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Molecular Geometry and Bonding Theories

• Predict 3-D shapes of molecules by using the VSEPR model (9.2)
• determine whether a molecule is polar or nonpolar based on its geometry and the individual bond dipole moments (9.3)
• explain the role of orbital overlap in the formation of covalent bonds (9.4)
• determine the hybridization atoms in molecules based on observed molecular structures (9.5)
• sketch how orbitals overlap to form sigma and pi bonds (9.6)
• explain the existence of delocalized pi bonds in molecules such as benzene. (9.6)

Molecular shapes

• the 3-D shapes and sizes of molecules are determined by the bond angles and bond lengths
• 5 basic shapes
• linear
• trigonal pyramidal
• tetrahedral
• trigonal bipyramidal
• octahedral
• Key Equation
• 1/2 (no. of bonding electrons - no. non-bonding electrons)
• Vocab
• BOND ANGLES: Angles made by lines joining the nuclei of the atoms in a molecule are the bond angles

The VSEPR Model

• The valence shell electron-pair repulsion model rationalizes molecular geometries based on the repulsions between electron domains.
• Bonding and non-bonding pairs of electrons both create electron domains around an atom
• Electron domains orient themselves to minimize repulsions, stay as far apart as possible.
• Non-bonding pairs give out slightly bigger repulsions than those of bonding pairs. which makes non-bonding pairs accustomed to certain positions.
• In a molecule with multiple central atoms we look at the geometry of each atom, so there's multiple molecular geometries
• VOCAB
• Electron domains: regions about a central atom in which electrons are likely to be found.
• Bonding Pairs: those involved in making bonds
• Non-bonding pairs: Lone pairs
• Electron Domain Geo: The arrangement of electrons around
• a central atom
• Molecular Geo: The arrangement of atoms

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