DOCSLIB.ORG

Valence Bond Theory—Its Birth, Struggles with Molecular Orbital Theory, Its Present State and Future Prospects

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Valence Bond Theory—Its Birth, Struggles with Molecular Orbital Theory, Its Present State and Future Prospects molecules Review Valence Bond Theory—Its Birth, Struggles with Molecular Orbital Theory, Its Present State and Future Prospects Sason Shaik 1,* , David Danovich 1 and Philippe C. Hiberty 2,* 1 Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel; [email protected] 2 CNRS, Institut de Chimie Physique UMR8000, Université Paris-Saclay, 91405 Orsay, France * Correspondence: [email protected] (S.S.); [email protected] (P.C.H.) Abstract: This essay describes the successive births of valence bond (VB) theory during 1916–1931. The alternative molecular orbital (MO) theory was born in the late 1920s. The presence of two seemingly different descriptions of molecules by the two theories led to struggles between the main proponents, Linus Pauling and Robert Mulliken, and their supporters. Until the 1950s, VB theory was dominant, and then it was eclipsed by MO theory. The struggles will be discussed, as well as the new dawn of VB theory, and its future. Keywords: valence bond; molecular orbital; Lewis; electron-pair bonds; Pauling; Mulliken; Hund; Hückel 1. Introduction Citation: Shaik, S.; Danovich, D.; This essay tells briefly a story of the emerging two major quantum mechanical theories, Hiberty, P.C. Valence Bond valence bond (VB) theory and molecular orbital (MO) theory, which look as two different Theory—Its Birth, Struggles with descriptions of the same reality, but are actually not. We discuss the struggles between Molecular Orbital Theory, Its Present the two main groups of followers of Pauling and Mulliken, and the ups and downs in the State and Future Prospects. Molecules popularity of the two methods among chemists, and then the fall of VB theory only to be 2021, 26, 1624. https://doi.org/ revived and to flourish. We end the story with the description of the renaissance in modern 10.3390/molecules26061624 VB theory, its current state and its future outlook. The grassroots of Valence Bond (VB) theory date back to the second decade of the 20th Academic Editor: Steve Scheiner century, when Lewis published his seminal paper entitled, “The Atom and The Molecule”[1]. Lewis made use of the discovery of the electron as a fundamental particle of matter, while Received: 19 February 2021 interjecting his command of chemical facts. These led him to conclude that the most Accepted: 10 March 2021 abundant compounds are those which possess an even number of electrons. He therefore Published: 15 March 2021 formulated the “quantum unit of chemical bonding”, an electron pair that glues atoms of most known molecular matter. In so doing, he was brilliantly able to derive electronic structure Publisher’s Note: MDPI stays neutral cartoons that are used to this day and age for teaching and as means of communication with regard to jurisdictional claims in among chemists. Lewis further distinguished between shared (covalent), ionic bonds, and published maps and institutional affil- iations. polar bonds. He also laid foundations for resonance theory, and used it to explain for the first time color in molecules. He even discussed geometry in terms akin to the valence-shell electron pair repulsion (VSEPR) approach [2]. The contribution of Lewis, and its implementation in 1927–1928 into quantum mechan- ics by Heitler and London [3–5], reached Pauling, who was then in Europe in a mission Copyright: © 2021 by the authors. to learn the new quantum mechanics (and bring it back to the USA). Pauling was excited. Licensee MDPI, Basel, Switzerland. He dropped all the previous mechanical models, which he used to teach [6] and began a This article is an open access article wide-ranging program of this theory which he called valence bond theory, and which he distributed under the terms and conditions of the Creative Commons summarized in his monograph [7]. Pauling’s work translated Lewis’ ideas to quantum Attribution (CC BY) license (https:// mechanics, and the work received very high attention and became extremely popular creativecommons.org/licenses/by/ among chemists. 4.0/). Molecules 2021, 26, 1624. https://doi.org/10.3390/molecules26061624 https://www.mdpi.com/journal/molecules Molecules 2021, 26, x FOR PEER REVIEW 2 of 24 Molecules 2021, 26, 1624 2 of 24 Molecular orbital (MO) theory was developed at the same time by Hund and Mulli- ken [8–13], and served initially as a conceptual framework in spectroscopy. Somewhat later,Molecular Lennard-Jones orbital and (MO) Hückel theory applied was developedMO theory atto theelectronic same time structures by Hund of molecules and Mul- [14liken–17 [].8 –13], and served initially as a conceptual framework in spectroscopy. Some- whatSoon later, enough Lennard-Jones the two theories and Hückel and their applied major MO proponents theory to started electronic a struggle structures to dom- of