Intermolecular forces Flashcards
What are intermolecular forces?
Forces which act between molecules but are weaker than covalent, metallic or ionic bonds
What molecules do Van der Waals act upon?
all molecules
In a Van der Waal, what happens when all of the electrons in the cloud are on one side?
it induces a temporary dipole as the two atoms are momentarily attracted to each other
In Van der Waals, do electron clouds move slowly or quickly?
Quickly
Why are the dipoles created in van der Waals temporary?
Because the electrons are always moving
What size molecules have stronger van der Waals forces and why?
Larger molecules
They have a larger electron cloud
What shape molecules cause stronger van der Waals?
Long and straight
What type of molecule do van der Waals occur between?
Non polar
Molecules of atoms which have the same amount of electronegativity as the electrons are equally shared
What type of molecules do dipole dipole occur between?
Polar
Molecules which have an unequal distribution of electrons
Are dipole dipole forces temporary or permanent?
Permanent
In hydrogen chloride gas (H-Cl), which molecule would be delta negative and why?
Chlorine
It is more electronegative so it attracts more electrons, giving it an overall negative charge
What is the amount of force which dipole dipole forces can range within?
5kJ to 20kJ
Which intermolecular force is the strongest?
Hydrogen bonding
Which intermolecular force is the weakest?
Van der Waals
What are the only three molecules which hydrogen bond to and why?
Fluorine (H-F)
Nitrogen (H-N)
Oxygen (H-O)
This is because they are the most electronegative
In a water molecule, what part is attracted to the hydrogen to form the bond?
Oxygens lone pair
What effect does hydrogen bonding have on molecules and why?
Higher melting and boiling points
More energy is required to break the bonds
