 So, carbon dioxide. Why is it important to learn about it? Well, it's a product of one of the most important chemical reactions in the world, combustion, which is how a lot of people in the world heat their homes and power their cars. It also unfortunately contributes to the greenhouse effect and global warming. If you want to learn more, here's a video from our channel just for you. The carbon dioxide molecule is formed from one carbon atom and two oxygens. Now both these elements are in row two of the periodic table and have two electron shells. They are happiest when they have a full outer shell or octet of electrons. As an element, carbon only has four outer shell electrons and oxygen six. We get double covalent bonds between the atoms where two electrons from each atom are shared, making four bonding electrons in total. We draw this with a double straight line, like so. The two groups of bonding electrons in carbon dioxide repel each other and this keeps the oxygen atoms as far away from each other as possible. Because of this, we can say that the carbon dioxide bond angle is 180 degrees. Knowing what you know about the bonding in a water molecule and a carbon dioxide molecule, which do you think is going to be more reactive? Again, pause the video and resume once you've had a think. Well, the answer is that carbon dioxide is the less reactive molecule. Because it has two bonds with each oxygen, you need a lot more energy to break the atoms apart. Think of the covalent bonds as thin wires. To cut a bond between carbon and oxygen in carbon dioxide, you'd need to cut through two wires, which would take more effort than just cutting through one. Its strong double bonds make it very stable. And so whenever there are stray carbon and oxygen atoms flying about, they love to get together and form carbon dioxide. But in one way, though, carbon dioxide bonds are similar to water bonds. So here's a final little challenge. Can you think what this similarity might be? Here's a hint. Oxygen is a very electronegative element, but carbon much less so. Pause and resume once you've thought about it. The answer is that, like water, the bonds are polar covalent, making the carbon atom delta positive and the oxygen delta negative. Although, unlike water, carbon dioxide is not a polar molecule overall. Its linear geometry means that the two polar bonds effectively cancel each other out. So did you work that one out? Let's sum up. Carbon dioxide is made from one carbon atom forming polar covalent bonds with two oxygens. These bonds are at 180 degrees to each other and are stronger than the bonds of a water molecule, making carbon dioxide more stable and unreactive than water.