Covalent Bonding & Molecular Orbital Theory
|
|
- Amie Manning
- 7 years ago
- Views:
Transcription
1 Covalent Bonding & Molecular Orbital Theory Chemistry 754 Solid State Chemistry Dr. Patrick Woodward Lecture #16 References - MO Theory Molecular orbital theory is covered in many places including most general inorganic chemistry texts. The material for this lecture (along with many of the figures) was taken from the following two texts: Orbital Interactions in Chemistry Thomas Albright, Jeremy K. Burdett & Myung-Hwan Whangbo, Wiley & Sons, New York (1985). Chemical Bonding in Solids Jeremy K. Burdett, Oxford University Press, Oxford (1995).
2 Questions to Consider Why is H 2 O bent rather than linear? Why is NH 3 pyramidal rather than planar? Why are Sn and Pb metals, while Si and Ge are semiconductors? Why are the π electrons delocalized in benzene (C 6 H 6 ) and localized in cyclobutadiene (C 4 H 4 )? In oxides, chalcogenides and halides explain the following coordination preferences: Cu 2+ & Mn 3+ distorted octahedral environment Ni 2+ and Fe 3+ regular octahedral environment Pd 2+ and Pd 2+ square planar environment Pb 2+, Sn 2+, Bi 3+, Sb 3+ asymmetric coordination environment MO Diagram for H 2 The number of MO s is equal to the number of atomic orbitals. ach MO can hold 2 electrons (with opposite spins). The antibonding MO has a nodal plane between atoms and to the bond. As the spatial overlap increases ψ 1 (bonding MO) is stabilized and ψ 2 (antibonding MO) is destabilized. The destabilization of the antibonding MO is always greater than the stabilization of the bonding MO. In the diagrams at the top and bottom the solid line denotes the electron density from MO theory and the dashed line the electron density from superimposing to atomic orbitals.
3 1 st Order MO Diagram for O 2 The 2s orbitals have a lower energy than the 2p orbitals. The σ-bonds have a greater spatial overlap than the π-bonds. This leads to a larger splitting of the bonding and antibonding orbitals. The 2p x and 2p y π-interaction produces to two sets of degenerate orbitals. The MO s have symmetry descriptors, σ g+, σ u+, π g, π u within point group D h. Mixing is allowed between MO s s of the same symmetry. In O 2 there are 12 valence electrons and each of the 2pπ * orbitals (π g ) are singly occupied. Thus the bond order = 2, and O 2 is paramagnetic. 2 nd Order MO Diagram for O 2 (N 2 ) A more accurate depiction of the bonding takes into account mixing of of MO s with the same symmetry (σ + ( g & σ u+ ). The consequences of this 2 nd order effect are: The lower energy orbital is stabilized while the higher energy orbital is destablized. The s and p character of the σ MO s becomes mixed. The mixing becomes more pronounced as the energy separation decreases.
4 Heteronuclear Case & lectronegativity i The atomic orbitals of the more electronegative atom are lowered. The splitting between bonding and antibonding MO s now has an ionic (( i ) and a covalent (( c ) component. The ionic component of the splitting (( i ) increases as the electronegativity difference increases. The covalency and the covalent stabilization/destabilization decrease as the electronegativity difference increases. The orbital character of the more electronegative atom is enhanced in the bonding MO and diminished in the antibonding MO. Linear AX 2 (H 2 O) MO Diagram In linear H 2 O the O 2s and O 2p z orbitals could form σ-bonds to H, while the O 2p x & 2p y orbitals would be non-bonding.
5 Bent AX 2 (H 2 O) MO Diagram In bent H 2 O the O 2s σ orbital and the O 2p x orbital are allowed to mix by symmetry, lowering the energy of the O 2p x orbital. Now there is only one non-bonding orbital (O 2p y ) Walsh Diagrams & 2 nd Order JT Distortions HOMO Walsh Diagram Shows how the MO levels vary as a function of a geometrical change. Walsh s Rule A molecule adopts the structure that best stabilizes the HOMO. If the HOMO is unperturbed the occupied MO lying closest to it governs the geometrical preference. 2 nd Order Jahn-Teller Dist. A molecule with a small energy gap between the occupied and unoccupied MO s is susceptible to a structural distortion that allows intermixing between them.
6 Covalent Bonding & the Structure of Cristobalite Idealized β-cristobalite (SiO 2 ) Actual β-cristobalite (SiO 2 ) Space Group = Fd3m (Cubic) Si-O- -O-Si = 180 sp bonding at O 2-, 2 nonbonding O 2p orbitals Space Group = I-42d (Tetragonal) Si-O- -O-Si = 147 sp 2 bonding at O 2- Walsh Diagram for NH 3 HOMO In the planar (D 3h ) form the HOMO is a non-bonding O 2p orbital (a 2 ) containing 2 electrons. In the pyramidal (C 3v form the N 2s H 1s σ * orbital (a 1 ) can mix with the nonbonding O 2p orbital. Stabilizing the HOMO. 3v )
7 Tetrahedral AX 4 (CH 4 ) MO Diagram Notice that while both the 2s and 2p orbitals on Carbon are involved in bonding, in a perfect tetrahedron mixing of the s (a 1 ) and p (t 2 ) orbitals is forbidden. C 2p 2s Pb t * 2 a * 1 t 2 a 1 t * 2 Diamonds and Lead 2p 2s Structure & Properties of the Group 14 lements lement Structure g (ev) C Diamond 5.5 Si Diamond 1.1 Ge Diamond 0.7 α-sn Diamond 0.1 β-sn Tetragonal Metal Pb FCC Metal 6p 6s t 2 a 1 * a 1 6p 6s As you go proceed down the group the tendency for the s-orbitals to become involved in bonding diminishes. This destabilizes tetrahedral coordination and semiconducting/insulating behavior.
