the cations Na", Ca ", and Al ... 

The larger the value of e, the smaller the attraction between ions. Water, with t 60. separates ions very welt. Here are some values ofe methanol, 33 ethanol. 24 benzene, 2 vacuum and air, 1. Ionic compounds dissolved in less polar solvents than water may exist predominantly as ion pairs, not separate ions. 

There are several physical properties of a solvent that are of importance in determining its behavior. Two of the most important from a pragmatic point of view are the melting and boiling points. These determine the liquid range and hence the potential range of chemical operations. More fundamental is the permittivity (dielectric constant). A high permittivity is necessary if solutions of ionic substances are 10 form readily. Coulombic attractions between ions are inversely proportional to the permittivity of the medium ... 

The familiar Lewis structure is the simplest bonding model in common use in organic chemistry. It is based on the idea that, at the simplest level, the ionic bonding force arises from the electrostatic attraction between ions of opposite charge, and the covalent bonding force arises from sharing of electron pairs between atoms. 

Giant ionic structure A lattice held together by the electrostatic forces of attraction between ions. 

Since the potential energy of interaction between two ions is proportional to 1 /eT, then the lower the relative permittivity of a solvent, the greater will be the attraction between ions of opposite charge. A similar relation holds for the interaction between an ion and a dipole, and between two dipoles. So solvents of low relative permittivity encourage associative behaviour. 

Although most ionic compounds are soluble in water, some are not very soluble at all. The attraction between ions is difficult to break. As a result, compounds with very strong ionic bonds, such as silver chloride, tend to be less soluble in water than compounds with weak ionic bonds, such as sodium chloride. 

When atoms having greatly differing electronegativities combine, electron transfer occurs and ions are formed. The electrostatic attraction between ions is the essence of ionic bonding. However, the transfer may not be complete, so there is a continuum of bond character from complete covalent (as in H2) to almost completely ionic (as in LiF). 

An attraction between ions of opposite charge. Potassium bro-i mide consists of potassium ions (K ) ionically bound to bro- mide ioas (Br). Unlike covalent i bonds, ionic bond formation involves transfer of electrons,... 

Expansion of the blob. Because of attraction between ions and electrons, expansion of the blob is governed by the law of ambipolar diffusion. As a result out-diffusion of electrons is almost completely suppressed, but the diffusion coefficient of ions is increased by a factor of two. Thus, blob expansion proceeds very slowly and may usually be neglected in the problem of Ps formation. 

One peculiarity of salt (and other substances with atoms locked in a crystalline structure by ionic bonds) is that individual molecules of sodium chloride do not exist at room temperature. What does exist is a lattice of oppositely charged ions, a crystal held together by the strong electrostatic attraction between ions. 

Short-range (<0.5 nm) interactions between ions in solution result in the formation of ion pairs or complexes with other ions or with organic molecules. An ion pair is a transient entity formed by coulombic attraction between ions of opposite charge, with each ion retaining its own water of hydration. In a complex, the ions form covalent or coordinate bonds to form an entity with its own hydration shell. 

Arrays of ions tend to maximize the net electrostatic attraction between ions, while minimizing the repulsive interactions. The former ensures that cations are surrounded by anions, and anions by cations, with the highest possible coordination numbers. In order to reduce repulsive forces, ionic solids maximize the distance between like charges. At the same time, unlike charges cannot be allowed to get too close, or short-range repulsive forces will destabUize the stmcmre. The balance between these competing requirements means that ionic sohds are highly symmetric stmctures with maximized coordination numbers and volumes. 

Which is stronger, the attraction between ions or the attraction... 

The ratio acid / base is the buffer ratio. Because the buffer ratio is not altered by dilution, neither is the pH, except in strong solutions where the attraction between ions becomes sufficiently great to interfere with the simple equilibria. Small additions of acid and alkali alter the buffer ratio and pH very little. Buffering is obviously most efficient when acid (base), i,e, when pH vK-... 

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