ELI5. What’s between Molecules?

Question

I know things are made of molecules but what keeps molecules together? What’s between them?

In: 6

Answer 1

It depends. For most gases there is nothing between them. It is a vacuum.

For liquids and solids intermolecular distances are similar to intramolecular forces. For example in water oxygen’s electrons will have a probability of being between an oxygen nucleus and its own hydrogen nucleus (a covalent bond) and there will be a probability the electron will be between the oxygen nucleus and a neighbouring hydrogen nucleus (a hydrogen bond).

For metals intermolecular and intramolecular electron density is the same since a metal crystal acts as a macromolecule of a visible size.