8 2 nd Order JT Distortion in PbO Pb 6s HOMO In both polymorphs of PbO (red PbO,, the tetragonal form is shown above) the Pb 2+ ions adopt a very asymmetric coordination environment. The driving force for this is to lower the energy of the filled, antibonding Pb 6s orbitals,, by mixing with an empty Pb 6p orbital. Such mixing is forbidden by symmetry in tetrahedral and octahedral coordination, so a distortion to a lower symmetry leading to the formation of the so-called stereoactive electron lone pair occurs. Such distortions are common for main group ions with their valence s electrons (Tl( +, Bi 3+, Sn 2+, Sb 3+, etc.). This distortion is similar to the one seen in NH 3. Benzene (C 6 H 6 ) Cyclic Polyenes Cyclobutadiene (C 4 H 4 ) Consider two cyclic C n H n systems. The sketches to the left show the phases of the C 2p z orbitals that are responsible for π-interactions. In each system there are n π-mo s. The lowest energy orbital has no nodes (all orbitals in phase) while the highest energy state has the maximum number (n/2). In C 6 H 6 there is a large HOMO- LUMO gap and the e 1g orbitals are fully occupied. In C 4 H 4 the e g orbital HOMO is ½ occupied (triplet ground state).
9 1 st Order Jahn-Teller Distortion in C 4 H 4 In practice cyclobutadiene does not form a regular square (D 4h ), but undergoes a distortion to a rectangular shape (D 2h ). This stabilizes one of the HOMO s (which becomes doubly occupied) and destabilizes the other (which becomes empty). This leads to formation of two localized double bonds. Hence, C 4 H 4 is said to be antiaromatic. 1 st Order Jahn-Teller Dist. A non-linear molecule with an incompletely filled degenerate HOMO is susceptible to a structural distortion that removes the degeneracy. Octahedral Coordination The diagram to the left shows a MO diagram for a transition metal octahedrally coordinated by σ-bonding ligands.. (π-bonding( has been neglected) Note that in an octahedron there is no mixing between s, p and d-orbitals orbitals. For a main group metal the same diagram applies, but we neglect the d- orbitals. The t 2g orbitals (d xy,d yz,d xz ) are π- antibonding (not shown), while the e g orbitals (d z2,d y2-y2 ) are σ- antibonding.. The latter are higher in energy since the spatial overlap of the σ-interaction is stronger.
10 Square Planar Coordination The diagram to the left shows a MO diagram for a transition metal in square planar coordination. (π-bonding( has been neglected) Among the changes the most important is that now the s and d z2 orbitals can mix, which stabilizes the d z2 and removes the degeneracy of the e g orbitals. Transition metals with electron counts that lead to partially filled e g orbitals (HS d 4, d 8 & d 9 in particular) will be prone to undergo distortions from octahedral toward square planar. The d 8 ions Pd 2+ and Pt 2+ have a strong preference for sq. planar coordination, but with Ni 2+ the crystal field splitting is usually too small to overcome the spin pairing energy and octahedral coordination results. Jahn-Teller Distortions: The long and the short of it. The Jahn-Teller theorem tells us there should be a distortion when the e g orbitals of a TM octahedral complex are partially occupied, but it doesn t tell us what type of distortion should occur. To a first approximation two choices give the same energetic stabilization. 2 long + 4 short bonds stabilizes the d z2 orbital 2 short + 4 long bonds stabilizes the d x2-y2 orbital.
