DOCSLIB.ORG

Bond Lengths and Bond Valences of Ions Bonded to Oxygen

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Bond Lengths and Bond Valences of Ions Bonded to Oxygen BOND LENGTHS AND BOND VALENCES OF IONS BONDED TO OXYGEN: THEIR VARIABILITY IN INORGANIC CRYSTALS by Olivier Gagné A Thesis submitted to the Faculty of Graduate Studies of The University of Manitoba in partial fulfilment of the requirements of the degree of DOCTOR OF PHILOSOPHY Department of Geological Sciences University of Manitoba Winnipeg Copyright © 2016 by Olivier Gagné ABSTRACT A large amount of information concerning interatomic distances in the solid state is available, but little has been done in recent times to comprehensively filter, summarize and analyze this information. Here, I examine the distribution of bond lengths for 135 ions bonded to oxygen, using 180,331 bond lengths extracted from 9367 refined crystal structures collected from the Inorganic Crystal Structure Database (ICSD). The data are used to evaluate the parameterization of the bond-length—bond-valence relation of the bond-valence model. Published bond-valence parameters for 135 cations bonded to oxygen, and the various methods used in their derivation, are evaluated. New equations to model the relation are tested and the common form of the equation is found to be satisfactory. A new method (the Generalized Reduced Gradient Method, GRG method) is used to derive new bond-valence parameters for 135 cations bonded to oxygen, leading to significant improvements in fit for many of the ions. The improved parameterization is used to gain crystal-chemical insight into the milarite structure. A literature review of 350+ published compositions is done to review the end- members of the milarite group and to identify compositions that should have been described as distinct minerals species. The a priori bond-valences are calculated for minerals of this structure, and are used to examine the controls of bond topology on site occupancy, notably by localizing the major source of strain of the structure (the B site). Examination of the compositions of all known milarite-group minerals shows that compositions with a fully occupied B site are less common than those with a vacant B site, in accord with the idea that the B site is a local region of high strain in the structure. ii The bond-length distributions for the ions of the alkali and alkaline-earth metal families are examined. Variations in mean bond-lengths are only partly explained by the distortion theorem of the bond-valence model. I have found that bond length also correlates with the amount of vibrational displacement of the constituent ions. The validity of some uncommon coordination numbers, e.g., [3]-coordinated Li+, [3]- coordinated Be2+, is confirmed. iii ACKNOWLEDGEMENTS First and foremost, I thank my thesis advisor Frank. C. Hawthorne for his help, support, encouragement and dedication over the course of my degree, and for providing me with an environment in which I was able to flourish. I thank members of my Ph.D. thesis committee, Elena Sokolova, Norman Halden, Scott Kroeker and Peter Budzelaar for their support, positivity, and helpful commentary, and the support staff of the department of Geological Sciences at the University of Manitoba. I thank the Natural Sciences and Engineering Research Council (NSERC) for a PGS-D3 scholarship, the University of Manitoba’s Faculty of Graduate Studies for a Duff Roblin and GETS Fellowships, the Mineralogical Association of Canada for awarding me with a MAC Foundation scholarship, the C.H.R. Faculty of Environment, Earth and Resources for an Entrance and Graduate Student Initiative Scholarships, and the Department of Geological Sciences for Rita Wadien scholarships. I thank Patrick Mercier and Yvon Lepage of the National Research Council for providing help in shaping research themes early on in the project, and Éric Martineault and Yulia Uvarova whom I could always count on for advice and entertaining discussions. Last but not least, I thank my family members, who were always present and supportive of my (often questionable) decisions. Merci Maman, Mathieu et Amélie. Finally, I thank my friends, especially the ones that tend to jump out of airplanes and things, whom I could always count on to clear my mind in time of need. Shout out to my 4-way skydiving team, team Alphaghetti. iv “This is for the kids who have nowhere to turn Who have nothing to live for You think you haven't the will to persist You have to search within yourself” -Jamey Jasta v TABLE OF CONTENTS Abstract.............................................................................................................................ii Acknowledgements..........................................................................................................iv Dedication.........................................................................................................................v List of Tables..................................................................................................................xvi List of Figures.................................................................................................................xix Contributions of Authors...............................................................................................xxiv List of Copyrighted Material for which Permission was Obtained................................xxvii Chapter 1. Introduction..................................................................................................1 1.1 General introduction……………………………………………………...……..….2 1.1.1 Concepts of crystal chemistry............................................................3 1.1.1.1 The internal structure of crystals..........................................4 1.1.1.2 Interatomic distances and ionic radii....................................8 1.1.1.3 The chemical bond and chemical bonding...........................9 1.1.2 Interatomic distances in the solid state............................................11 1.1.2.1 Bond lengths for cations bonded to O2-..............................12 1.1.3 The types of chemical bonds...........................................................13 vi 1.1.3.1 Ionic bonding……………………………………………..……14 1.1.3.2 Covalent bonding…………………………........................…17 1.1.3.3 Metallic bonding………………………………........…………19 1.1.3.4 Van der Waals bonding…………………….........................19 1.1.3.5 Hydrogen bonding…………...............………………………20 1.1.4 Theories of chemical bonding..........................................................20 1.1.4.1 Valence-bond theory..........................................................21 1.1.4.2 Molecular orbital (MO) theory.............................................21 1.1.4.3 Bond-valence theory..........................................................22 1.1.4.3.1 Theoretical basis of bond-valence theory.............23 1.1.4.3.2 The bond-valence model......................................27 1.2 Objectives and Significance of Research......................................................29 1.3 Structure of the thesis…………………............................................…...…….31 1.4 References……………………................................................................…….33 Chapter 2. Comprehensive derivation of bond-valence parameters for ion pairs involving oxygen……...................................................................................................41 2.1 Synopsis........................................................................................................42 2.2 Abstract..........................................................................................................42 2.3 Introduction....................................................................................................43 vii 2.4 Experimental bond-lengths used in this work................................................45 2.5 Method of evaluation of bond-valence parameters........................................46 2.6 Evaluation of published oxide bond-valence parameters..............................47 2.7 The hydrogen atom........................................................................................49 2.8 Use of bond-valence parameters for hydrogen-oxygen bonds......................50 2.9 Comments on fixing the B parameter............................................................51 2.10 Comments on the level of fit........................................................................52 2.11 Parameterization..........................................................................................53 2.11.1 Methods of derivation of the bond-valence parameters.................53 2.11.1.1 Least-squares fitting.........................................................53 2.11.1.2 Fixing the B parameter.....................................................54 2.11.1.3 Graphical method: cation and anion sums.......................55 2.11.1.2 Graphical method: cation sums........................................56 2.11.1.5 RMSD minimization..........................................................58 2.11.2 Generalized Reduced Gradient (GRG) method of RMSD minimization...................................................................................59 2.11.2.1 The Generalized Reduced Gradient method....................60 2.11.2.2 Weighting scheme............................................................63 2.11.3 Comparison of the most common methods of derivation...............63 viii 2.11.4 General considerations..................................................................70 2.11.4.1 Optimizing both cation and anion bond-valence sums.....70 2.11.4.2 On the universality of the bond-valence
Load more

Recommended publications
  • The Dependence of the Sio Bond Length on Structural Parameters in Coesite, the Silica Polymorphs, and the Clathrasils
    American Mineralogist, Volume 75, pages 748-754, 1990 The dependence of the SiO bond length on structural parameters in coesite, the silica polymorphs, and the clathrasils M. B. BOISEN, JR. Department of Mathematics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, U.S.A. G. V. GIBBS, R. T. DOWNS Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, U.S.A. PHILIPPE D' ARCO Laboratoire de Geologie, Ecole Normale Superieure, 75230 Paris Cedex OS, France ABSTRACT Stepwise multiple regression analyses of the apparent R(SiO) bond lengths were com- pleted for coesite and for the silica polymorphs together with the clathrasils as a function of the variables};(O), P (pressure), f,(Si), B(O), and B(Si). The analysis of 94 bond-length data recorded for coesite at a variety of pressures and temperatures indicates that all five of these variables make a significant contribution to the regression sum of squares with an R2 value of 0.84. A similar analysis of 245 R(SiO) data recorded for silica polymorphs and clathrasils indicate that only three of the variables (B(O), };(O), and P) make a signif- icant contribution to the regression with an R2 value of 0.90. The distribution of B(O) shows a wide range of values from 0.25 to 10.0 A2 with nearly 80% of the observations clustered between 0.25 and 3.0 A2 and the remaining values spread uniformly between 4.5 and 10.0 A2. A regression analysis carried out for these two populations separately indicates, for the data set with B(O) values less than three, that };(O) B(O), P, and };(Si) are all significant with an R2 value of 0.62.
