Intermolecular forces

Intermolecular forces

Attractive or repulsive forces between. That range from weak to strong

Dispersion forces

The weakest molecular force that are always present between molecules no matter their polarity. They are caused by temporary dipoles or instantaneous dipoles in the molecules. These are the result of random movement of the electrons surrounding the molecule

Strength of dispersion forces

Strength of dispersion forces increase as the size of the molecule increase. This is because it is easier to produce temporary dipoles with a large number of electrons.

Effectivement of dispersion on mp/bp

Larger molecules have stronger dispersion forces resulting in them having higher melting and boiling points

As the molar mass increase

The strength of dispersion forces increases

As the number of electrons increase

The strength of dispersion forces increase

As the strength of dispersion increase

The boiling point increases

Molecular shape and dispersion forces

Molecules with longer chains tend to have stronger dispersion forces than compact molecules with similar number of electrons.

Molecular shape and dispersion forces

The greater the spread of electrons in a molecule, the stronger the dispersion forces and the higher the boiling point

Dipole dipole forces

Only occur in polar molecules. These forces result from the attraction between the positive and negative dipoles of the polar molecules. The more polar a molecule is, the stronger the dipole-dipole forces.

Dipole dipole forces and mp/bp

The stronger the dipole dipole forces the higher the melting and boiling points. Stronger dipole dipole forces require more energy to break these bonds and change the state of a substance

Hydrogen bonding

The Strongest intermolecular force, only occurs between molecules containing a hydrogen covalently bonded to an oxygen, a nitrogen or a fluorine atom.