 There are so many awesome things around us, and all of these are made up of atoms. But have you ever wondered what makes these tiny atoms stick together in this shape? Well, that happens because of different kinds of chemical bonds between these atoms. And today we are going to talk about one of them, covalent bond. Basically, these are chemical bonds where atoms mutually share electrons to be together. Now in the video of ionic bond, we have seen how atoms can lose electron and gain electron and get oppositely charged and attract each other, stick to each other. That makes sense, right? But how can atoms stick together by just sharing of electrons? Let's find out. So let's take a fluorine molecule for example. See one molecule of fluorine has two atoms of fluorine, and these two atoms are sticking together. Now let's see how these atoms are sticking together. Are they losing electron and gaining electron, or something else is happening here? So for this, let's write down the atomic number of fluorine, which is 9. That means a neutral atom of fluorine will have 9 electrons going around it. And its electronic configuration will be 2,7. That means there are 7 electrons in its outer most shell. Now let's draw the outer most electrons over here. And here we are only going to draw the outer most electrons, because you know, in a chemical reaction, only the outer most electrons participate. Only they are lost or gained, okay? So there is no need to draw the inner most electrons. So 7 in the outer most shell. So 7 crosses. Yes, I am representing the electrons with crosses here. Similarly, over here, 7 crosses. Now see, we know that atoms, they want to become more stable, more stable like noble gases. And noble gases, most of the noble gases, have 8 electrons in their outer most shell. So even these two fluorine atoms will want 8 electrons in their outer most shell. Currently they have only 7. Now which one will lose and which one will gain? Will that even happen? Let's see. If this fluorine atom loses an electron to this one, see this atom will have 8 electrons, but this one would have lost one. It has only 6. So this is not stable, right? Even though this is stable and happy, this is not going to be stable. So this kind of business is not going to happen between them. Nobody is going to lose or gain electron in this molecule. So how are they sticking together? Well, in this case, they are sharing electrons. Both these atoms are sharing one-one electron with each other, something like this. So what happens in this case is that this electron of this fluorine is not only going around this fluorine atom, but after being shared, it is going around both the fluorine atoms. Similarly, this electron of this fluorine is not only going around this fluorine atom, but now after being shared, it is going around both the fluorine atoms. So basically these two shared electrons from one from each of the fluorine is not only bound to one of these fluorine atoms, but now they are going around both of these fluorine atoms. Now you might be wondering how does that help? See if you just focus on this fluorine then see it has six electrons bound to just itself and now these two electrons are also going around it. So this fluorine atom experiences six plus two electrons around itself meaning eight electrons around itself and that's why it will find itself to be stable and happy. Now similarly if you focus just on this fluorine. Now it has six electrons bound to itself and now these two shared electrons they are also going around it. So this fluorine atom experiences eight electrons six plus two eight electrons around itself. So this is stable and this will find itself to be happy. So this is how by sharing one one electrons both of these atoms can complete their octate and become stable. Now let me explain you the sharing part with one more analogy. Let's say you and I are dog lovers and both of us have seven dogs each but for some weird reason we both will be extremely happy if we get to play with eight dogs each. Now how can that happen? So for that we both can share one one dog with each other something like this. See now these two shared dogs they are not bound to play with just me or just you but they will be playing with the both of us okay. Now in this case if you just focus on me then see I have six dogs which will just play with me but these two shared dogs are also available for me right. So I experience that I have eight dogs to play with six plus two eight dogs to play with so I am extremely happy. Now similarly if we just focus on you you have these six dog just to play with you and now these two dogs are shared so that means even you can play with them that means you will also experience six plus two eight dogs to play with and that's where you will be extremely happy okay. Now this is how by sharing our dogs we both get to be happy. Now see if we want to be happy always then we'll have to stick together and keep on sharing our dogs right. So in this case I can say that you and I have bonded together. Now something similar is happening even with the fluorine molecule. Here the fluorine atoms had seven electron and needed one more to be stable. To gain one it had to share one electron with each other okay. That's how they became stable. Now see if they want to be stable forever they will have to keep on sticking to each other and sharing one electron with each other right. So this is how a chemical bond is formed between these two fluorine atoms and now since this chemical bond is being formed because of sharing of electrons we call this a covalent bond. See co refers to sharing and valent refers to valence electrons and here the valence electrons are being shared