intramolecular forces vs intermolecular forces. intramolecular forces there are 2 types of...
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Intramolecular Forces
vsIntermolecular
Forces
Intramolecular ForcesThere 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
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
H-bonds & Dipole-DipoleRemember: 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
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!
Hydrogen bondsWhat do you need?
A hydrogen atom covalently bonded to an electronegative atom … N, O or F.
If only one of these conditions is met, you don’t get H-bonds
A lone pair of electrons on the electronegative atom.
Polar Covalent bond
London Dispersion Forcesaka “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
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.
REFLECTION:•On the LEFT side of your
notes:–List the different types of bonds•STRONGEST on top•WEAKEST on bottom
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