11 Distortions in d 9 & d 10 Halides Short bonds drawn with solid lines. Long bonds drawn with dotted lines. In practice Cu 2+ (d 9 ) and Mn 3+ (HS) almost always take the 2 long + 4 short distortion,, and the distortions are usually considerably larger with Cu 2+. In contrast d 10 ions, such as Hg 2+ adopt very large 2 short + 4 long distortions (in many cases the distortion is so large that the coordination is essentially linear). For example consider the bond distances in CuBr 2 (4 2.40Å, Å) ) and HgBr 2 (4 3.23Å, Å), both of which adopt distorted CdI 2 structures. Why is this so? Why do d 10 ions distort at all? Jahn-Teller Distortions d z2 -s Mixing The empty ns s orbital is of appropriate symmetry to mix with the ( (n-1)d)d z2 orbital, but not with the ( (n-1)d)d x2-y2 orbital. This dictates the details of the dist. d 9 case (Cu 2+ ): The d z2 -s mixing favors preferential occupation of the d z2 orbital (2 long + 4 short favored) d 10 case (Hg 2+ ): The d z2 -s mixing is largest when the energy separation between the two is minimized ( ( 2 > 1 ). (2 short + 4 long favored)
Bonding Models. Bonding Models (Lewis) Bonding Models (Lewis) Resonance Structures. Section 2 (Chapter 3, M&T) Chemical Bonding
Bonding Models Section (Chapter, M&T) Chemical Bonding We will look at three models of bonding: Lewis model Valence Bond model M theory Bonding Models (Lewis) Bonding Models (Lewis) Lewis model of bonding
More informationChapter 9 - Covalent Bonding: Orbitals
Chapter 9 - Covalent Bonding: Orbitals 9.1 Hybridization and the Localized Electron Model A. Hybridization 1. The mixing of two or more atomic orbitals of similar energies on the same atom to produce new
More informationHybrid Molecular Orbitals
Hybrid Molecular Orbitals Last time you learned how to construct molecule orbital diagrams for simple molecules based on the symmetry of the atomic orbitals. Molecular orbitals extend over the entire molecule
More informationChemistry Workbook 2: Problems For Exam 2
Chem 1A Dr. White Updated /5/1 1 Chemistry Workbook 2: Problems For Exam 2 Section 2-1: Covalent Bonding 1. On a potential energy diagram, the most stable state has the highest/lowest potential energy.
More informationCHAPTER 5: MOLECULAR ORBITALS
Chapter 5 Molecular Orbitals 5 CHAPTER 5: MOLECULAR ORBITALS 5. There are three possible bonding interactions: p z d z p y d yz p x d xz 5. a. Li has a bond order of. (two electrons in a bonding orbital;
More informationChapter10 Tro. 4. Based on the Lewis structure, the number of electron domains in the valence shell of the CO molecule is A) 1 B) 2 C) 3 D) 4 E) 5
Chapter10 Tro 1. All of the geometries listed below are examples of the five basic geometries for molecules with more than 3 atoms except A) planar triangular B) octahedral C) tetrahedral D) trihedral
More informationChapter 10 Molecular Geometry and Chemical Bonding Theory
Chem 1: Chapter 10 Page 1 Chapter 10 Molecular Geometry and Chemical Bonding Theory I) VSEPR Model Valence-Shell Electron-Pair Repulsion Model A) Model predicts Predicts electron arrangement and molecular
More informationChapter 9. Chemical reactivity of molecules depends on the nature of the bonds between the atoms as well on its 3D structure
Chapter 9 Molecular Geometry & Bonding Theories I) Molecular Geometry (Shapes) Chemical reactivity of molecules depends on the nature of the bonds between the atoms as well on its 3D structure Molecular
More informationCovalent Bonding and Molecular Geometry
Name Section # Date of Experiment Covalent Bonding and Molecular Geometry When atoms combine to form molecules (this also includes complex ions) by forming covalent bonds, the relative positions of the
More informationch9 and 10 practice test
1. Which of the following covalent bonds is the most polar (highest percent ionic character)? A. Al I B. Si I C. Al Cl D. Si Cl E. Si P 2. What is the hybridization of the central atom in ClO 3? A. sp
More informationSHAPES OF MOLECULES (VSEPR MODEL)
1 SAPES MLEULES (VSEPR MDEL) Valence Shell Electron-Pair Repulsion model - Electron pairs surrounding atom spread out as to minimize repulsion. - Electron pairs can be bonding pairs (including multiple
More informationChapter 7. Comparing Ionic and Covalent Bonds. Ionic Bonds. Types of Bonds. Quick Review of Bond Types. Covalent Bonds
Comparing Ionic and Covalent Bonds Chapter 7 Covalent Bonds and Molecular Structure Intermolecular forces (much weaker than bonds) must be broken Ionic bonds must be broken 1 Ionic Bonds Covalent Bonds
More informationThe Lewis structure is a model that gives a description of where the atoms, charges, bonds, and lone pairs of electrons, may be found.
CEM110 Week 12 Notes (Chemical Bonding) Page 1 of 8 To help understand molecules (or radicals or ions), VSEPR shapes, and properties (such as polarity and bond length), we will draw the Lewis (or electron
More informationName: Class: Date: 3) The bond angles marked a, b, and c in the molecule below are about,, and, respectively.
