Question

What are the intermolecular forces?

Answer 1

Intermolecular forces:
- Van der Waals forces: ion-dipole, dipole-dipole, ion-induced dipole, dipole-induced dipole, London dispersion forces
- Hydrogen bond

See below for definitions and examples which can help you with the determination.

Explanation:

Ion-dipole interaction
If an ion and a polar molecule interact the result is an ion-dipole interaction.
On the picture below the positive ion `Na^+` and negative part, id est the oxygen of the `H_2O` molecule, are next to one another.

Hydrogen bonding
H-bonding is the interaction between an electronegative atom like oxygen, nitrogen or fluorine and a hydrogen atom.
On this gif below you can see interactions between `H_2O` molecules. The hydrogen bond if formed between oxygen[red] and hydrogen[white].

Hydrogen bonds also appear bewtween `HF`, `NH_3`, amino acids, alcohols and between the chains of the DNA, id est. between its nucleobases.

Dipole-dipole interaction
Dipole-dipole interactions are electrostatic interactions between molecules which have permanent dipole. The positive end of a polar molecule will attract the negative end of the other polar molecule. An example of this interaction is the intermolecular interaction between two `HCl` molecules.

Ion-induced dipole interaction
Interactiton between an ion and a non-polar molecule. As you can see below the charge of the ion causes distortion of the electron cloud on the non-polar molecule. So we have an non-polar molecule in iteracttion with an ion and this ion produces a induced dipole/ polar molecule from a non-polar molecule.

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On the picture below there is an example of such interaction. We have a `Fe^ 2+` ion in the interaction with a non-polar molecule which becomes in this interaction an induced dipole as on the gif above.

Dipole-induced dipole interaction
A non-polar molecule turns into a induced dipole when it interacts with a polar molecule.

As a example we can take the interaction between the non-polar molecule `O_2` and the polar `H_2O` molecule. When they interact we have the same process as on the gif above.

London dispersion forces/ induced dipole- induced dipole interaction
London forces are interactions between non-polar molecules. There is an instantaneous dipole moment caused by the movement of the electrons that causes such interaction.

In the `Ne` atom the induced dipole in one atom influences the electron distribution in other atom and the atoms attract.

A brief summary of my answer: