Unit 11 IMF

Strongest intramolecular force

Covalent (INTRA)

Weakest IMF

Dispersion forces

Strongest IMF

Ionic bonding (solids)

List IMFs in order from weakest to strongest (5)

Weakest: Dispersion forces

Dipole-dipole interactions

Hydrogen bonding

Ion-dipole interactions

Ionic bindings

What factors affect the amount of dispersion force in a molecule

• # of elections (more e more dispersion force)

• Size of atom

• Shape of molecules with similar masses (more compact, LESS dispersion force)

Describe dispersion forces

When a nonpolar particle can be temporarily polarized to allow dispersion force to form

• When the e from one atom interacts with nucleus of another atom

• All compounds exhibit dispersion forces

Define polarizability

The tendency of an electron cloud to distort

• “squishiness” of an e cloud

What are dipole-dipole interactions

• polar molecules have a more positive and a more negative ends creating a permanent dipole moment

• The oppositely charged ends attract each other

• Leads to stability in the condensed phase

What does polarity do to bolting point?

With molecules of equal mass and size, the more polar the molecule the higher the boiling point

What three atoms can be involved with hydrogen bonding

F, O, N

What is a hydrogen bond

An attraction between a H atom attached to a highly electronegative atom and a nearby small electronegative atom in another molecule or chemical group

What are ion-dipole interactions and what are they found in

• Found in solutions of ions

• The strength of these forces is what makes it possible for ionic substances to DISSOLVE IN POLAR SOLVENTS

• ions in nonpolar solvents wont dissolve

If ions are present and so are polar molecules what force is this?

Ion-dipole

If ions are present but there are no polar molecules what is this?

Ionic bonding

If ions are not present but polar molecules are

Dipole-dipole OR Hydrogen bonding if H atoms are bonded to N, O, or F atoms

Ions are not present and neither are polar molecules

Only dispersion forces

If two molecules are of comparable size and shape what interactions are most likely dominating

Dipole-dipole

What happens to IMFs when polarity increases

IMFs get stronger