Name: Class: Date: Unit 9 Practice Multiple Choice Identify the choice that best completes the statement or answers the question. 1) The basis of the VSEPR model of molecular bonding is. A) regions of
More informationChem 121 Problem Set V Lewis Structures, VSEPR and Polarity
hemistry 121 Problem set V olutions - 1 hem 121 Problem et V Lewis tructures, VEPR and Polarity AWER 1. pecies Elecronegativity difference in bond Bond Polarity Mp 3 E = 3.0-3.0 = 0 for - very weakly polar
More informationChapter 1 Structure and Bonding. Modified by Dr. Daniela Radu
John E. McMurry www.cengage.com/chemistry/mcmurry Chapter 1 Structure and Bonding Modified by Dr. Daniela Radu What is Organic Chemistry? Living things are made of organic chemicals Proteins that make
More information7.14 Linear triatomic: A-----B-----C. Bond angles = 180 degrees. Trigonal planar: Bond angles = 120 degrees. B < B A B = 120
APTER SEVEN Molecular Geometry 7.13 Molecular geometry may be defined as the three-dimensional arrangement of atoms in a molecule. The study of molecular geometry is important in that a molecule s geometry
More informationQuestion 4.2: Write Lewis dot symbols for atoms of the following elements: Mg, Na, B, O, N, Br.
Question 4.1: Explain the formation of a chemical bond. A chemical bond is defined as an attractive force that holds the constituents (atoms, ions etc.) together in a chemical species. Various theories
More informationVisualizing Molecular Orbitals: A MacSpartan Pro Experience
Introduction Name(s) Visualizing Molecular Orbitals: A MacSpartan Pro Experience In class we have discussed Lewis structures, resonance, VSEPR, hybridization and molecular orbitals. These concepts are
More informationCHEM 1211K Test IV. MULTIPLE CHOICE (3 points each)
CEM 1211K Test IV MULTIPLE COICE (3 points each) 1) ow many single covalent bonds must a silicon atom form to have a complete octet in its valence shell? A) 4 B) 3 C) 1 D) 2 E) 0 2) What is the maximum
More informationIonic Bonding Pauling s Rules and the Bond Valence Method
Ionic Bonding Pauling s Rules and the Bond Valence Method Chemistry 754 Solid State Chemistry Dr. Patrick Woodward Lecture #14 Pauling Rules for Ionic Structures Linus Pauling,, J. Amer. Chem. Soc. 51,,
More informationMolecular Orbital Theory
Molecular Orbital Theory To date, we have looked at three different theories of molecular boning. They are the VSEPR Theory (with Lewis Dot Structures), the Valence Bond Theory (with hybridization) and
More informationElements in the periodic table are indicated by SYMBOLS. To the left of the symbol we find the atomic mass (A) at the upper corner, and the atomic num
. ATOMIC STRUCTURE FUNDAMENTALS LEARNING OBJECTIVES To review the basics concepts of atomic structure that have direct relevance to the fundamental concepts of organic chemistry. This material is essential
More informationMolecular Geometry and VSEPR We gratefully acknowledge Portland Community College for the use of this experiment.
Molecular and VSEPR We gratefully acknowledge Portland ommunity ollege for the use of this experiment. Objectives To construct molecular models for covalently bonded atoms in molecules and polyatomic ions
More informationSection 3: Crystal Binding
Physics 97 Interatomic forces Section 3: rystal Binding Solids are stable structures, and therefore there exist interactions holding atoms in a crystal together. For example a crystal of sodium chloride
More informationEXPERIMENT 17 : Lewis Dot Structure / VSEPR Theory
EXPERIMENT 17 : Lewis Dot Structure / VSEPR Theory Materials: Molecular Model Kit INTRODUCTION Although it has recently become possible to image molecules and even atoms using a high-resolution microscope,
More informationLCAO-MO Correlation Diagrams
LCAO-MO Correlation Diagrams (Linear Combination of Atomic Orbitals to yield Molecular Orbitals) For (Second Row) Homonuclear Diatomic Molecules (X 2 ) - the following LCAO-MO s are generated: LCAO MO
More information: : Solutions to Additional Bonding Problems
Solutions to Additional Bonding Problems 1 1. For the following examples, the valence electron count is placed in parentheses after the empirical formula and only the resonance structures that satisfy
More informationAP Chemistry A. Allan Chapter 8 Notes - Bonding: General Concepts
AP Chemistry A. Allan Chapter 8 Notes - Bonding: General Concepts 8.1 Types of Chemical Bonds A. Ionic Bonding 1. Electrons are transferred 2. Metals react with nonmetals 3. Ions paired have lower energy
More information2. Atoms with very similar electronegativity values are expected to form
AP hemistry Practice Test #6 hapter 8 and 9 1. Which of the following statements is incorrect? a. Ionic bonding results from the transfer of electrons from one atom to another. b. Dipole moments result
More informationCHEM 340 CHEMICAL BONDING - in General Lect-07 IONIC COVALENT METAL COVALENT NETWORK
CHEM 340 CHEMICAL BONDING in General Lect07 BONDING between atoms classified as belonging to one of the following types: IONIC COVALENT METAL COVALENT NETWORK or each bond type, the valence shell electrons
More informationChemistry 111 Laboratory Experiment 4: Visualizing Molecular Orbitals with MacSpartan Pro (This experiment will be conducted in OR341)
