Modern Physical Chemistry: A Molecular Approach (Duffey, George H.)

Aug 8, 2001 - chemistry texts followed the venerable Getman–Daniels–. Alberty–Silbey series (remarkably still being published)— chemical equil...
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Book & Media Reviews Modern Physical Chemistry: A Molecular Approach by George H. Duffey Kluwer Academic/Plenum: New York, 2000. 554 pp. ISBN 0-306-46395-4. $85.00. reviewed by John P. Ranck

The title of this text, Modern Physical Chemistry: A Molecular Approach, is misleading and bears comment. Throughout most of the 20th century, the content and style of physical chemistry texts followed the venerable Getman–Daniels– Alberty–Silbey series (remarkably still being published)— chemical equilibrium based upon classical thermodynamics together with mathematical treatments of electrochemistry, reaction kinetics, and other instrumentally measurable (hence “physical”) phenomena. In the middle of the century, arcane topics such as molecular parachor yielded to atomic spectroscopy and the Bohr theory, and in the latter part of the century, more and more quantum theory was simply grafted onto an essentially unchanged classical thermodynamics text. In the early 1960s, several new and fresh physical chemistry texts appeared, one of these being Professor Duffey’s (1). The one among these new texts that was notable for its dramatic change of style was Gordon Barrow’s (2), which could well have been titled “A Molecular Interpretation (or Explanation) of Chemistry”. Now that Ostwald and Mach are dead and scientists may (and really do) believe in the existence atoms and molecules, the 21st century cries for a new breed of texts that develop a coherent theory of chemistry deriving from the properties of atoms and molecules (rather than merely explaining them), texts willing to abandon heat engines and 19th century equilibrium theory of macroscopic systems in favor of statistical distributions among quantum energy levels—a truly molecular approach to chemical theory—synthesis and construction rather than description and analysis. Despite its title, this is not such a text! It is very much a continuation of mid-20th century tradition. Among the texts with which I am familiar, only that by McQuarrie and Simon (3) is of this new genre. Duffey’s book, however, should be judged on what it is rather than what it purports to be. As for content and order, it begins strangely with chapters on crystals and molecular beams, followed by a chapter on gases that begins with molecules and proceeds to gas laws (the molecular approach?). These chapters are more phenomenology than principles. Five chapters on thermodynamics and phase equilibria and one on electrochemistry complete the first half of the text. The second half contains three chapters on quantum mechanics and spectroscopy (translation, rotation, vibration), one chapter on symmetry and group theory, and one altogether too short and strangely truncated chapter on electronic structure of molecules. The text concludes with three rather classical chapters on kinetics and mechanisms interspersed with one on statistical thermodynamics and a final chapter on photochemistry. Unlike the “Examples” in many texts, the ones in this 1024

