 Let's look at what happens when two water molecules come near each other. What I'd like you to imagine is that this is a little tiny hydrogen nuclei. This is an oxygen atom, another hydrogen. So hydrogen, remember, has that one electron that it's shared right here. So the electron is mostly right through here, and this electron is mostly right through here. And oxygen has two unshared pairs, so there's a, you don't see a physical object, but try to imagine there's a cluster of electrons right here and another cluster over here. So when these two molecules come near each other, these electrons over here from the oxygen are going to be attracted to that positive nucleus, so it's going to line up like that. If the molecule comes in near each other like this, they're going to repel each other and it's actually going to push that molecule away, and now they're attracted. So water, even though it's a very small molecule, is a liquid at room temperature because of this hydrogen-bonding attraction. Let's look at another example. These are two molecules of carbon dioxide. We have carbon and two oxygens. If you look at the carbon, all of the electrons are predominantly here in a sigma and a pi or in this area right here, okay? And then for the oxygen, you have electrons shared here and here and then you have the electron pairs over here. If we move two molecules near each other, the electrons from here, the oxygen in this oxygen are going to push them away. They're not going to be attracted. On this side, the electrons from this oxygen and that oxygen are going to push them away. There's not much electron here, but since we have a pi bond, since the electrons are out in this area right here, they're not going to be attracted at all. In fact, they're slightly repel. So what do you know about carbon dioxide? Carbon dioxide is a gas at room temperature because of its geometry and because of its shape. It's a lot bigger than our water, but the attraction from one molecule to another, which is intermolecular forces, are weaker for carbon dioxide than for our water.