    [Show full text]
  • The Nafure of Silicon-Oxygen Bonds
    AmericanMineralogist, Volume 65, pages 321-323, 1980 The nafure of silicon-oxygenbonds LtNus PeurrNc Linus Pauling Institute of Scienceand Medicine 2700 Sand Hill Road, Menlo Park, California 94025 Abstract Donnay and Donnay (1978)have statedthat an electron-densitydetermination carried out on low-quartz by R. F. Stewart(personal communication), which assignscharges -0.5 to the oxygen atoms and +1.0 to the silicon atoms, showsthe silicon-oxygenbond to be only 25 percentionic, and hencethat "the 50/50 descriptionofthe past fifty years,which was based on the electronegativity difference between Si and O, is incorrect." This conclusion, however, ignoresthe evidencethat each silicon-oxygenbond has about 55 percentdouble-bond char- acter,the covalenceof silicon being 6.2,with transferof 2.2 valenc,eelectrons from oxygen to silicon. Stewart'svalue of charge*1.0 on silicon then leads to 52 percentionic characterof the bonds, in excellentagreement with the value 5l percent given by the electronegativity scale. Donnay and Donnay (1978)have recently referred each of the four surrounding oxygen atoms,this ob- to an "absolute" electron-densitydetermination car- servationleads to the conclusionthat the amount of ried out on low-quartz by R. F. Stewart, and have ionic character in the silicon-oxygsa 5ingle bond is statedthat "[t showsthe Si-O bond to be 75 percent 25 percent. It is, however,not justified to make this covalent and only 25 percent ionic; the 50/50 de- assumption. scription of the past fifty years,which was basedon In the first edition of my book (1939)I pointed out the electronegativitydifference between Si and O, is that the observedSi-O bond length in silicates,given incorrect." as 1.604, is about 0.20A less than the sum of the I formulated the electronegativityscale in 1932, single-bond radii of the two atoms (p.
    [Show full text]
  • Atomic Structures of the M Olecular Components in DNA and RNA Based on Bond Lengths As Sums of Atomic Radii
    1 Atomic St ructures of the M olecular Components in DNA and RNA based on Bond L engths as Sums of Atomic Radii Raji Heyrovská (Institute of Biophysics, Academy of Sciences of the Czech Republic) E-mail: [email protected] Abstract The author’s interpretation in recent years of bond lengths as sums of the relevant atomic/ionic radii has been extended here to the bonds in the skeletal structures of adenine, guanine, thymine, cytosine, uracil, ribose, deoxyribose and phosphoric acid. On examining the bond length data in the literature, it has been found that the averages of the bond lengths are close to the sums of the corresponding atomic covalent radii of carbon (tetravalent), nitrogen (trivalent), oxygen (divalent), hydrogen (monovalent) and phosphorus (pentavalent). Thus, the conventional molecular structures have been resolved here (for the first time) into probable atomic structures. 1. Introduction The interpretation of the bond lengths in the molecules constituting DNA and RNA have been of interest ever since the discovery [1] of the molecular structure of nucleic acids. This work was motivated by the earlier findings [2a,b] that the inter-atomic distance between any two atoms or ions is, in general, the sum of the radii of the atoms (and or ions) constituting the chemical bond, whether the bond is partially or fully ionic or covalent. It 2 was shown in [3] that the lengths of the hydrogen bonds in the Watson- Crick [1] base pairs (A, T and C, G) of nucleic acids as well as in many other inorganic and biochemical compounds are sums of the ionic or covalent radii of the hydrogen donor and acceptor atoms or ions and of the transient proton involved in the hydrogen bonding.
    [Show full text]
  • Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc
    Metal-Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc Richard H. Duncan Lyngdoh*,a, Henry F. Schaefer III*,b and R. Bruce King*,b a Department of Chemistry, North-Eastern Hill University, Shillong 793022, India B Centre for Computational Quantum Chemistry, University of Georgia, Athens GA 30602 ABSTRACT: This survey of metal-metal (MM) bond distances in binuclear complexes of the first row 3d-block elements reviews experimental and computational research on a wide range of such systems. The metals surveyed are titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc, representing the only comprehensive presentation of such results to date. Factors impacting MM bond lengths that are discussed here include (a) n+ the formal MM bond order, (b) size of the metal ion present in the bimetallic core (M2) , (c) the metal oxidation state, (d) effects of ligand basicity, coordination mode and number, and (e) steric effects of bulky ligands. Correlations between experimental and computational findings are examined wherever possible, often yielding good agreement for MM bond lengths. The formal bond order provides a key basis for assessing experimental and computationally derived MM bond lengths. The effects of change in the metal upon MM bond length ranges in binuclear complexes suggest trends for single, double, triple, and quadruple MM bonds which are related to the available information on metal atomic radii. It emerges that while specific factors for a limited range of complexes are found to have their expected impact in many cases, the assessment of the net effect of these factors is challenging.
    [Show full text]
  • Bond-Length Distributions for Ions Bonded to Oxygen: Results for the Lanthanides and Actinides and Discussion of the F-Block Contraction
    To appear in Acta Crystallographica Section B Bond-length distributions for ions bonded to oxygen: Results for the lanthanides and actinides and discussion of the f-block contraction Olivier Charles Gagnéa* aGeological Sciences, University of Manitoba, 125 Dysart Road, Winnipeg, Manitoba, R3T 2N2, Canada Correspondence email: [email protected] Synopsis Bond-length distributions have been examined for eighty-four configurations of the lanthanide ions and twenty-two configurations of the actinide ions bonded to oxygen. The lanthanide contraction for the trivalent lanthanide ions bonded to O2- is shown to vary as a function of coordination number and to diminish in scale with increasing coordination number. Abstract Bond-length distributions have been examined for eighty-four configurations of the lanthanide ions and twenty-two configurations of the actinide ions bonded to oxygen, for 1317 coordination polyhedra and 10,700 bond distances for the lanthanide ions, and 671 coordination polyhedra and 4754 bond distances for the actinide ions. A linear correlation between mean bond-length and coordination number is observed for the trivalent lanthanides ions bonded to O2-. The lanthanide contraction for the trivalent lanthanide ions bonded to O2- is shown to vary as a function of coordination number, and to diminish in scale with an increasing coordination number. The decrease in mean bond- length from La3+ to Lu3+ is 0.25 Å for CN 6 (9.8%), 0.22 Å for CN 7 (8.7%), 0.21 Å for CN 8 (8.0%), 0.21 Å for CN 9 (8.2%) and 0.18 Å for CN 10 (6.9%). The crystal chemistry of Np5+ and Np6+ is shown to be very similar to that of U6+ when bonded to O2-, but differs for Np7+.
    [Show full text]
  • Chapter 5 the Covalent Bond 1
    Chapter 5 The Covalent Bond 1. What two opposing forces dictate the bond length? (Why do bonds form and what keeps the bonds from getting any shorter?) The bond length is the distance at which the repulsion of the two nuclei equals the attraction of the valence electrons on one atom and the nucleus of the other. 3. List the following bonds in order of increasing bond length: H-Cl, H-Br, H-O. H-O < H-Cl < H-Br. The order of increasing atom size. 5. Use electronegativities to describe the nature (purely covalent, mostly covalent, polar covalent, or ionic) of the following bonds. a) P-Cl Δχ = 3.0 – 2.1 = 0.9 polar covalent b) K-O Δχ = 3.5 – 0.8 = 2.7 ionic c) N-H Δχ = 3.0 – 2.1 = 0.9 polar covalent d) Tl-Br Δχ = 2.8 – 1.7 = 1.1 polar covalent 7. Name the following compounds: a) S2Cl2 disulfur dichloride b) CCl4 carbon tetrachloride c) PCl5 phosphorus pentachloride d) HCl hydrogen chloride 9. Write formulas for each of the following compounds: a) dinitrogen tetroxide N2O4 b) nitrogen monoxide NO c) dinitrogen pentoxide N2O5 11. Consider the U-V, W-X, and Y-Z bonds. The valence orbital diagrams for the orbitals involved in the bonds are shown in the margin. Use an arrow to show the direction of the bond dipole in the polar bonds or indicate “not polar” for the nonpolar bond(s). Rank the bonds in order of increasing polarity. The bond dipole points toward the more electronegative atom in the bond, which is the atom with the lower energy orbital.
