Ionic theory

The more recent work finds its origin in the developments in theoretical organic chemistry which occurred after 1930. By means of the electronic theory of G. N. Lewis and by the consistent application of the ionic theory and that of equilibria to organic chemistry, C. K. Ingold and others began to classify the many compounds and reactions according to fundamental principles, a process which is well known to have yielded a rich harvest. 

A base, in terms of the ionic theory, is a substance which yields hydroxy ions as the only negative ion, when dissolved in an ionizing solvent (usually water). The general and characteristic properties of bases are predominantly due to the properties of hydroxy ions. 

The elucidation of the electrical behavior of electrolytes owes much to Arrhenius, who was the originator of the theory of electrolytic dissociation, generally, known as the ionic theory. 

Although the Berzelius ionic theory achieved successes in interpreting inorganic compounds, it met persistent difficulties in the emerging domain of organic chemistry. By about 1860, E. Frankland, F. A. Kekule, and others had developed the opposing concept of valence (and specifically, the quadrivalence of carbon) to... 

Nernst s point of entry into ionic and electronic theories in chemistry, then, was electrolysis and solution theory, in the mainstream of the "Ionist" dissociation theory. Indeed, van t Hoff similarly proposed an ionic theory of the polar molecule in 1895, speculating on the binding forces between 0+ and O- ions in the 02 molecule. 114... 

Lowry is best known to chemistry students through the tradition of eponymony, since the proton theory of acidity is known as the "Bronsted/Lowry theory" of proton donors. His most important experimental investigation likely was a long series of studies on optical rotatory dispersion.49 For our purposes, there is special interest in his discovery of mutarotation in camphor derivatives and his theory of dynamic tautomerism, which led him to an ionic theory of organic reaction mechanisms. 

Thus far, we have not introduced any assumptions about the dissociation of electrolytes in order to describe their experimental behavior. As far as thermodynamics is concerned, such details need not be considered. We can take the limiting law in the form of Equation (19.1) as an experimental fact and derive thermodynamic relationships from it. Nevertheless, in view of the general applicability of the ionic theory, it is desirable to relate our results to that theory. 

The ionic theory thus has the advantage of isolating the quantum and other effects that are difficult to calculate into the potential C/iocai which is treated empirically (Section 3.1). The long-range effects which are important for crystal chemistry are then given by the Madelung term which can be readily calculated using classical electrostatic theory. 

The concept of bond valence, which, as will be shown below, is the same as the bond flux derived in Chapter 2, grew out of attempts to refine Pauling s principles determining the structures of complex ionic crystals (Section 1.7). In this empirical evolution of Pauling s model, both the electrostatic and short-range components were developed simultaneously. Only later did it become apparent that it was also possible to derive the properties of the electrostatic component independently using the ionic theory. 

Ionic theory of caustification.—The explanation offered by the ionic theory runs somewhat as follows At the start, the soln. contains the ions... 

The introduction of carbon dioxide into the solution removes the caustic soda (or, from the point of view of the ionic theory, the OH ions), so that the equilibrium is disturbed and the reaction then proceeds completely from left to right. Similarly, addition of ionised ammonium chloride suppresses the concentration of the OH ions already present in solution more of the pyrovanadate therefore undergoes hydrolysis, in order that the equilibrium concentrations of ions shall be maintained, until all the pyrovanadate is converted into metavanadate. 

The chief merit of the ionic theory is the ease with which quantitative calculations can be performed within a simple electrostatic approach. These will be discussed in Chapter 5. Even if it could be conclusively proven that crystals such as NaCl do not contain ions, chemists would be reluctant to discard the ionic description. The model even has successes-and this should arouse suspicion - in situations where few chemists would seriously entertain the real existence of ions. For example, the 4d and 5d elements tend to exhibit high oxidation states more readily than their counterparts in the 3d series. This can be explained if we note (see Section 4.3) that the energies required to attain highly ionised states are much smaller for the heavier atoms, provided that we are prepared to believe that compounds like WF6, Re03 and 0s04 are ionic ... 

E. Crawford, Arrhenius From Ionic Theory to the Greenhouse Effect, Science History Publications, Canton, MA, 1996. 

Explain the process of neutralization according to the ionic theory, and account for any differences noted in the conductivity. Write the ionic equation. 

Ionization. The electrical conductance of electrolytes is explained in terms of the ionic theory by the presence of independent... 

Until the student has thoroughly mastered the ionic theory, he should write equations in the fully ionized intersecting form for every reaction which he studies. Later, with the practice thus... 

Chapter I is devoted to the quantitative measurements of chemistry — combining ratios, densities, and so forth. Part one may be actually performed in the laboratory or it may be handled with part two entirely in the class room the laboratory work may start with the preparations of Chapters II and IV. Chapter III deals with the ionic theory. The preparation work is interrupted after about the fifth week and the short experiments in ionization are performed in the laboratory. Part two of Chapter III is simultaneously handled in the class room. 

Feb. 19,1859, Wijk, Sweden - Oct. 2,1927, Stockholm, Sweden). Arrhenius developed the theory of dissociation of electrolytes in solutions that was first formulated in his Ph.D. thesis in 1884 Recherches sur la conductibilit galvanique des dectrolytes (Investigations on the galvanic conductivity of electrolytes). The novelty of this theory was based on the assumption that some molecules can be split into ions in aqueous solutions. The - conductivity of the electrolyte solutions was explained by their ionic composition. In an extension of his ionic theory of electrolytes, Arrhenius proposed definitions for acids and bases as compounds that generate hydrogen ions and hydroxyl ions upon dissociation, respectively (- acid-base theories). For the theory of electrolytes Arrhenius was awarded the Nobel Prize for Chemistry in 1903 [i, ii]. He has popularized the theory of electrolyte dissociation with his textbook on electrochemistry [iv]. Arrhenius worked in the laboratories of -> Boltzmann, L.E., -> Kohlrausch, F.W.G.,- Ostwald, F.W. [v]. See also -> Arrhenius equation. 

We may note in passing that the dependence upon covalcncy from the Harrison-Phillips model, a,. — 0.5, does not look very similar to the present a, but does give a reasonable account of experiment. In fact, both arc approximately linear in p over the range of values of that occur. As we have noted about ionicity theories, a finding of linear plots is not compelling evidence for the validity of a model, particularly if a scale parameter is available. 

The basis for the conductivity properties of solutions was first correctly identified by Svante Arrhenius, then a Swedish graduate student in physics, who carried out research on the nature of solutions at the University of Uppsala in the early 1880s. Arrhenius came to believe that the conductivity of solutions arose from the presence of ions, an idea that was at first scorned by the majority of the scientific establishment. However, in the late 1890s when atoms were found to contain charged particles, the ionic theory suddenly made sense and became widely accepted. 

This theory of electrolytic dissociation, or the ionic theory, attracted little attention until 1887 when vanT IIoff s classical paper on the theory of solutions was published. The latter author had shown that the ideal gas law equation, with osmotic pressure in place of gas pressure, was applicable to dilute solutions of non-electrolytes, but that electrolytic solutions showed considerable deviations. For example, the osmotic effect, as measured by depression of the freezing point or in other ways, of hydrochloric acid, alkali chlorides and hydroxides was nearly twice as great as the value to be expected from the gas law equation in some cases, e.g., barium hydroxide, and potassium sulfate and oxalate, the discrepancy was even greater. No explanation of these facts was offered by vanT Iloff, but he introduced an empirical factor i into the gas law equation for electrolytic solutions, thus... 

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