inatemolecules the conceptual [14–17]. frame of chemistry. Initially, MO theory was not accepted too easily by chemists,Soon enough and until the twothe late theories 1950s, and VB their theory major which proponents used a chemical started a language struggle towas domi- up. Subsequently,nate the conceptual MO theory frame was of chemistry. implemented Initially, in useful MO theorysemi-empirical was not programs, accepted too and easily was graduallyby chemists, popularized and until theby eloquent late 1950s, proponents VB theory like which Coulson used a[18], chemical Dewar language [19], and wasothers. up. TheseSubsequently, developments MO theory and the was consequences implemented of in the useful VB– semi-empiricalMO struggle, on programs, the reputation and was of VBgradually theory, popularized determined byits eloquentgradual proponentsdownfall. However, like Coulson with [18 the], Dewardevelopments [19], and of others. new conceptualThese developments frames and and new the computational consequences methods of the VB–MO during struggle,the 1970s ononwards the reputation, VB theory of beganVB theory, to enjoy determined a renaissance its gradual and reoccupy downfall. its place However, alongside with MO the theory developments and DFT. of new conceptual frames and new computational methods during the 1970s onwards, VB theory 2.began The toRoots enjoy and a renaissance Development and of reoccupy VB Theory its place alongside MO theory and DFT. 2. TheLewi Rootss’ formulation and Development of the nature of VB of Theory the chemical bond is in many ways the precursor of VB theory. Lewis’ paper, “The Atom and The Molecule” [1], contains plenty of ideas, some Lewis’ formulation of the nature of the chemical bond is in many ways the precursor of of which were later embedded into VB theory. His electron-pair model and its dynamic VB theory. Lewis’ paper, “The Atom and The Molecule”[1], contains plenty of ideas, some of nature regarding polarity, was formulated 11 years before the onset of VB theory in phys- which were later embedded into VB theory. His electron-pair model and its dynamic nature ics [2]. Moreover, his work was portable and instrumental for the emergence of the new regarding polarity, was formulated 11 years before the onset of VB theory in physics [2]. VB theory of bonding in the hands of Pauling and Slater [2]. It is appropriate, therefore, Moreover, his work was portable and instrumental for the emergence of the new VB theory to begin this section by briefly describing Lewis’ contribution to the nature of the chemical of bonding in the hands of Pauling and Slater [2]. It is appropriate, therefore, to begin this bond.section by briefly describing Lewis’ contribution to the nature of the chemical bond. 2.1. The The Lewis Lewis Electronic Electronic Cubes and Electron Pair Bonds While Lewis f formulatedormulated the electron electron-pair-pair bonds, he also tried to relate these bonds toto the experience of the practicing chemists in the communities of inorganic and organic chemistries [1,20]. [1,20]. In In broad broad terms, terms, the the inorganic chemists were observing chemistry of charged s speciespecies (ions in today’s language), or molecules undergoing dissociation to ions (like acids), while the organic chemists did did not observe much much of of an ionic chemistry, and were interested in the “structure” of their compounds [[2,21,22]2,21,22].. The term “structure” waswas abstract in those early days (mid 19th19th century), and its representations lumped together groups of atom (which appear in many many molecules) molecules) and were were odd odd-looking-looking in modern terms (e.g.(e.g.,, the initial sausages model of benzene by KekulKekuléé [[21,23]21,23]).). Nevertheless, this was the chemical landscape which Lewis tried to describe in terms of bonds between atoms. The first first model model in in the the key key Lewis Lewis paper paper [1] [1 is] isitself itself quite quite cumbersome cumbersome and and is based is based on hison hisrepresentation representation of the of atom the atom as a ascube a cube with witha valence a valence-shell-shell that may that cont mayain contain up to upeight to electronseight electrons (later (laterto be tocalled be called the Octet the Octet Rule) Rule) placed placed at the at corners the corners of the of thecube cube—a—a model model he hadhe had developed developed already already in 1902 in 1902 [24]. [Figure24]. Figure 1 describes1 describes how howLewis Lewis viewed viewed the three the threeputa- tiveputative states states of a single of a single bond bondin the in molecule the molecule like dihalogen like dihalogen underunder different different conditions conditions using theusing cubic the model. cubic model. His view His of view the bond of the is bond dynamic is dynamic and he andis aware he is that aware a bond that can a bond change can itschange character its character in different in different environment environmentss and depending and depending on the nature on the of nature the atoms.
