Presentation on theme: "Section 8.4 Molecular Shapes"— Presentation transcript:
1Section 8.4 Molecular Shapes Summarize the VSEPR bonding theory.atomic orbital: the region around an atom’s nucleus that defines an electron’s probable locationPredict the shape of, and the bond angles in, a molecule.Define hybridization.VSEPR modelhybridizationThe VSEPR model is used to determine molecular shape.
2VSEPR ModelThe shape of a molecule determines many of its physical and chemical properties.Molecular geometry (shape) can be determined with the Valence Shell Electron Pair Repulsion model, or VSEPR model which minimizes the repulsion of shared and unshared electrons around the central atom.
3VSEPR Model (cont.)Electron pairs repel each other and cause molecules to be in fixed positions relative to each other.Unshared electron pairs also determine the shape of a molecule.Electron pairs are located in a molecule as far apart as they can be.
4Lone pairs repel more strongly than bonding pairs!!! VSEPR TheoryTypes of e- Pairs (around central atom)Bonding Areas - from bonds (single, double, triple) all count as one pairLone pairs - nonbonding e-Lone pairs repel more strongly than bonding pairs!!!
5Determining Molecular Shape Draw the Lewis Diagram.Tally up e- pairs on central atom.Single/double/triple bonds = ONE pair (AREA)Shape is determined by the # of bonding AREAS and LONE PAIRS.Know the 8 common shapes& their bond angles!
6Common Molecular Shapes e- Tally2 total2 bond areas0 lone pairsBeH2LINEAR180°
13Common Molecular Shapes e- Tally6 total6 bond areas0 lone pairsSF6OCTAHEDRAL90°
14F P F F 107° Examples TRIGONAL PYRAMIDAL 4 total 3 bond areas 1 lone pairTRIGONAL PYRAMIDAL107°
15ExamplesO C OCO22 total2 bond areas0 lone pairLINEAR180°
16HybridizationIs the process by which s, p, and d orbitals combine to form new identical orbitalsThe hybridization is equal to the total number of Bonding Areas and lone pairs around the central atom in the molecule.For example: water has two bonding areas and two lone pairs of electrons, so we need 4 total hybrid orbitals = one s orbital and three p orbitals = sp3
17Hybridization (cont.)Single, double, and triple bonds occupy only one hybrid orbital (CO2 with two double bonds forms an sp hybrid orbital).
21A B C D Section 8.4 Assessment The two lone pairs of electrons on a water molecule do what to the bond angle between the hydrogen atoms and the oxygen atom?A. They attract the hydrogen atoms and increase the angle greater than 109.5°.B. They occupy more space and squeeze the hydrogen atoms closer together.C. They do no affect the bond angle.D. They create resonance structures with more than one correct angle.ABCD
22A B C D Section 8.4 Assessment The sp3 hybrid orbital in CH4 has what shape?A. linearB. trigonal planarC. tetrahedralD. octahedralABCD