right. That's why it's called covalent bond okay one last thing. See to represent a covalent bond simply without these crosses and circles we can draw a dash between the two sharing atoms just like this. One single dash refers to a pair of electrons or two electrons being shared between these two. So these two electrons can be replaced by a single dash and this means that these two atoms have a covalent bond a single covalent bond between them. Now let's look at couple of more examples to understand this concept a little better. This time let's talk about oxygen. Oxygen has eight electrons going around it and if I write its electronic configuration it will be 2,6. That means there are six electrons in the outer most shell. Let me draw it and show it to you. So this is the oxygen atom and here there are six crosses representing six electrons. Now see its octet is not complete. It does not have eight electrons in its outer most shell. That means it is not stable. Now how can it share electrons with another oxygen atom to have complete octet so that both of them have complete octet. Can you pause the video over here and try to figure this out? How many electrons will be shared between these two oxygen atoms? Now if you have thought about it let's see. So if you thought that they will be sharing one electrons let's see what happens. If both of them share one of their electrons then see this oxygen atom had six already and now it will have access to one electron from here. That means six plus one seven. So that means the octet is still not complete. So just sharing one electron is not going to help. This time they will have to share two of their electrons with each other. Something like this. Let's move this. Yes. So now you can see that this oxygen it had six electrons and now it has access to two more. That means its octet is complete. There are eight electrons for this oxygen. Similarly for this oxygen there are six plus two eight electrons. So its octet is also complete. So this time each the each atom had to share two electrons with each other to complete each other's octet and now both of them are stable. So here in this case since there are two pairs of electrons getting shared. One this and one this. We say that there are two covalent bonds between two oxygen atoms. So if we have to write this in simple terms we will say that between two oxygen atoms there are two covalent bonds. There is a double covalent bond here whereas in case of fluorine we saw a single covalent bond. Now let's look at one more example. So this time let's talk about nitrogen. So nitrogen has seven electrons in total. So its electronic configuration will be two comma five. That means it has five electrons in its outer motion. That means its octet is not yet complete. Now can you pause the video and try to draw it by yourself and show how many electrons will be shared between two nitrogen atoms so that both of them have complete octet. Pause and try it by yourself first. Now if you have tried it let's see. So here I have one nitrogen atom and I am showing five electrons in the outermost shell and here I have second nitrogen atom. So see since one nitrogen atom needs three more electrons. It has five in the outermost five plus three will be eight. So it needs three more electron therefore it needs to share three electrons with the other nitrogen. Something like this yes now if you see carefully this nitrogen has five plus three eight electrons its octet is complete and similarly this nitrogen's octet is complete and this is how they will covalently exist. Now over here if we have to count the number of covalent bonds see there is one pair being shared here let me change the color one pair of electron second pair of electron and third pair of electron. So in total three pairs of electrons are being shared between two nitrogens. So over here we see that when two nitrogens share electron there is a triple covalent bond between them okay. So we saw that fluorine has single covalent oxygen has double covalent and nitrogen has triple covalent. Now one last question how does hydrogen share electron and this question is unique because hydrogen has just one electron and it does not follow the octet rule. It does not need to have eight electrons in its outer most shell to be stable but instead it follows duvet rule meaning it needs to have two electrons in its outer most shell to become stable. Now with this new information can you pause the video and think about how two hydrogen atoms share electrons to be stable. Now if you have tried it let's see so here I have one hydrogen atom and it has one electron and another hydrogen atom with another electron. Now we know that hydrogen needs two electrons to become stable. So in this case both of these atoms will share one one electron with each other something like this. See now this hydrogen atom has one of its own and then one being shared meaning total two electrons. So this will be stable its duet will be complete. Similarly this hydrogen will have two electrons around it. So its duet will also be complete and this is how they will share electrons by a single covalent bond. So here we will write hydrogen has a single covalent bond with another hydrogen and this is how H2 gas exists in nature. Now let's summarize the video. In this video we spoke about covalent bonds basically where atoms share electron to become stable and stick together. We saw that these bonds could be single covalent or double covalent or triple covalent bond. And the major underlying principle was that if atom needs one electron then it needs to share one electron. If it needs two electron then it needs to share two electrons. If it needs three then it needs to share three.