Chemistry 111 Laboratory Experiment 4: Visualizing Molecular Orbitals with MacSpartan Pro (This experiment will be conducted in OR341) Introduction In class we have discussed Lewis structures, resonance,
More informationChemistry 105, Chapter 7 Exercises
hemistry 15, hapter 7 Exercises Types of Bonds 1. Using the periodic table classify the bonds in the following compounds as ionic or covalent. If covalent, classify the bond as polar or not. Mg2 4 i2 a(3)2
More informationTheme 3: Bonding and Molecular Structure. (Chapter 8)
Theme 3: Bonding and Molecular Structure. (Chapter 8) End of Chapter questions: 5, 7, 9, 12, 15, 18, 23, 27, 28, 32, 33, 39, 43, 46, 67, 77 Chemical reaction valence electrons of atoms rearranged (lost,
More informationMolecular-Orbital Theory
Molecular-Orbital Theory 1 Introduction Orbitals in molecules are not necessarily localized on atoms or between atoms as suggested in the valence bond theory. Molecular orbitals can also be formed the
More information5. Which of the following is the correct Lewis structure for SOCl 2
Unit C Practice Problems Chapter 8 1. Draw the lewis structures for the following molecules: a. BeF 2 b. SO 3 c. CNS 1- d. NO 2. The correct Lewis symbol for ground state carbon is a) b) c) d) e) 3. Which
More informationBonding & Molecular Shape Ron Robertson
Bonding & Molecular Shape Ron Robertson r2 n:\files\courses\1110-20\2010 possible slides for web\00bondingtrans.doc The Nature of Bonding Types 1. Ionic 2. Covalent 3. Metallic 4. Coordinate covalent Driving
More informationTRANSITION METALS AND COORDINATION CHEMISTRY
CHAPTER TWENTY-ONE TRANSITION METALS AND COORDINATION CHEMISTRY For Review 1. Chromium ([Ar]:4s 0 3d 5 ) and copper [Ar]:4s 1 3d 10 ) have electron configurations which are different from that predicted
More informationWe emphasize Lewis electron dot structures because of their usefulness in explaining structure of covalent molecules, especially organic molecules.
Chapter 10 Bonding: Lewis electron dot structures and more Bonding is the essence of chemistry! Not just physics! Chemical bonds are the forces that hold atoms together in molecules, in ionic compounds,
More informationUnit 3: Quantum Theory, Periodicity and Chemical Bonding
Selected Honour Chemistry Assignment Answers pg. 9 Unit 3: Quantum Theory, Periodicity and Chemical Bonding Chapter 7: The Electronic Structure of Atoms (pg. 240 to 241) 48. The shape of an s-orbital is
More informationEXPERIMENT 9 Dot Structures and Geometries of Molecules
EXPERIMENT 9 Dot Structures and Geometries of Molecules INTRODUCTION Lewis dot structures are our first tier in drawing molecules and representing bonds between the atoms. The method was first published
More informationCHEMISTRY BONDING REVIEW
Answer the following questions. CHEMISTRY BONDING REVIEW 1. What are the three kinds of bonds which can form between atoms? The three types of Bonds are Covalent, Ionic and Metallic. Name Date Block 2.
More informationRole of Hydrogen Bonding on Protein Secondary Structure Introduction
Role of Hydrogen Bonding on Protein Secondary Structure Introduction The function and chemical properties of proteins are determined by its three-dimensional structure. The final architecture of the protein
More information3) Of the following, radiation has the shortest wavelength. A) X-ray B) radio C) microwave D) ultraviolet E) infrared Answer: A
1) Which one of the following is correct? A) ν + λ = c B) ν λ = c C) ν = cλ D) λ = c ν E) νλ = c Answer: E 2) The wavelength of light emitted from a traffic light having a frequency of 5.75 1014 Hz is.
More informationBenzene and Aromatic Compounds
Benzene and Aromatic Compounds Benzene (C 6 H 6 ) is the simplest aromatic hydrocarbon (or arene). Benzene has four degrees of unsaturation, making it a highly unsaturated hydrocarbon. Whereas unsaturated
More informationVocabulary: VSEPR. 3 domains on central atom. 2 domains on central atom. 3 domains on central atom NOTE: Valence Shell Electron Pair Repulsion Theory
Vocabulary: VSEPR Valence Shell Electron Pair Repulsion Theory domain = any electron pair, or any double or triple bond is considered one domain. lone pair = non-bonding pair = unshared pair = any electron
More informationElectronegativity and Polarity MAIN Idea A chemical bond s character is related to each atom s
Section 8.5 Objectives Describe how electronegativity is used to determine bond type. Compare and contrast polar and nonpolar covalent bonds and polar and nonpolar molecules. Generalize about the characteristics
More informationChapter 8 Concepts of Chemical Bonding
Chapter 8 Concepts of Chemical Bonding Chemical Bonds Three types: Ionic Electrostatic attraction between ions Covalent Sharing of electrons Metallic Metal atoms bonded to several other atoms Ionic Bonding
More informationElectron Counting in Organometallic Chemistry
Electron Counting in Organometallic Chemistry 1. The 18-Electron Rule; definition & rationalisation The constitution and structure of main group element complexes can be predicted and rationalised by a
More informationA pure covalent bond is an equal sharing of shared electron pair(s) in a bond. A polar covalent bond is an unequal sharing.
