IB SL Chemistry - Polarity / IMF

• Polarity determines whether there is an overall positive/negative end to a molecule.
• Dipole: bond/molecule with ends of opposite charges (e.g., CO).
• Dipole moment: product of the charges/length of each dipole; shows the overall direction of electron pull.
• CO2 -> O=C=O -> no net dipole moment.
• H2O -> H-O-H with bent shape -> net dipole (molecule is polar).
• London forces: temporary attractive force due to formation of temporary dipoles in a nonpolar molecule.
• Dipole-dipole: similar to london forces; however, they describe the attraction between polar molecules.
• Hydrogen bonding: special type of dipole-dipole attraction. Result of hydrogen atom covalently bonded to very electronegative atom.
• VSEPR (Valence Shell Electron Pair Repulsion) Theory: essentially, extra electron pairs are drawn as separate “atoms”; the net number of electron pairs and atoms determine the structure.
• 3: Linear -> Linear.
• 4: Trigonal planar -> Trigonal planar, bent.
• 5: Tetrahedral -> Tetrahedral, trigonal pyramidal, bent.
• Trigonal bipyramidal -> Trigonal bipyramidal, sawhorse, t-shaped, linear.
• 7: Octahedral -> Octahedral, square pyramidal, square planar, t-shaped, linear.