Chapter 10 Chemical Bonding II: Molecular Shapes, Valence Bond Theory, and Molecular Orbital TheoryValence Shell Electron Pair Repulsion Theory5 Basic Arrangements of Electron Groups about a Central AtomElectron groups=2 LinearElectronic geometry vs Molecular GeometryElectron groups= 3 Electron Geometry = Trigonal PlanarElectron groups= 4 Electron Geometry = TetrahedralLone Pairs Have Greater electron-electron Repulsion than bonding groups.Lone Pair Effect on GeometryElectron groups= 5 Electron Geometry: Trigonal bipyramidalPowerPoint PresentationElectron groups = 6 OctahedralSlide 13Slide 14More Than One Central AtomSlide 16Polarity of MoleculesMolecule PolaritySlide 19Slide 20Slide 21Slide 22More Advanced Theories of Covalent BondingOrbital InteractionSigma bondsPi BondsCarbons s and p Atomic Orbitals Predict the Wrong Bonding and GeometryHybridizationSlide 29Orbital Diagram of the sp3 Hybridization of CMethane Formation with sp3 COrbital HybridizationAmmonia Formation with sp3 NSlide 34sp2 hybridizationSlide 36Slide 37sp HybridizationSlide 39Slide 40Chapter 10 1Chapter 10Chemical Bonding II: Molecular Shapes, Valence Bond Theory, and Molecular Orbital TheoryGeorgia Gwinnett CollegeChem 1212KFall 2013Chapter 10 2Valence Shell Electron Pair Repulsion Theory•VSEPR–A way of predicting molecular structures from the localized electron model.–The structure around a given atom is determined principally by minimizing electron-pair repulsions.•The lone and bonding pairs should be located as far from one another as possible.•The geometry is determined by the electron groups of the central atom.–The number of electron groups is equal to the sum of the bonded atoms and lone pairs about a central atom.–A double/triple bond only counts as 1 bonded atom.Chapter 10 35 Basic Arrangements of Electron Groups about a Central AtomElectron groupsChapter 10 4Electron groups=2LinearExamples:CS2, HCN, BeF2Chapter 10 5Electronic geometry vs Molecular Geometry•Electronic geometry does not differentiate between electrons in bonds and lone pairs.•However, differentiating between lone pairs and bonding electrons is quite important to the shape of the molecule. This is also called the molecular geometry.Chapter 10 6Electron groups= 3Electron Geometry = Trigonal PlanarExamples:SO3, BF3, NO3-, CO32- Examples:SO2, O3, PbCl2, SnBr2 Electron Group ArrangementMolecular Geometryor ShapeChapter 10 7Electron groups= 4Electron Geometry = TetrahedralExamples:CH4, SiCl4, SO42-, ClO4-NH3PF3ClO3H3O+H2OOF2SCl2Chapter 10 8Lone Pairs Have Greater electron-electron Repulsion than bonding groups.Chapter 10 9Lone Pair Effect on GeometryChapter 10 10Electron groups= 5Electron Geometry: Trigonal bipyramidalSF4XeO2F2IF4+IO2F2-ClF3BrF3XeF2I3-IF2-PF5AsF5SOF4Chapter 10 11Chapter 10 12Electron groups = 6OctahedralSF6IOF5BrF5TeF5-XeOF4XeF4ICl4-1314Chapter 10 15More Than One Central AtomethaneCH3CH3ethanolCH3CH2OHChapter 10 16More Than One Central Atom•Determine the shape around each of the central atoms in acetone, (CH3)2C=O.C C COHHHHHH17Polarity of Molecules•In order for a molecule to be polar, it must have1) polar bonds•electronegativity difference—theory•bond dipole moments—measured2) an unsymmetrical shape•vector addition•Polarity affects the intermolecular forces of attraction.–therefore boiling points and solubilities•like dissolves like•nonbonding pairs affect molecular polarity; they pull the electron density stronglyChapter 1018Molecule PolarityThe H–Cl bond is polar. The bonding electrons are pulled toward the Cl end of the molecule. The net result is a polar molecule.Chapter 10Chapter 10 1920Molecule PolarityThe O–C bond is polar. The bonding electrons are pulled equally toward both O ends of the molecule. The net result is a nonpolar molecule.Chapter 1021Molecule PolarityThe H–O bond is polar. Both sets of bonding electrons are pulled toward the O end of the molecule. The net result is a polar molecule.Chapter 1022Molecule PolarityThe H–N bond is polar. All the sets of bonding electrons are pulled toward the N end of the molecule. The net result is a polar molecule.Chapter 1023More Advanced Theories of Covalent Bonding•Apply Quantum Mechanics to Molecules–Valence Bond Theory.•We will be introduced to this theory–Molecular Orbital Theory.•Unfortunately, we don’t have time.Chapter 10MO Theory is AWESOME. TAKE P-CHEM!!!!MO Theory is AWESOME. TAKE P-CHEM!!!!24Orbital Interaction•As two atoms approach, the partially filled or empty valence atomic orbitals on the atoms interact to form molecular orbitals.•Covalent bonds are the result of the OVERLAP of atomic orbitals.•The shapes of the atomic orbitals are important.–s-orbitals–px, py, and pz orbitalsChapter 10Sigma bonds25Pi BondsChapter 10 2627Carbons s and p Atomic Orbitals Predict the Wrong Bonding and GeometryChapter 1028Hybridization•Some atoms hybridize their orbitals to maximize bonding.–Hybridizing is mixing different types of orbitals to make a new set of degenerate orbitals.–sp, sp2, sp3, sp3d, sp3d2•Same type of atom can have different hybridizations depending on the compound.–C = sp, sp2, sp3Chapter 1029Chapter 1030Orbital Diagram of the sp3 Hybridization of CChapter 1031Methane Formation with sp3 CChapter 1032Orbital Hybridization•The number of electron groups can be used to determine the orbital hybridization.–2 electron groups: sp–3 electron groups: sp2–4 electron groups: sp3Chapter 1033Ammonia Formation with sp3 NChapter 1034Chapter 10sp2 hybridization36Chapter 1037Chapter 10sp Hybridization39Chapter 1040Determine the hybridization of the interior atoms.C1 = tetrahedral C1 = sp3C2 = trigonal planar C2 = sp2Sketch the molecule and orbitals.Example: Predict the hybridization and bonding scheme for