CHAPTER EIGHT BNDING: GENERAL CNCEPT or Review 1. Electronegativity is the ability of an atom in a molecule to attract electrons to itself. Electronegativity is a bonding term. Electron affinity is the
More informationVSEPR Model. The Valence-Shell Electron Pair Repulsion Model. Predicting Molecular Geometry
VSEPR Model The structure around a given atom is determined principally by minimizing electron pair repulsions. The Valence-Shell Electron Pair Repulsion Model The valence-shell electron pair repulsion
More informationC has 4 valence electrons, O has six electrons. The total number of electrons is 4 + 2(6) = 16.
129 Lewis Structures G. N. Lewis hypothesized that electron pair bonds between unlike elements in the second (and sometimes the third) row occurred in a way that electrons were shared such that each element
More information18 electron rule : How to count electrons
18 electron rule : How to count electrons The rule states that thermodynamically stable transition metal organometallic compounds are formed when the sum of the metal d electrons and the electrons conventionally
More informationLaboratory 11: Molecular Compounds and Lewis Structures
Introduction Laboratory 11: Molecular Compounds and Lewis Structures Molecular compounds are formed by sharing electrons between non-metal atoms. A useful theory for understanding the formation of molecular
More information3. What would you predict for the intensity and binding energy for the 3p orbital for that of sulfur?
PSI AP Chemistry Periodic Trends MC Review Name Periodic Law and the Quantum Model Use the PES spectrum of Phosphorus below to answer questions 1-3. 1. Which peak corresponds to the 1s orbital? (A) 1.06
More informationExercises Topic 2: Molecules
hemistry for Biomedical Engineering. Exercises Topic 2 Authors: ors: Juan Baselga & María González Exercises Topic 2: Molecules 1. Using hybridization concepts and VSEPR model describe the molecular geometry
More informationSample Exercise 12.1 Calculating Packing Efficiency
Sample Exercise 12.1 Calculating Packing Efficiency It is not possible to pack spheres together without leaving some void spaces between the spheres. Packing efficiency is the fraction of space in a crystal
More informationElectronegativity and Polarity
and Polarity N Goalby Chemrevise.org Definition: is the relative tendency of an atom in a molecule to attract electrons in a covalent bond to itself. is measured on the Pauling scale (ranges from 0 to
More informationCHEM 101 Exam 4. Page 1
CEM 101 Exam 4 Form 1 (White) November 30, 2001 Page 1 Section This exam consists of 8 pages. When the exam begins make sure you have one of each. Print your name at the top of each page now. Show your
More informationChemical Bonding: Covalent Systems Written by Rebecca Sunderman, Ph.D Week 1, Winter 2012, Matter & Motion
Chemical Bonding: Covalent Systems Written by Rebecca Sunderman, Ph.D Week 1, Winter 2012, Matter & Motion A covalent bond is a bond formed due to a sharing of electrons. Lewis structures provide a description
More informationUV-Vis spectroscopy Basic theory
UV-Vis spectroscopy Basic theory Dr. Davide Ferri Empa, Lab. for Solid State Chemistry and Catalysis 044 823 46 09 davide.ferri@empa.ch Importance of UV-Vis in catalysis IR Raman NMR XAFS UV-Vis EPR 0
More informationCHEM 1301 SECOND TEST REVIEW. Covalent bonds are sharing of electrons (ALWAYS valence electrons). Use Lewis structures to show this sharing.
CEM 1301 SECOND TEST REVIEW Lewis Structures Covalent bonds are sharing of electrons (ALWAYS valence electrons). Use Lewis structures to show this sharing. Rules OCTET RULE an atom would like to have 8
More informationWhich substance contains positive ions immersed in a sea of mobile electrons? A) O2(s) B) Cu(s) C) CuO(s) D) SiO2(s)
BONDING MIDTERM REVIEW 7546-1 - Page 1 1) Which substance contains positive ions immersed in a sea of mobile electrons? A) O2(s) B) Cu(s) C) CuO(s) D) SiO2(s) 2) The bond between hydrogen and oxygen in
More informationMolecular Structures. Chapter 9 Molecular Structures. Using Molecular Models. Using Molecular Models. C 2 H 6 O structural isomers: .. H C C O..
