UnitA - Intermolecular forces, spectrum, solubility

Define intermolecular bonds

Forces between molecules

What properties are intermolecular forces responsible for?

Physical properties and behaviour such as: melting/boiling point and solubility of substances

What is the difference between intra and inter molecular bonds?

Intra - bonds between atoms within a molecule

Inter - bonds between molecules

What are the 3 types of intermolecular forces? What are their electronegativities and polarity?

• London Dispersion Forces(weakest force)

  • lowest electronegativity difference

  • non-polar

• Dipole-dipole Forces(medium force)

  • medium electronegativity difference

  • polar

• Hydrogen Bonding(strongest force)

  • highest electronegativity difference

  • very polar

What kind of compounds have London forces?

All molecules

What determines a greater london dispersion force?

The larger the compound = more protons and electrons it has = greater the LDF = great boiling point

How do you know if the compound is dipole-dipole?

If the compound is polar, if it is non-polar, than no

What compounds have dipole-dipole forces?

• Polar molecules that are electrostatically attracted to one another

  • The greater the difference in electronegativities = the stronger the dipole

How do you know if the compound is hydrogen bonding?

If hydrogen is directly attached to fluorine, oxygen, or nitrogen

What compounds have hydrogen bonding?

H-F, H-O, H-N

How do you know if the compound has a high boiling point?

the bigger the compound = more protons and electrons = bigger the LDF = big boiling points

When determining which molecule has the biggest boiling point, but they are the same size, you should…

Look at how many different intermolecular forces it has

• If the compound 3 types of forces, it has the higher boiling point

How do e- act in non-polar bonds?

e- are held by equally sharing e- between atoms

How do e- act in polar bonds?

e- are shared unequally where e- are slightly towards one side

How do e- act in ionic bonds?

e- are dragged and transferred towards one side

What solvent are polar and non-polar solutes able to dissolve in?

• Like dissolves like

  • Polar things dissolve in polar compounds

  • Non-polar things dissolve in non-polar compounds