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Intramolecular Forces vs Intermolecular Forces

Intramolecular Forces vs Intermolecular Forces. Intramolecular Forces. There are 2 types of attraction in molecules: int ra molecular bonds & int er molecular forces We have already looked at intramolecular bonds These are forces that hold atoms together to form molecules

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Intramolecular Forces vs Intermolecular Forces

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  1. Intramolecular Forces vsIntermolecular Forces

  2. Intramolecular Forces There are 2 types of attraction in molecules: intramolecular bonds & intermolecular forces • We have already looked at intramolecular bonds • These are forces that hold atoms together to form molecules • Examples:Ionic, Non-Polar Covalent, and Polar Covalent

  3. Intermolecular Forces • Intermolecular forces (IMF) have to do with the attraction between molecules There are 3 different levels of strength in IMFs • Hydrogen bonding (the strongest) • Dipole-dipole Forces • London Dispersion Forces (the weakest) POLAR NON-POLAR

  4. H-bonds & Dipole-Dipole Remember: POLAR BEARS DON’T SHARE FAIR • The unequal sharing in polar bonds cause a slight (+) charge on one atom, and a slight (-) charge on the other atom Dipole-Dipole

  5. So what’s a H-bond? • H-bonding is a special type of dipole - dipole attraction that is very strong • It occurs when N, O, or F are bonded to H Bonding Is FHON!

  6. Hydrogen bonds What do you need? A hydrogen atom covalently bonded to an electronegative atom … N, O or F. A lone pair of electrons on the electronegative atom. If only one of these conditions is met, you don’t get H-bonds

  7. Polar Covalent bond

  8. London Dispersion Forces aka “van der Waal” forces • Seen in non-polar molecules • Happen because partial charges can show up for just an instant (b/c e-s are moving) • This creates a temporary dipole • When e- leaves, the dipole is gone

  9. REMEMBER • All bonds are stronger than all intermolecular forces. • Molecules that use bonding only will have the strongest structures • Molecules that use bonding and intermolecular forces will have weaker structures, where the strength depends upon the type of intermolecular force used • Molecules that use intermolecular forces and no bonding will have the weakest structures known; examples of these would be Noble Gases.

  10. REFLECTION: • On the LEFT side of your notes: • List the different types of bonds • STRONGEST on top • WEAKEST on bottom

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