* Oxygen gas (O₂): This is the form we breathe. It consists of two oxygen atoms covalently bonded together, forming a diatomic molecule. These molecules are then weakly attracted to each other by van der Waals forces. This means the molecules are close together but not rigidly fixed in a lattice. They can move around freely, which is why oxygen is a gas at room temperature.

* Solid oxygen (O₂): At very low temperatures, oxygen gas condenses into a liquid, and then further into a solid. In solid oxygen, the diatomic molecules arrange themselves in a crystalline lattice structure. There are actually multiple crystal structures depending on the temperature and pressure.

Key takeaways:

* Oxygen gas (O₂): Diatomic molecules held together by weak intermolecular forces.

* Solid oxygen (O₂): Diatomic molecules arranged in a crystalline lattice.

Let me know if you would like to know more about the specific crystal structures of solid oxygen!