Load more

Recommended publications
  • More Insight in Multiple Bonding with Valence Bond Theory K
    More insight in multiple bonding with valence bond theory K. Hendrickx, B. Braida, P. Bultinck, P.C. Hiberty To cite this version: K. Hendrickx, B. Braida, P. Bultinck, P.C. Hiberty. More insight in multiple bonding with va- lence bond theory. Computational and Theoretical Chemistry, Elsevier, 2015, 1053, pp.180–188. 10.1016/j.comptc.2014.09.007. hal-01627698 HAL Id: hal-01627698 https://hal.archives-ouvertes.fr/hal-01627698 Submitted on 21 Nov 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. More insight in multiple bonding with valence bond theory ⇑ ⇑ K. Hendrickx a,b,c, B. Braida a,b, , P. Bultinck c, P.C. Hiberty d, a Sorbonne Universités, UPMC Univ Paris 06, UMR 7616, LCT, F-75005 Paris, France b CNRS, UMR 7616, LCT, F-75005 Paris, France c Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281 (S3), 9000 Gent, Belgium d Laboratoire de Chimie Physique, UMR CNRS 8000, Groupe de Chimie Théorique, Université de Paris-Sud, 91405 Orsay Cédex, France abstract An original procedure is proposed, based on valence bond theory, to calculate accurate dissociation ener- gies for multiply bonded molecules, while always dealing with extremely compact wave functions involving three valence bond structures at most.
    [Show full text]
  • Theoretical Methods That Help Understanding the Structure and Reactivity of Gas Phase Ions
    International Journal of Mass Spectrometry 240 (2005) 37–99 Review Theoretical methods that help understanding the structure and reactivity of gas phase ions J.M. Merceroa, J.M. Matxaina, X. Lopeza, D.M. Yorkb, A. Largoc, L.A. Erikssond,e, J.M. Ugaldea,∗ a Kimika Fakultatea, Euskal Herriko Unibertsitatea, P.K. 1072, 20080 Donostia, Euskadi, Spain b Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN 55455-0431, USA c Departamento de Qu´ımica-F´ısica, Universidad de Valladolid, Prado de la Magdalena, 47005 Valladolid, Spain d Department of Cell and Molecular Biology, Box 596, Uppsala University, 751 24 Uppsala, Sweden e Department of Natural Sciences, Orebro¨ University, 701 82 Orebro,¨ Sweden Received 27 May 2004; accepted 14 September 2004 Available online 25 November 2004 Abstract The methods of the quantum electronic structure theory are reviewed and their implementation for the gas phase chemistry emphasized. Ab initio molecular orbital theory, density functional theory, quantum Monte Carlo theory and the methods to calculate the rate of complex chemical reactions in the gas phase are considered. Relativistic effects, other than the spin–orbit coupling effects, have not been considered. Rather than write down the main equations without further comments on how they were obtained, we provide the reader with essentials of the background on which the theory has been developed and the equations derived. We committed ourselves to place equations in their own proper perspective, so that the reader can appreciate more profoundly the subtleties of the theory underlying the equations themselves. Finally, a number of examples that illustrate the application of the theory are presented and discussed.