John W. Moore onrad L. Stanitski Peter. Jurs http://academic.cengage.com/chemistry/moore hapter 9 Molecular Structures Stephen. oster Mississippi State University Molecular Structures 2 6 structural isomers:
More informationStructures and Properties of Substances. Introducing Valence-Shell Electron- Pair Repulsion (VSEPR) Theory
Structures and Properties of Substances Introducing Valence-Shell Electron- Pair Repulsion (VSEPR) Theory The VSEPR theory In 1957, the chemist Ronald Gillespie and Ronald Nyholm, developed a model for
More informationSolid State Theory Physics 545
Solid State Theory Physics 545 CRYSTAL STRUCTURES Describing periodic structures Terminology Basic Structures Symmetry Operations Ionic crystals often have a definite habit which gives rise to particular
More informationMolecular Geometry and Chemical Bonding Theory
Chapter 10 Molecular Geometry and Chemical Bonding Theory Concept Check 10.1 An atom in a molecule is surrounded by four pairs of electrons, one lone pair and three bonding pairs. Describe how the four
More informationHealth Science Chemistry I CHEM-1180 Experiment No. 15 Molecular Models (Revised 05/22/2015)
(Revised 05/22/2015) Introduction In the early 1900s, the chemist G. N. Lewis proposed that bonds between atoms consist of two electrons apiece and that most atoms are able to accommodate eight electrons
More information5. Structure, Geometry, and Polarity of Molecules
5. Structure, Geometry, and Polarity of Molecules What you will accomplish in this experiment This experiment will give you an opportunity to draw Lewis structures of covalent compounds, then use those
More informationSection Activity #1: Fill out the following table for biology s most common elements assuming that each atom is neutrally charged.
LS1a Fall 2014 Section Week #1 I. Valence Electrons and Bonding The number of valence (outer shell) electrons in an atom determines how many bonds it can form. Knowing the number of valence electrons present
More informationLesson 3. Chemical Bonding. Molecular Orbital Theory
Lesson 3 Chemical Bonding Molecular Orbital Theory 1 Why Do Bonds Form? An energy diagram shows that a bond forms between two atoms if the overall energy of the system is lowered when the two atoms approach
More informationCHAPTER 6 REVIEW. Chemical Bonding. Answer the following questions in the space provided.
Name Date lass APTER 6 REVIEW hemical Bonding SETIN 1 SRT ANSWER Answer the following questions in the space provided. 1. a A chemical bond between atoms results from the attraction between the valence
More informationSOME TOUGH COLLEGE PROBLEMS! .. : 4. How many electrons should be shown in the Lewis dot structure for carbon monoxide? N O O
SME TUGH CLLEGE PRBLEMS! LEWIS DT STRUCTURES 1. An acceptable Lewis dot structure for 2 is (A) (B) (C) 2. Which molecule contains one unshared pair of valence electrons? (A) H 2 (B) H 3 (C) CH 4 acl 3.
More informationResonance Structures Arrow Pushing Practice
Resonance Structures Arrow Pushing Practice The following is a collection of ions and neutral molecules for which several resonance structures can be drawn. For the ions, the charges can be delocalized
More informationChapter 8 Basic Concepts of the Chemical Bonding
Chapter 8 Basic Concepts of the Chemical Bonding 1. There are paired and unpaired electrons in the Lewis symbol for a phosphorus atom. (a). 4, 2 (b). 2, 4 (c). 4, 3 (d). 2, 3 Explanation: Read the question
More information1.15 Bonding in Methane and Orbital Hybridization
1.15 Bonding in Methane and Orbital Hybridization Structure of Methane tetrahedral bond angles = 109.5 bond distances = 110 pm but structure seems inconsistent with electron configuration of carbon Electron
More information6.5 Periodic Variations in Element Properties
324 Chapter 6 Electronic Structure and Periodic Properties of Elements 6.5 Periodic Variations in Element Properties By the end of this section, you will be able to: Describe and explain the observed trends
More informationChapter 1 Benzene Blues 27
hapter 1 Benzene Blues 27 The ybridization Model of Atoms in Molecules An important question facing chemists about 80 years ago, was, ow does one go from recently invented atomic orbitals to rationalizing
More informationCHEMISTRY 101 EXAM 3 (FORM B) DR. SIMON NORTH
1. Is H 3 O + polar or non-polar? (1 point) a) Polar b) Non-polar CHEMISTRY 101 EXAM 3 (FORM B) DR. SIMON NORTH 2. The bond strength is considerably greater in HF than in the other three hydrogen halides
More informationCHEMISTRY 1710 - Practice Exam #5 - SPRING 2014 (KATZ)
CHEMISTRY 1710 - Practice Exam #5 - SPRING 2014 (KATZ) Name: Score: This is a multiple choice exam. Choose the BEST answer from the choices which are given and write the letter for your choice in the space
More informationB) atomic number C) both the solid and the liquid phase D) Au C) Sn, Si, C A) metal C) O, S, Se C) In D) tin D) methane D) bismuth B) Group 2 metal
1. The elements on the Periodic Table are arranged in order of increasing A) atomic mass B) atomic number C) molar mass D) oxidation number 2. Which list of elements consists of a metal, a metalloid, and
More informationCHAPTER 10 THE SHAPES OF MOLECULES
ATER 10 TE AE MLEULE EMIAL ETI BED READIG RBLEM B10.1 lan: Examine the Lewis structure, noting the number of regions of electron density around the carbon and nitrogen atoms in the two resonance structures.
