 Let's explore how different atoms come together and form covalent bonds. To begin with, let's look at how carbon and oxygen can form a covalent bond. Well, carbon has atomic number six, which means it has six electrons. So just like before, if you write the electronic configuration two in the first shell, the remaining four in the second shell. Now this shell can accommodate eight, which means to fill it up, it needs four. If it needs four, it will share four. Okay. What about oxygen? Well, it's electronic configuration will be two, remaining six. The second shell can accommodate eight. So it needs two more to complete its outer shell. If it needs two, it's going to share two. So how will they form a bond? Well, this is going to share four, this is only going to share two. Oh, so what carbon can do now is it can share two with one oxygen atom and it can share the other two with another oxygen atom. So let's draw the dot structure over here. So one for carbon, but two for oxygen. One will draw this side and one will draw this side. Now if we start with carbon, carbon will share all four of its outer most electrons. Two with this one, so we'll put two here, two with this one, so we'll put two here. What about oxygen? Oxygen shares only two. So this oxygen will share only two. And since this is a different atom, we're going to show a different symbol dot to represent its electrons. And what about the remaining? There are remaining four, which we'll put over here, just like what we did in a previous video. And same thing over here. It's going to share two and the remaining four we'll put over here. So let's check. Oxygen has its six electrons, six electrons, carbon has its four electrons. But if you look at the total electrons over, they will eat, eat and eat. Everyone's happy. And so they are now covalently bonded. So carbon forms a double bond with one oxygen and another double bond with another oxygen. You see two pairs are being shared. And so that's how carbon dioxide exists in nature. Let's consider another pair. How will nitrogen and hydrogen form a bond? When you draw the dot structure yourself, why don't you pause and try? All right. So if you write down electronic configuration for nitrogen, we have two, then the remaining five. So over here, it needs three more to complete its eight. So it's going to share three. If it needs three, it will share three. What about hydrogen? Well, hydrogen just has one electron. And so in the first shell, it needs one more to complete the shell. So it needs one, it'll share one. So this is going to share three. This is going to share one. How will it work out? Oh, you know what it can do? Nitrogen can share with three hydrogens, one each. So that means we'll have three hydrogens. So let's draw the dot structure now. So one for nitrogen, and then we have three hydrogen. So one for hydrogen here, another one hydrogen here, and we can either put on top or on the bottom, whatever we want. Let's put here. Now hydrogen is going to share one of its electrons. So let's put dot across whatever you want. So let's put a dot here for hydrogen and nitrogen. It's going to share three electrons, one each with the hydrogen. And once nitrogen shares three, two are remaining, which we can put to itself. And let's check. We have nitrogen five, one, two, three, four, its own five. But total, it now has access to eight nitrogen is happy. Hydrogen has its own one, but totally it has two. So hydrogen is also happy. Everything is filled. This means nitrogen forms a single bond. Look at that a single bond with three hydrogen atoms, giving us an N H three. So this is how they covalently bond and this is ammonia. Let's do one last. What about carbon and hydrogen? Again, pause and try first. All right. So for carbon, we have two, four, needs four, so shares four. And hydrogen, as we just saw, just one needs one, so shares one. How will it work out? Oh, carbon, since it's going to share four, but hydrogen can only share one. It's going to share one each with four hydrogens, which means now four hydrogens will bond with one carbon. OK, so one for carbon and four for hydrogen. First one, second one, third one and fourth one. And we can now quickly draw that dot one dot hydrogen is going to share whatever one it has with it. So that goes into sharing carbon is going to share all four one each with the hydrogen. So one here, one here, one here and one here. And so what we find is that carbon forms a single bond with four hydrogens, giving us C H four. This is called methane. But what's important is that we figured out how they covalently bond with each other.