    [Show full text]
  • Theory and Technique
    Lawrence Berkeley National Laboratory Lawrence Berkeley National Laboratory Title COMPUTATIONAL METHODS FOR MOLEUCLAR STRUCTURE DETERMINATION: THEORY AND TECHNIQUE Permalink https://escholarship.org/uc/item/3b7795px Author Lester, W.A. Publication Date 1980-03-14 Peer reviewed eScholarship.org Powered by the California Digital Library University of California CONTENTS Foreword v List of Invited Speakers vii Workshop Participants viii LECTURES 1 Introduction to Computational Quantum Chemistry Ernest R. Davidson 1-1 2/3 Introduction to SCF Theory Ernest R. Davidson 2/3-1 4 Semi-Empirical SCF Theory Michael C. Zerner 4-1 5 An Introduction to Some Semi-Empirical and Approximate Molecular Orbital Methods Miehael C. Zerner 5-1 6/7 Ab Initio Hartree Fock John A. Pople 6/7-1 8 SCF Properties Ernest R. Davidson 8-1 9/10 Generalized Valence Bond William A, Goddard, III 9/10-1 11 Open Shell KF and MCSCF Theory Ernest R. Davidson 11-1 12 Some Semi-Empirical Approaches to Electron Correlation Miahael C. Zerner 12-1 13 Configuration Interaction Method Ernest R. Davidson 13-1 14 Geometry Optimization of Large Systems Michael C. Zerner 14-1 15 MCSCF Calculations: Results Boaen Liu 15-1 lfi/18 Empirical Potentials, Semi-Empirical Potentials, and Molecular Mechanics Norman L. Allinger 16/18-1 iv 17 CI Calculations: Results Bowen Liu 17-1 19 Computational Quantum Chemistry: Future Outlook Ernest R. Davidson 19-1 V FOREWORD The National Resource for Computation in Chemistry (NRCC) was established as a Division of Lawrence Berkeley Laboratory (LBL) in October 1977. The functions of the NRCC may be broadly categorized as follows: (1) to make information on existing and developing computa­ tional methodologies available to all segments of the chemistry community, (2) to make state-of-the-art computational facilities (both hardware and software] accessible to the chemistry community, and (3) to foster research and development of new computational methods for application to chemical problems.
    [Show full text]
  • An Experimental Chemist's Guide to Ab Initio Quantum Chemistry
    J. Phys. Chem. 1991, 95, 1017-1029 1017 FEATURE ARTICLE An Experimental Chemist’s Guide to ab Initio Quantum Chemistry Jack Simons Chemistry Department, University of Utah, Salt Lake City, Utah 84112 (Received: October 5, 1990) This article is not intended to provide a cutting edge, state-of-the-art review of ab initio quantum chemistry. Nor does it offer a shopping list of estimates for the accuracies of its various approaches. Unfortunately, quantum chemistry is not mature or reliable enough to make such an evaluation generally possible. Rather, this article introduces the essential concepts of quantum chemistry and the computationalfeatures that differ among commonly used methods. It is intended as a guide for those who are not conversant with the jargon of ab initio quantum chemistry but who are interested in making use of these tools. In sections I-IV, readers are provided overviews of (i) the objectives and terminology of the field, (ii) the reasons underlying the often disappointing accuracy of present methods, (iii) and the meaning of orbitals, configurations, and electron correlation. The content of sections V and VI is intended to serve as reference material in which the computational tools of ab initio quantum chemistry are overviewed. In these sections, the Hartree-Fock (HF), configuration interaction (CI), multiconfigurational self-consistent field (MCSCF), Maller-Plesset perturbation theory (MPPT), coupled-cluster (CC), and density functional methods such as X, are introduced. The strengths and weaknesses of these methods as well as the computational steps involved in their implementation are briefly discussed. 1. What Does ab Initio Quantum Chemistry Try To Do? quantitative predictions to be made.