    [Show full text]
  • CH 101Fall 2018 Discussion #13 Chapter 10 Your Name: TF's Name: D
    CH 101Fall 2018 Discussion #13 Chapter 10 Your name: _____________________________ TF’s name:______________________________ Discussion Day/Time: _______________ Things you should know when you leave Discussion today Atomic orbitals (s, p, d, f) vs. molecular orbitals (σ, σ*, NB, π, π*, πnb) Total Number of MO =Total Number of AO Constructive and destructive interference (in phase and out- of-phase interaction) o Sigma bond is achieved by head–on–overlap o Bonding MO (σ, π) - Constructive interference in-phase interaction o Antibonding MO (σ*, π*) - Destructive interference out-of-phase interaction o π formed from side-by-side overlap of available p AO . π* is out-of-phase overlap of available p AO . π is in-phase side-by-side overlap of available p AO Factors that affect the formation of MOs from AOs: S.O.E. o Symmetry AOs must have a compatible orientation to achieve an overlap. o Overlap: valence orbitals of correct symmetry. o Energy: If the pair of AO's has the correct symmetry and greatest overlap, and closest in energy 1 1. If you have two atoms that together have 5 atomic orbitals, when those atoms combine to form a molecule, how many molecular orbitals are you going to have? 2. For each of the AO combinations below, draw the resulting MO. What do we call that resulting MO? a. Discuss any axes of symmetry the MO may have. b. Is this MO destructive or constructive interference (or neither or both)? c. (at home) Draw as many other combinations of AOs that give σ and σ* MOs as you can, using only s and p AOs.
    [Show full text]
  • The Electronic Structure of Molecules an Experiment Using Molecular Orbital Theory
    The Electronic Structure of Molecules An Experiment Using Molecular Orbital Theory Adapted from S.F. Sontum, S. Walstrum, and K. Jewett Reading: Olmstead and Williams Sections 10.4-10.5 Purpose: Obtain molecular orbital results for total electronic energies, dipole moments, and bond orders for HCl, H 2, NaH, O2, NO, and O 3. The computationally derived bond orders are correlated with the qualitative molecular orbital diagram and the bond order obtained using the NO bond force constant. Introduction to Spartan/Q-Chem The molecule, above, is an anti-HIV protease inhibitor that was developed at Abbot Laboratories, Inc. Modeling of molecular structures has been instrumental in the design of new drug molecules like these inhibitors. The molecular model kits you used last week are very useful for visualizing chemical structures, but they do not give the quantitative information needed to design and build new molecules. Q-Chem is another "modeling kit" that we use to augment our information about molecules, visualize the molecules, and give us quantitative information about the structure of molecules. Q-Chem calculates the molecular orbitals and energies for molecules. If the calculation is set to "Equilibrium Geometry," Q-Chem will also vary the bond lengths and angles to find the lowest possible energy for your molecule. Q- Chem is a text-only program. A “front-end” program is necessary to set-up the input files for Q-Chem and to visualize the results. We will use the Spartan program as a graphical “front-end” for Q-Chem. In other words Spartan doesn’t do the calculations, but rather acts as a go-between you and the computational package.
    [Show full text]
  • Bond Length and Radii Variations in Fluoride and Oxide Molecules and Crystals
    Phys Chern Minerals (1994) 20:617-624 PHYSICS I!'mOOCHIMISTRY (lli MIIIRAlS «J Springer-Verlag 1994 Bond Length and Radii Variations in Fluoride and Oxide Molecules and Crystals J.S. Nicoll, G.V. Gibbs, M.B. Boisen, Jr., R.T. Downs, and K.L. Bartelmehs Department of Geological Sciences, Materials Science and Engineering and Mathematics, Virginia Tech, Blacksburg, VA 24061, USA Received June 8, 1993 / Revised, accepted September 24, 1993 Abstract. Molecular orbital calculations completed on Introduction fluoride molecules containing first and second row ca- tions have generated bond lengths, R, that match those In 1982, Gibbs suggested that a molecule might serve observed for coordinated polyhedra in crystals to within as a useful basis for modeling the bond length and angle ",0.04 A, on average. The calculated bond lengths and variations of a silicate mineral. This suggestion was those observed for fluoride crystals can be ranked with based on the observation that the separations and angles the expression R = Kp - 0.22, where p = sir, s is the Pauling between the Si and 0 atoms in the coordinated polyhe- strength of the bond, r is the row number of the cation dra of a number of siloxane molecules are not unlike and K = 1.34. The exponent - 0.22 (~ - 2/9) is the same those in quartz (Gibbs et al. 1972; Tossell and Gibbs as that observed for oxide, nitride and sulfide molecules 1978; Newton and Gibbs 1980; Gibbs et al. 1981; Gibbs and crystals. Bonded radii for the fluoride anion, ob- and Boisen 1986; Gibbs et al.