More informationTopics. Coordination Compounds. Lewis Acid/Base Adducts Definitions complexes, ligands, coordination number
Topics Introduction Molecular Structure and Bonding Molecular Symmetry Coordination Compounds Electronic Spectra of Complexes Reactions of Metal Complexes Organometallic Chemistry Coordination Compounds
More informationCH101/105, GENERAL CHEMISTRY LABORATORY
CH101/105, GENERAL CHEMITRY LABORATORY LABORATORY LECTURE 5 EXPERIMENT 5: LEWI TRUCTURE AND MOLECULAR HAPE Lecture topics I. LEWI TRUCTURE a) calculation of the valence electron numbers; b) choosing the
More informationCHAPTER 6 Chemical Bonding
CHAPTER 6 Chemical Bonding SECTION 1 Introduction to Chemical Bonding OBJECTIVES 1. Define Chemical bond. 2. Explain why most atoms form chemical bonds. 3. Describe ionic and covalent bonding.. 4. Explain
More informationSection 11.3 Atomic Orbitals Objectives
Objectives 1. To learn about the shapes of the s, p and d orbitals 2. To review the energy levels and orbitals of the wave mechanical model of the atom 3. To learn about electron spin A. Electron Location
More informationCHAPTER 12: CHEMICAL BONDING
CHAPTER 12: CHEMICAL BONDING Active Learning Questions: 3-9, 11-19, 21-22 End-of-Chapter Problems: 1-36, 41-59, 60(a,b), 61(b,d), 62(a,b), 64-77, 79-89, 92-101, 106-109, 112, 115-119 An American chemist
More informationNuclear reactions determine element abundance. Is the earth homogeneous though? Is the solar system?? Is the universe???
Nuclear reactions determine element abundance Is the earth homogeneous though? Is the solar system?? Is the universe??? Earth = anion balls with cations in the spaces View of the earth as a system of anions
More informationPolarity. Andy Schweitzer
Polarity Andy Schweitzer What does it mean to be polar? A molecule is polar if it contains + and somewhere in the molecule. Remember: Protons can not move. So for a molecule to get a +/- it must somehow
More informationCHAPTER 13 CHAPTER 13. Generated by Foxit PDF Creator Foxit Software http://www.foxitsoftware.com For evaluation only.
Generated by Foxit PDF reator Foxit Software Pd- AND f-blk RGANETALLIS PAn organometallic compound must contain P a carbon-metal bond. PBook, p. 459, gives list of common ligands P An over-view of organometallics
More informationConjugation is broken completely by the introduction of saturated (sp 3 ) carbon:
Conjugation. Conjugation relies on the partial overlap of p-orbitals on adjacent double or triple bonds. ne of the simplest conjugated molecules is 1,3-butadiene. Conjugation comes in three flavors, the
More informationGeometries and Valence Bond Theory Worksheet
Geometries and Valence Bond Theory Worksheet Also do Chapter 10 textbook problems: 33, 35, 47, 49, 51, 55, 57, 61, 63, 67, 83, 87. 1. Fill in the tables below for each of the species shown. a) CCl 2 2
More informationMatter, Materials, Crystal Structure and Bonding. Chris J. Pickard
Matter, Materials, Crystal Structure and Bonding Chris J. Pickard Why should a theorist care? Where the atoms are determines what they do Where the atoms can be determines what we can do Overview of Structure
More informationACE PRACTICE TEST Chapter 8, Quiz 3
ACE PRACTICE TEST Chapter 8, Quiz 3 1. Using bond energies, calculate the heat in kj for the following reaction: CH 4 + 4 F 2 CF 4 + 4 HF. Use the following bond energies: CH = 414 kj/mol, F 2 = 155 kj/mol,
More information9.7 MOLECULAR ORBITALS
368 CHAPTER 9 Molecular Geometry and Bonding Theories John Barbaro, Orbital Bartending, J. Chem. Educ., Vol. 71, 1994, 1012. An analogy for orbital hybridization is suggested in this short article. Robert
More informationCHEMISTRY 113 EXAM 4(A)
Summer 2003 1. The molecular geometry of PF 4 + ion is: A. bent B. trigonal planar C. tetrahedral D. octahedral CHEMISTRY 113 EXAM 4(A) 2. The Cl-C-Cl bond angle in CCl 2 O molecule (C is the central atom)
More informationOCTET RULE Generally atoms prefer electron configurations with 8 valence electrons. - Filled s and p subshells
TYPES EMIAL BDIG 1 Ionic Bonding - Bond between ions whose charges attract each other - ne atom gives electrons and one atom takes electrons. Example a + l - ionic bond ovalent Bonding - two atoms each
More informationCHAPTER 10 THE SHAPES OF MOLECULES
ATER 10 TE AE MLEULE 10.1 To be the central atom in a compound, the atom must be able to simultaneously bond to at least two other atoms. e,, and cannot serve as central atoms in a Lewis structure. elium
More informationWe shall first regard the dense sphere packing model. 1.1. Draw a two dimensional pattern of dense packing spheres. Identify the twodimensional
Set 3: Task 1 and 2 considers many of the examples that are given in the compendium. Crystal structures derived from sphere packing models may be used to describe metals (see task 2), ionical compounds
More informationMolecular Geometry and Bonding Theories
9 Molecular Geometry and Bonding Theories We saw in hapter 8 that Lewis structures help us understand the compositions of molecules and their covalent bonds. owever, Lewis structures do not show one of
More information