    [Show full text]
  • B3.1 Quantum Structural Methods for Atoms and Molecules
    Quantum structural methods for atoms and molecules 1907 B3.1 Quantum structural methods for atoms and molecules Jack Simons B3.1.1 What does quantum chemistry try to do? Electronic structure theory describes the motions of the electrons and produces energy surfaces and wave- functions. The shapes and geometries of molecules, their electronic, vibrational and rotational energy levels, as well as the interactions of these states with electromagnetic fields lie within the realm of quantum structure theory. B3.1.1.1 The underlying theoretical basis—the Born–Oppenheimer model In the Born–Oppenheimer [1] model, it is assumed that the electrons move so quickly that they can adjust their motions essentially instantaneously with respect to any movements of the heavier and slower atomic nuclei. In typical molecules, the valence electrons orbit about the nuclei about once every 10−15 s (the inner-shell electrons move even faster), while the bonds vibrate every 10−14 s, and the molecule rotates approximately every 10−12 s. So, for typical molecules, the fundamental assumption of the Born–Oppenheimer model is valid, but for loosely held (e.g. Rydberg) electrons and in cases where nuclear motion is strongly coupled to electronic motions (e.g. when Jahn–Teller effects are present) it is expected to break down. This separation-of-time-scales assumption allows the electrons to be described by electronic wavefunc- tions that smoothly ‘ride’ the molecule’s atomic framework. These electronic functions are found by solving ˆ a Schrodinger¨ equation whose Hamiltonian He contains the kinetic energy Te of the electrons, the Coulomb repulsions among all the molecule’s electrons Vee, the Coulomb attractions Ven among the electrons and all of the molecule’s nuclei, treated with these nuclei held clamped, and the Coulomb repulsions Vnn among all of these nuclei, but it does not contain the kinetic energy TN of all the nuclei.
    [Show full text]
  • Bsc Chemistry
    ____________________________________________________________________________________________________ Subject Chemistry Paper No and Title 2 and Physical Chemistry-I Module No and Title 27 and Valence Bond Theory I Module Tag CHE_P2_M27 SUBJECT PAPER : 2, Physical Chemistry I MODULE : 27, Valence Bond Theory I ____________________________________________________________________________________________________ TABLE OF CONTENTS 1. Learning Outcomes 2. Introduction 3. Valence Bond Theory (VBT) 3.1 Postulates of VBT 3.2 VBT of Hydrogen molecule 4. Summary 1. SUBJECT PAPER : 2, Physical Chemistry I MODULE : 27, Valence Bond Theory I ____________________________________________________________________________________________________ 1. Learning Outcomes After studying this module, you shall be able to: Learn about electronic structure of molecules using VBT Understand the postulates of VBT The VBT of Hydrogen molecule 2. Introduction Now, at this point we know that the Schrodinger equation cannot be solved exactly for multi-electron system even if the inter-nuclear distances are held constant. This is due to the presence of electron-electron repulsion terms in the Hamiltonian operator. Consequently, various approaches have been developed for the approximate solution of Schrodinger equation. Of these, Molecular Orbital Theory (MOT) and Valence Bond Theory (VBT) have been widely used. These two approaches differ in the choice of trial/approximate wave-function which is optimized via variation method for the system under consideration. Of these, we have already discussed MOT in earlier modules. In this module, we will take up the formalism of VBT in detail. 3. Valence Bond Theory Valence Bond Theory was the first quantum mechanical treatment to account for chemical bonding. This theory was first introduced by Heitler and London in 1927 and subsequently by Slater and Pauling in 1930s.
    [Show full text]
  • Valence Bond Theory
    Valence Bond Theory • A bond is a result of overlapping atomic orbitals from two atoms. The overlap holds a pair of electrons. • Normally each atomic orbital is bringing one electron to this bond. But in a “coordinate covalent bond”, both electrons come from the same atom • In this model, we are not creating a new orbital by the overlap. We are simply referring to the overlap between atomic orbitals (which may or may not be hybrid) from two atoms as a “bond”. Valence Bond Theory Sigma (σ) Bond • Skeletal bonds are called “sigma” bonds. • Sigma bonds are formed by orbitals approaching and overlapping each other head-on . Two hybrid orbitals, or a hybrid orbital and an s-orbital, or two s- orbitals • The resulting bond is like an elongated egg, and has cylindrical symmetry. Acts like an axle • That means the bond shows no resistance to rotation around a line that lies along its length. Pi (π) Bond Valence Bond Theory • The “leftover” p-orbitals that are not used in forming hybrid orbitals are used in making the “extra” bonds we saw in Lewis structures. The 2 nd bond in a double bond nd rd The 2 and 3 bonds in a triple bond /~harding/IGOC/P/pi_bond.html • Those extra bonds form only after the atoms are brought together by the formation of the skeletal bonds made by www.chem.ucla.edu hybrid orbitals. • The “extra” π bonds are always associated with a skeletal bond around which they form. • They don’t form without a skeletal bond to bring the p- orbitals together and “support” them.