book are not gratuitously chosen illustrative examples, but are really well-considered mathematical developments integral to the text. Each chapter concludes with a series of one-sentence Questions (e.g., How is Y …?, Show how Y …?), a number of rather direct Problems, which reinforce algorithmic problem solving rather than provoke thinking, and a list of References to advanced texts together with a well-selected list of recent articles, most from the Journal of Chemical Education or the American Journal of Physics, which students should find very readable and helpful The use of drawings and diagrams is altogether too sparse. There are no graphs accompanying the discussion of Maxwell’s distribution law or blackbody radiation. The angular state functions are presented by the conventional shaded isosurfaces, but the radial state functions for the hydrogen atom are presented as equations only. The only molecular orbitals in sight are in cross-sectional line drawings in a separated-atom united-atom correlation table; even π-bonding in benzene is presented entirely in classical Dewar structures except for one hexagon with a circle drawn in it. There is essentially no historical or biographical information. Physical chemistry is constructed formally rather than derived from experiments conducted by real people. The book has some major idiosyncrasies. For example, an ideal gas is defined as “a phase where the volume of the molecules and the attractions among them are negligible” rather than one adhering to Charles’s and Boyle’s laws. The second law of thermodynamics is derived from Caratheodory’s principle, an elegant formalism that many will judge to be unnecessarily rigorous and perhaps even confusing. Quantum mechanics is based not upon experiment (blackbody radiation, atomic spectra, etc.), but upon a highly formal argument: “Instead of associating all the uncertainties in position, velocity, and momentum with the errors in measurement, considering an irreducible part of them to be an essential attribute of a particle leads to a viable theory.” Quantization of motion is developed as “rectangularly symmetric free motion” where “periodic boundary conditions are said to prevail.” States of Molecular Electrons is probably the most unsatisfactory chapter of all. Beyond the hydrogen molecule ion and homonuclear diatomic molecular orbitals, the hydrogen molecule is discussed in one five-sentence paragraph, which introduces (i) average field of the other electron, (ii) no net charge and effect on HAA and HAB with variation in R, (iii) interelectron correlation, and (iv) configuration interaction. The final sentence of the paragraph dispatches all other homonuclear diatomic molecules. The immediately following section devotes 4 pages to symmetric three-center bonds. Multicenter molecular orbitals (LCAO) beyond the symmetric three-center bonds are restricted to π-bonding in benzene. Bonding between two nonequivalent atoms is treated in a later section in less than two pages in which the definition of Mulliken electronegativity and the differences between semiempirical and ab initio calculations are presented in five sentences. I shall describe this text stylistically, by placing it in a space of five nearly orthogonal dimensions: practical–theoretical; conversational–formal; casual–rigorous; lucid–obscure; terse–

Journal of Chemical Education • Vol. 78 No. 8 August 2001 •

Chemical Education Today

verbose. It is completely theoretical, strictly formal, moderately rigorous, neither lucid nor obscure (neutral), and terse to the point of being dense (not a pejorative). In his preface, Duffey declares: “Its style is simple, concise, and straightforward. Concepts are not hidden in a blizzard of words.” In fact, the sentences, paragraphs, sections, and chapters are all terse (e.g., particle in a box, partition functions, the error function, and the Fermi level all are introduced for the first time in less than eight pages in three successive sections of the “Basic Quantum Mechanics” chapter). Well-prepared physics and mathematics majors at a major university in the 1950s might have appreciated such a tight, complete, formal, sometimes idiosyncratic, moderately rigorous development that stands on its own, but it will be a hard sell to today’s students who demand a more approachable style that relates the material at hand to knowledge and human endeavors in other fields and builds systematically upon methods from standard prerequisite courses. Nor will many of today’s “chemistry and chemical physics majors in their junior or senior years” (for whom the book was designed) recall “the action in an operating vacuum tube”, immediately grasp that “in Newtonian mechanics, the relative movement of two particles…is modeled by a single particle of mass µ =

mAmB/(mA + mB) at the distance r from the origin”, or recognize Laplace’s equation. After examining content, depth, organization, and style, the final question ought to be “Would I (or a student) be drawn to physical chemistry by this text?” Regrettably, the answer is “no”. Prose such as “A continuous manifold of states of a uniform system is generated from a given state by reversible adiabatic processes. In the space of the independent variables, this manifold forms a surface” just does not draw one in. It simply requires too much effort to decipher the terse, formal prose to begin to understand what the author is trying to convey. The text has been carefully edited; I found no mathematical or typographical errors. Literature Cited 1. Duffey, G. H. Physical Chemistry; McGraw-Hill: New York, 1962. 2. Barrow, G. M. Physical Chemistry; McGraw-Hill: New York, 1961. 3. McQuarrie, D. A.; Simon, J. D. Physical Chemistry: A Molecular Approach; University Science Books: Sausalito, CA, 1997.

John P. Ranck is in the Department of Chemistry, Elizabethtown College, Elizabethtown, PA 17022; [email protected]. • Vol. 78 No. 8 August 2001 • Journal of Chemical Education