Figure 9.11: Potential-energy curve for H2.Slide 2Slide 3Figure 9.10: The electron probability distribution for the H2 molecule.Slide 5Slide 6Slide 7Slide 8Figure 9.14: The HCl molecule.Figure 9.12: Molecular model of nitro-glycerin.Slide 11Figure 9.9: Model of CHI3 Courtesy of Frank Cox.Slide 13Slide 14Slide 15Slide 16A model of ethylene.A model of acetylene.A model of COCl2.Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Figure 10.26: Sigma and pi bonds.Figure 10.27: Bonding in ethylene.Slide 47Figure 10.28: Bonding in acetylene.Slide 49Slide 50Slide 51Slide 52Slide 53Slide 54Slide 55Figure 9.11: Potential-energy curve for H2.Covalent Bonding in Hydrogen, H2Figure 9.10: The electron probability distribution for the H2 molecule.Covalent bondsanimationhttp://www.chem1.com/acad/webtext/chembond/cb03.htmlThis is a good overview.http://www.chem.ox.ac.uk/vrchemistry/electronsandbonds/intro1.htmFor elements larger than Boron, atoms usually react todevelop octets by sharing electrons. H, Li and Be striveto “look” like He. B is an exception to the noble gas paradigm.It’s happy surrounded by 6 electrons so the compound BH3 is stable.Try drawing a Lewis structure for methane.Draw Lewis dot structures for the halogens.Try oxygen and nitrogen.Notice that these all follow the octet rule!These also follow the octet rule!Bond Lengths and Covalent RadiusFigure 9.14: The HCl molecule.Figure 9.12: Molecular model of nitro-glycerin. What is the formula for thiscompound?Rules for drawing Lewis structures1. Count up all the valence electrons2. Arrange the atoms in a skeleton3. Have all atoms develop octets (except those around He)Figure 9.9: Model of CHI3Courtesy of Frank Cox.Make some Lewis Dot Structures with other elements:CH4 NH3H2OC2H6C2H6OCH2OLook at all these structures and make some bonding rules:The normal number of bonds that common elements make in covalent structures.Element # BondsCNOH, HalogensElement # BondsC 4N 3O 2H, Halogens 1Rules for drawing Lewis structures1. Count up all the valence electrons2. Arrange the atoms in a skeleton3. Have all atoms develop octets (except those around He)4. Satisfy bonding preferences!A model of ethylene.A model of acetylene.A model of COCl2.VSEPR: Valence Shell Electron Pair Repulsion:A way to predict the shapes of moleculesPairs of valence electrons want to get as far away from each other as possible in 3-dimensional space.Balloon Analogy for the MutualRepulsion of Electron GroupsTwo Three Four Five SixNumber of Electron GroupsAX2 Geometry - LinearCl ClBe..............1800BeCl2Gaseous beryllium chloride is an example of a molecule in which the central atom - Be does not have an octet of electrons, and is electron deficient.Other alkaline earth elements also have the same valence electron configuration, and the same geometry for molecules of this type. Therefore this geometry is common to group II elements.Molecular Geometry = Linear ArrangementCO O......1800Carbon dioxide also has the same geometry, and is a linear molecule, but in this case, the bonds between the carbon and oxygens are double bonds.CO2The Two MolecularShapes of theTrigonal PlanarElectron-GroupArrangementAX3 Geometry - Trigonal PlanarBF3BFF F..................NOO O120012001200NO3-Boron TrifluorideNitrate AnionAll of the boron Family(IIIA)elements have the same geometry. Trigonal Planar !AX2E SO2..........................SOOThe AX2E molecules have a pair ofElectrons where the third atom would appear in the space around the central atom, in the trigonal planargeometry.-The Three Molecular Shapesof the TetrahedralElectron-GroupArrangementAX4 Geometry - TetrahedralCHH HHCH4MethaneCHHHH109.50All molecules or ions with four electron groups around a central atomadopt the tetrahedral arrangementHHNHHHHH++109.50109.50NH..107.30all angles arethe same!Ammonia is in a tetrahedral shape, but it has only an electron pair in one location, so the smaller angle!Ammonium IonThe Four Molecular Shapes of the TrigonalBipyramidal Electron-Group ArrangementAX5 Geometry - Trigonal BipyramidalBrFFF......................86.20AX3E2 - BrF3III..................1800AX2E3 - I3-PClClClClCl..............................AX5 - PCl5The Three MolecularShapes of the Octahedral Electron-GroupArrangementAX6 Geometry - OctahedralSFFFFFF....................................AX6Sulfur HexafluorideIFF FFF.............................. .. AX5EIodine PentafluorideXeFFFF............................Xenon Tetrafluoride Square planar shapeUsing VSEPR Theory to Determine Molecular Shape1) Write the Lewis structure from the molecular formula to see the relative placement of atoms and the number of electron groups.2) Assign an electron-group arrangement by counting all electron groups around the central atom, bonding plus nonbonding.3) Predict the ideal bond angle from the electron-group arrangement and the direction of any deviation caused by the lone pairs or double bonds.4) Draw and name the molecular shape by counting bonding groups and non-bonding groups separately.Hybrid Orbital ModelThe sp Hybrid Orbitals in Gaseous BeCl2The sp3 Hybrid Orbitals in NH3 and H2OThe sp3d Hybrid Orbitals in PCl5The sp3d2 Hybrid Orbitals in SF6Sulfur Hexafluoride -- SF6Figure 10.26: Sigma and pi bonds.Figure 10.27: Bonding in ethylene.Figure 10.28: Bonding in acetylene.Restricted Rotation of -Bonded MoleculesA) Cis - 1,2 dichloroethylene B) trans - 1,2 dichloroethylenePostulating the Hybrid Orbitals in a MoleculeProblem: Describe how mixing of atomic orbitals on the central atoms leads to the hybrid orbitals in the following: a) Methyl amine, CH3NH2 b) Xenon tetrafluoride, XeF4Plan: From the Lewis structure and molecular shape, we know the number and arrangement of electron groups around the central atoms,from which we postulate the type of hybrid orbitals involved. Then we write the partial orbital diagram for each central atom before and after the orbitals are hybridized.Postulating the Hybrid Orbitals in a MoleculeProblem: Describe how mixing of atomic orbitals on the central atoms leads to the hybrid orbitals in the following: a) Methyl amine, CH3NH2 b) Xenon tetrafluoride, XeF4Plan: From the Lewis structure and molecular shape, we know the number and arrangement of