    [Show full text]
  • Visualizing Molecules - VSEPR, Valence Bond Theory, and Molecular Orbital Theory
    Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Visualizing Molecules - VSEPR, Valence Bond Theory, and Molecular Orbital Theory Nestor S. Valera 1 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Visualizing Molecules 1. Lewis Structures and Valence-Shell Electron-Pair Repulsion Theory 2. Valence Bond Theory and Hybridization 3. Molecular Orbital Theory 2 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Shapes of Molecules 10.1 Depicting Molecules and Ions with Lewis Structures 10.2 Valence-Shell Electron-Pair Repulsion (VSEPR) Theory and Molecular Shape 10.3 Molecular Shape and Molecular Polarity 3 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 10.1 The steps in converting a molecular formula into a Lewis structure. Place atom Molecular Step 1 with lowest formula EN in center Atom Add A-group Step 2 placement numbers Sum of Draw single bonds. Step 3 valence e- Subtract 2e- for each bond. Give each Remaining Step 4 atom 8e- valence e- (2e- for H) Lewis structure 4 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Molecular formula For NF3 Atom placement : : N 5e- : F: : F: : Sum of N F 7e- X 3 = 21e- valence e- - : F: Total 26e Remaining : valence e- Lewis structure 5 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. SAMPLE PROBLEM 10.1 Writing Lewis Structures for Molecules with One Central Atom PROBLEM: Write a Lewis structure for CCl2F2, one of the compounds responsible for the depletion of stratospheric ozone.
    [Show full text]
  • New Conceptual Understanding of Lewis Acidity, Coordinate Covalent Bonding, and Catalysis Joshua A
    Duquesne University Duquesne Scholarship Collection Electronic Theses and Dissertations Summer 2009 New Conceptual Understanding of Lewis Acidity, Coordinate Covalent Bonding, and Catalysis Joshua A. Plumley Follow this and additional works at: https://dsc.duq.edu/etd Recommended Citation Plumley, J. (2009). New Conceptual Understanding of Lewis Acidity, Coordinate Covalent Bonding, and Catalysis (Doctoral dissertation, Duquesne University). Retrieved from https://dsc.duq.edu/etd/1052 This Immediate Access is brought to you for free and open access by Duquesne Scholarship Collection. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of Duquesne Scholarship Collection. For more information, please contact [email protected]. NEW CONCEPTUAL UNDERSTANDING OF LEWIS ACIDITY, COORDINATE COVALENT BONDING, AND CATALYSIS A Dissertation Submitted to the Bayer School of Natural and Environmental Sciences Duquesne University In partial fulfillment of the requirements for the degree of Doctor of Philosophy By Joshua A. Plumley August 2009 NEW CONCEPTUAL UNDERSTANDING OF LEWIS ACIDITY, COORDINATE COVALENT BONDING, AND CATALYSIS By Joshua A. Plumley Approved August 2009 __________________________________ __________________________________ Jeffrey D. Evanseck Ellen Gawalt Professor of Chemistry and Biochemistry Assistant Professor of Chemistry and Dissertation Director Biochemistry Committee Member Committee Member __________________________________ __________________________________ Douglas J. Fox
    [Show full text]
  • "The Atom and the Molecule " Di Gilbert N. Lewis Articolo Originale
    "The Atom and the Molecule " di Gilbert N. Lewis articolo originale Scritto da Roberto Poeti Domenica 20 Settembre 2009 22:43 - Ultimo aggiornamento Mercoledì 07 Ottobre 2009 20:40 The Atom and the Molecule by Gilbert N. Lewis Journal of the American Chemical Society Volume 38, 1916, pages 762-786 Received January 26, 1916 762 In a paper entitled "Valence and Tautomerism"1 I took occasion 1 This Journal, 35, 1448 (1913); see also the important article of Bray and Branch, Ibid, 35, 1440 (1913) 763 to point out the great importance of substituting for the conventional classification of chemical substances, as inorganic or organic, the more general classification which distinguishes between polar and nonpolar substances. The two classifications roughly coincide, since most inorganic substances are distinctly polar, while the majority of organic substances belong to the nonpolar class; thus potassium chloride represents the extreme polar type and methane the nonpolar. Nevertheless, there are many inorganic substances which, under ordinary circumstances, are predominantly nonpolar, and many organic substances which, at least in a certain part of the molecule, are strongly polar. This article was apparently unknown to Sir J.J. Thomson1 when he wrote, in 1914, an extremely interesting paper on the "Forces between Atoms and Chemical Affinity" in which he reached conclusions in striking accord with my own and discussed in considerable detail the theories of 1 / 21 "The Atom and the Molecule " di Gilbert N. Lewis articolo originale Scritto da Roberto Poeti Domenica 20 Settembre 2009 22:43 - Ultimo aggiornamento Mercoledì 07 Ottobre 2009 20:40 atomic and molecular structure which led him to those conclusions.
