Intermolecular Forces Flashcards
What are intermolecular forces?
An attractive force between molecules
What are the 3 types of IMF?
London forces
Permanent dipole-dipole
Hydrogen bonding
Order of IMF in terms of weakest to strongest?
London forces- weakest
Permanent dipole-dipole
Hydrogen bonding- strongest
What do IMF affect?
Melting and boiling points
What are London forces?
Temporary induced dipole dipole forces
What type of molecules do London forces occur between?
Non-polar molecules
Are London forces always present in all molecular substances?
Yes
When do London forces occur?
Because the electrons are constantly moving around and there will be an uneven electron distribution at an given moment in time
This causes a temporary dipole within a molecule
Do London forces act for a long or short time?
Short time- the electron density is constantly changing
How do the strength of London forces increase?
The number of electrons in the molecule/atom increases
The surface contact of the molecules/atoms increases
What are permanent dipole-dipole forces?
Permanent dipole-dipole attractions between polar molecules
What is the definition of hydrogen bonding?
The interaction between the lone pair of electrons on a nitrogen, oxygen or fluorine atom and a hydrogen atom which is bonded to a N, O or F atom
Why do London forces get stronger as you go down the noble gases?
Atoms get larger and there are more electrons
Therefore stronger London forces
Boiling point increase
Why do the halogens boiling point increase as you go down the group?
Atoms and therefore the molecules get larger
There are more electrons
Stronger London forces
Higher melting and boiling points
What are polymers?
Very long molecules