    [Show full text]
  • Atomic Structures of Graphene, Benzene and Methane with Bond Lengths As
    1 Atomic Structures of Graphene, Benzene and Methane with Bond Lengths as Sums of the Single, Double and Resonance Bond Radii of Carbon Raji Heyrovska Institute of Biophysics, Academy of Sciences of the Czech Republic. Email: [email protected] Abstract Two dimensional layers of graphene are currently drawing a great attention in fundamental and applied nanoscience. Graphene consists of interconnected hexagons of carbon atoms as in graphite. This article presents for the first time the structures of graphene at the atomic level and shows how it differs from that of benzene, due to the difference in the double bond and resonance bond based radii of carbon. The carbon atom of an aliphatic compound such as methane has a longer covalent single bond radius as in diamond. All the atomic structures presented here have been drawn to scale. Introduction A good introduction to graphene with diagrams and literature survey of the field can be found in [1,2]. It can be seen from [1] that research on graphene is currently pursued in many scientific institutions, and notably by the Geim group [2]. The structure of graphene is presently represented as a ball and stick model [3]. Since both benzene and graphene involve hexagonal arrangement of carbon atoms, a deeper insight into their atomic structures is provided here. Based on the author’s previous work on the atomic structures of moleclues with bond lengths as sums of atomic covalent radii [4-7], it is shown here that the bond lengths in the above molecules can also be represented as sums of the appropriate atomic radii of the carbon atoms involved.
    [Show full text]
  • Assessing Phosphine−Chalcogen Bond Energetics from Calculations Samuel R
    Chemistry Publications Chemistry 2015 Assessing Phosphine−Chalcogen Bond Energetics from Calculations Samuel R. Alvarado Iowa State University Ian A. Shortt Prairie View A & M University Hua-Jun Fan Prairie View A & M University Javier Vela Iowa State University Follow this and additional works at: http://lib.dr.iastate.edu/chem_pubs Part of the Inorganic Chemistry Commons The ompc lete bibliographic information for this item can be found at http://lib.dr.iastate.edu/ chem_pubs/106. For information on how to cite this item, please visit http://lib.dr.iastate.edu/ howtocite.html. This Article is brought to you for free and open access by the Chemistry at Iowa State University Digital Repository. It has been accepted for inclusion in Chemistry Publications by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Assessing Phosphine−Chalcogen Bond Energetics from Calculations Abstract Phosphine chalcogenides are useful reagents in chalcogen atom transfer reactions and nanocrystal syntheses. Understanding the strength and electronic structure of these bonds is key to optimizing their use, but a limited number of experimental and computational studies probe these issues. Using density functional theory (DFT), we computationally screen multiple series of trisubstituted phosphine chalcogenide molecules with a variety of phosphorus substituents and examine how these affect the strength of the phosphorus- chalcogen bond. DFT provides valuable data on these compounds including P-E bond dissociation energies, P-E bond order,Loẅ din charge on phosphorus and chalcogen atoms, and molecular geometries. Experimentally monitoring the 31P and 77Se NMR chemical shifts nda published Hammett onc stants provides good estimates and confirmation of the relative magnitude of electronic shielding around these nuclei and confirms the predictive value of the computational results.
    [Show full text]
  • Chapter 9 2010
    Announcements Chapter 9 Chapter 8 Chapter 9 (Read 279 to top 283) Skip mid-283- end of Section 9.2. Read Section 9.3 Skip 9.4 Read 9.5 Chapter 10 - 11.2 Read all of it Exam III (Chapter 7-11.2) Wednesday, September 29, 2010 Models of Chemical Bonding Time: 6:00PM - 7:30PM Rooms to be announced Chem 7 Comprehensive Final Exam Wednesday, Oct 13 1:30-3:30AM Chapter 1-11.2 + 12 60 multiple choice questions only Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Metal-Metal bonding or metallic bonding “pools Figure 9.2 The three models of chemical bonding. valence electrons” into an evenly distributed “sea” of delocalized electrons that can move freely (conduct electricity). 9- Atoms tend to form three types of chemical bonds: An ionic compound (salt) results from the chemical ionic, covalent and metallic. reaction between a metal and non-metal. Ionic Bonding: Electrons from one atom are Covalent compounds result from chemical reactions Covalent Bonding between non-metals. results from sharing transferred to another element (atom) that has a one or more electrons Cadmium pairs between atoms tendency to accept electrons (IE and EA). usually non-metals. Non-Metals transfer electrons share Metals electrons Bromine Iodine Valence electrons are the electrons in the outer Metals tend to loose (be oxidized) electrons while non- shell (highest value of n quantum number) of the metals tend to gain electrons (be reduced) to acquire atom that dictate chemistry & in chemical bonding. the noble gas configuration closest to them in the periodic table.
    [Show full text]