    [Show full text]
  • Acronyms Used in Theoretical Chemistry
    Pure & Appl. Chem., Vol. 68, No. 2, pp. 387-456, 1996. Printed in Great Britain. INTERNATIONAL UNION OF PURE AND APPLIED CHEMISTRY PHYSICAL CHEMISTRY DIVISION WORKING PARTY ON THEORETICAL AND COMPUTATIONAL CHEMISTRY ACRONYMS USED IN THEORETICAL CHEMISTRY Prepared for publication by the Working Party consisting of R. D. BROWN* (Australia, Chiman);J. E. BOWS (USA); R. HILDERBRANDT (USA); K. LIM (Australia); I. M. MILLS (UK); E. NIKITIN (Russia); M. H. PALMER (UK). The focal point to which to send comments and suggestions is the coordinator of the project: RONALD D. BROWN Chemistry Department, Monash University, Clayton, Victoria 3 168, Australia. Responses by e-mail would be particularly appreciated, the number being: rdbrown @ vaxc.cc .monash.edu.au another alternative is fax at: +61 3 9905 4597 Acronyms used in theoretical chemistry synogsis An alphabetic list of acronyms used in theoretical chemistry is presented. Some explanatory references have been added to make acronyms better understandable but still more are needed. Critical comments, additional references, etc. are requested. INTRODUC'IION The IUPAC Working Party on Theoretical Chemistry was persuaded, by discussion with colleagues, that the compilation of a list of acronyms used in theoretical chemistry would be a useful contribution. Initial lists of acronyms drawn up by several members of the working party have been augmented by the provision of a substantial list by Chemical Abstract Service (see footnote below). The working party is particularly grateful to CAS for this generous help. It soon became apparent that many of the acron ms needed more than mere spelling out to make them understandable and so we have added expr anatory references to many of them.
    [Show full text]
  • 1997) 150–163
    Eur. J. Phys. 18 (1997) 150–163. Printed in the UK PII: S0143-0807(97)80684-8 The chemists’ electron Theodore Arabatzis and Kostas Gavroglu Department of History and Philosophy of Science, University of Athens, Greece Received 6 January 1997, in final form 13 February 1997 Abstract. This paper narrates the way chemists have been Resum´ e.´ Dans cet article on narre comment l’electron´ avait using the electron to account for one of the most intriguing et´ e´ utilise´ par les chimistes, afin de rendre compte d’un problems, namely the bonding of two neutral atoms to form a probleme` intriguant, notamment celui de la liaison de deux molecule. The chemists’ attempts to account for the atomes neutres pour former une molecule.´ Les efforts des mechanism of the homopolar bond, first in the context of the chimistes de rendre compte du mecanisme´ de la liaison old quantum theory and after 1926 in the context of wave homopolaire, d’abord dans le contexte de la theorie´ quantique mechanics, brought the specter of reductionism to physics. ancienne, ensuite, apres´ 1926, dans le contexte de la We argue that the chemists’ successful appropriation of the mecanique´ ondulatoire, a fait entrer dans la Physique le electron strengthened, first, the autonomy of physical spectre du reductionnisme.´ Nous soutenons la these` que chemistry and, then, of quantum chemistry with respect to l’appropriation reussie´ de l’electron´ par les chimistes a physics. renforcee´ l’autonomie, par rapport a` la Physique, d’abord de la chimie physique et, ensuite, de la chimie quantique. 1. Introduction which was so appealing to the chemists, obliged the chemists to re-acquisition what they felt was theirs in The aim of Robert Millikan’s Faraday lecture before the first place.
    [Show full text]