 Let's do this one now. It says show the reaction between oxygen and hydrogen to form the molecule water. So again, the first thing we're going to have to do is write the or draw the Lewis dot structures of the atoms hydrogen and oxygen. Okay, so if we look at where they are on the periodic table we'll know that hydrogen has one valence electron and oxygen has one, two, three, four, five, six valence electrons. Okay, so remember, so what are these elements hydrogen is a non-metal? So remember it can be on maybe it can be like a group one or a group 17 element. In this case it acts like a group 17 element and oxygen of course is a non-metal as well. So when we have two non-metals come together, what do we form? We form a covalent bond and unlike a covalent ionic bond, a covalent bond is the sharing of the electron. So these guys aren't going to actually transfer the electron like the last problem we did. They're going to share it. Okay, but the problem is here is hydrogen it only needs one electron to fill its valence shell but oxygen needs two. Hopefully you see that, right? So it's only got six to make an octet. It means eight. So in other words that should give you the clue as to say, well if this compound is made up of only hydrogen and oxygen, then there must be something that we're missing here. And the element that we must be missing is another hydrogen atom because we only need one more one more electron to fill up that space in oxygen. So again, we can draw these Lewis structures with the dot here, here, here, here, whatever is the most convenient to build your molecule. Okay, so since we've got these two non-metals coming together we're going to form a covalent bond like we said and remember since we're showing the motion of just one electron we'll do what we call these Fischer-keros and since we're doing a covalent molecule we'll show two of them, meaning in the middle, not transferring one to the other, but actually meaning in the middle. So they're actually each donating one electron to what we call this covalent bond that's going to be one. Just like here, donating one electron, one electron, if this helps you. Eventually, we won't show this anymore because this fish hook means the same thing. So when that happens, and again, they're not transferring them, they're sharing them, they're like holding hands now. So the oxygen and the hydrogen instead of having those dots they have a line between them like that and a line between them like that. This line is a covalent bond. That is, we didn't show anything like that in the ionic compounds that we made. Also, we've got these four electrons here on the oxygen that didn't do anything. They stayed the same. So we got to show them over here. So the oxygen now has eight electrons around it but some of the electrons are different than some of the other electrons. So it's got four electrons that are located in the two bonds because remember, bonds are made up of two electrons. These electrons, the four electrons that are in those bonds, we call bonding electrons, electrons. These are all in the valence shell. The oxygen we call, how many bonding electrons are there around the central atom? You would say four bonding electrons and how many non-bonding electrons you would say four and you shouldn't get pretty good at. This is known as the Lewis structure of the molecule. Eventually we'll show through Vesper theory what it really looks like in three dimensions and how to depict these types of molecules on a two-dimensional surface. So a molecule isn't flat like a piece of paper, but we have only chalkboards to write on until that event of technology, I guess, and now we can demonstrate models and stuff in three dimensions. But it's still very, very useful to be able to draw things in two dimensions and then depict them in three dimensions on a two-dimensional surface. So cool.