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Polar Bonds and Molecules Chapter 8.4
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If the difference in electronegativity is between
1.7 to 4.0: Ionic Bond 0.3 to 1.7: Polar Covalent Bond 0.0 to 0.3: Non-Polar Covalent Bond
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Electronegativity Scale
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Polar Covalent Bond vs Non-Polar Covalent Bond
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Polar Covalent vs Non-Polar Covalent
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Drawing Polar Bonds and Molecules
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Net Dipole of Molecules
Dipole – separation of charges within a molecule between two covalently bonded atoms. Net Dipole – When all the dipole vectors are summed to give one overall dipole.
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Attractions Between Molecules or Intermolecular Forces (IM Forces)
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We have already talked about intramolecular forces.
Intramolecular forces hold atoms together in a molecule. Covalent bonds would be an example. Intermolecular forces are attractive forces between molecules.
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Intermolecular Forces
Intramolecular = strong Intermolecular = weak They do control physical properties such as boiling and melting points, vapor pressure, and viscosity
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Types of Intermolecular Forces
van der Waals Forces Dipole-dipole interactions Ion-Dipole interactions London dispersion forces
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Dipole-Dipole Interactions
Molecules that have permanent dipoles are attracted to each other.
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Ion-Dipole Interactions
Attractive forces between an ion and a polar molecule Ion-Dipole Interaction The larger the charge the stronger the force
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London Dispersion Forces
Occasionally electrons wind up on the same side of the atom.
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London Dispersion Forces
At that instant, the helium atom is polar.
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London Dispersion Forces
This polar helium atom then induces a dipole on a neighboring helium atom.
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London Dispersion Forces
London dispersion forces, or dispersion forces, are attractions between an instantaneous dipole and an induced dipole.
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London Dispersion Forces
These forces are present in all molecules, whether they are polar or nonpolar. The tendency of an electron cloud to distort in this way is called polarizability.
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Types of Intermolecular Forces
Hydrogen Bonding The dipole-dipole interactions experienced when H is bonded to N, O, or F are unusually strong. We call these interactions hydrogen bonds.
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Hydrogen Bonding: Water
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Hydrogen Bonding: Water
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