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Georgios
TSAPARLIS
EXCERPTS: One year ago (Vol. 2, No. 2, May 2001), CERAPIE published the first theme issue on structural concepts…. The promise was then given that a second theme issue on the same theme would follow one year later… This Preface should be taken as an addition … to the Preface in last year's theme issue. [(NOTE) Three (additional) papers on structural concepts were included in Issue 3 of Volume 2 (October 2001): Peter G. Nelson's paper was Part 2 of his modified Lewis theory… Rick Toomey, Ed Depierro and Fred Garafalo aimed at helping students at the introductory college level to make inferences about the atomic realm by delaying the presentation of atomic structure. Georgios Tsaparlis studied the physical and mathematical evidence that make the Schroedinger equation plausible, both from the historical perspective and by revieweing and combining various current heuristic introductions to quantum mechanics.] This theme issue contains eleven papers, of which three are invited and eight are reviewed contributions. At the outset, I thank very much all contributors. Pierre Laszlo deals with … the paper tool of reaction mechanisms, taught with Lewis structural formulae, using curved arrows to denote motions of electrons … While this practice improves upon the rational understanding of chemical reactions and their underlying logic, it has many of the features of slang …. Electron-pushing with curved arrows and the VSEPR rationale … ignore that electrons are mobile and delocalised over the entire molecule. … On the other hand, the study of any reaction mechanism is experimental in nature. … The intention of the author is to influence colleagues who teach to non-chemists: "to use mechanistic language on such a public is to do them a disservice because they are not future chemists …". The article by Padeleimon Karafiloglou is in some way relevant to the position paper of Laszlo. It builds bridges between valence bond and molecular orbital theories…. Electron transfer (from bonding to anti-bonding orbitals) effects, as delocalisation and hyperconjugation, are translated into a language referring to resonance structures of covalent and ionic components of bonds…. Georgios Tsaparlis and Georgios Papaphotis report results of a study with twelfth-grade Greek students. (According to their) findings … students did not have a clear understanding of orbitals, and especially their probabilistic rather than deterministic nature. … In addition, they did not realise the approximate nature of atomic orbitals for many-electron atoms…. In two connected papers, Keith S. Taber presents and discusses data relating to student understanding of the orbital concept and related ideas at college level (between secondary and university level). … The first paper describes how students conceptualised key aspects of atomic orbitals. In the subsequent paper, the author considers students' understanding of the molecular orbital concept. … It was found that students often identified the orbitals involved in two-centre bonds as atomic orbitals. … (The) findings suggest that students are not given sufficient time to construct acceptable models of atoms and molecules. Richard K. Coll and Neil Taylor … examine mental models for chemical bonding held by senior secondary students, undergraduates and postgraduates. Using an interview protocol, … (they) found that the learners' mental models were simple and realist in nature, in contrast with the sophisticated and mathematically complex models they were exposed to during instruction. H.-D. Barke and H. Wirbs propose sphere packings and crystal lattices as structural models of inorganic solids… In a research study with students at the eighth grade in Germany, the authors found that students of the treatment group were able to recognise unit cells of cubic structures and to determine empirical formulae from the used models. Jan H. Van Driel reviews a research program … in The Netherlands which aimed to develop 14-15 years-old students' ideas of macroscopic chemical phenomena together with their views of the particulate nature of matter. The program was initiated with the work of Wobbe De Vos… In the first year, students were introduced to the concepts of 'chemical substance' and 'chemical reaction'. In the second year, the program focused on the introduction of the concepts of 'chemical equilibrium' and 'chemical kinetics'. … Students of this age have limited abilities to reason in corpuscular terms. However, there were students who used a simple model of colliding and moving particles to explain chemical phenomena … Peter G. Nelson … draws upon his previous work to propose a progressive teaching of introductory chemistry. … In most current chemistry courses, students are introduced to atoms, molecules, ions, and electrons early in the course, and have to accept the teacher's word that these exist. A better method is to teach chemistry progressively, starting with observations at the macroscopic or bulk level (level one), interpreting these at an atomic and molecular level (level two), and then at an electronic and nuclear level (level three). Ioannis Gerothanassis, Anastassios Troganis, Vassiliki Exarchou, and Climentini Barbarossou present a student-oriented approach, which enhances the ability of students to comprehend the basic concepts of NMR spectroscopy and the NMR spectra of various nuclei…. In addition, a wide range of applications of NMR spectroscopy is presented, including exchange phenomena, structural studies of complex biomolecules, applications to food analysis, clinical studies, and NMR as a microscope and magnetic tomography. (Finally)
Raymond Kapral and Styliani Consta review the classical,
quantum, and mixed quantum-classical theory used for studying chemical
rate constants in condensed phases (bringing us into) … the most
complicated area of theoretical chemistry … the treatment of chemical
kinetics at the electrical level. First they visit the topic of treating
rate coefficients with classical mechanics … There are reactions,
such as the conformational changes of the ammonia molecule ... or proton
and electron transfer processes, where quantum mechanics must be applied.
… On the other hand, there are very important reactions in solution
(especially for biological systems) … that strictly should be treated
quantum mechanically. … This is not practical due to the large
number of degrees of freedom. A mixed approach is then used …
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