So now that we've introduced nonpolar covalent bonds in our previous lesson videos, in this video, we're going to introduce the second type of covalent bond which is the polar covalent bond. Now, once again, the word covalent here means the sharing of electrons, and so even in polar covalent bonds, there's going to be sharing of electrons, but the word polar here is really referring to the unequal sharing of electrons between atoms, and so polar covalent bonds are characterized by unequal sharing of electrons. Now the reason that the electrons are being shared unequally in polar covalent bonds is due to different electronegativities between the atoms. And so, what this means is that they are going to pull on the electrons with different amounts of strength. Now, of course, unequal sharing of electrons between atoms is going to lead to an unequal distribution of these negatively charged electrons, and an unequal distribution of negatively charged electrons is going to lead to partial charges.
And so this symbol right here is the Greek symbol delta, which can be used to symbolize the word partial, and so you'll see this symbol down below throughout our image. So, in our image over here on the left-hand side, we're showing you a few examples of polar covalent bonds, and so the first example that we're showing you is Hydrogen Chloride whose chemical formula is HCl. So you can see the hydrogen atom over here and the chloride atom over here. Now, hydrogen and chloride have very different electronegativities. Chloride pulls really, really hard on electrons.
It has a high electronegativity, but hydrogen does not pull very hard on electrons. It has a low electronegativity, So there is a big difference here in electronegativities between these two atoms. And so, what that means is that this bond that forms between them, which represents the sharing of 2 electrons, a pair of electrons because chlorine pulls harder on these 2 electrons, these 2 electrons are going to spend more time with the chlorine. And remember the electrons are negatively charged, so because these 2 negatively charged electrons spend more time with the chlorine because the chlorine pulls harder on these electrons because it's more electronegative, the chlorine is going to be associated with a partial negative charge because once again it's pulling these negatively charged electrons harder and so they spend more time with the chlorine and that's what gives the chlorine a partial negative charge. And the opposite happens to the hydrogen, the hydrogen does not pull as hard on the electron because it is not as electronegative.
And so it has these electrons, for less amount of time. And so, if you give up something that's negative, you therefore become more positive, so it gets a partial positive charge. And so, you can see how this unequal distribution of electrons, between the atoms, leads to partial charges. Now we can see something very similar if we take a look at a typical water molecule such as H₂O. It has 2 hydrogen atoms and one oxygen atom.
Now once again, oxygen is one of the most electronegative atoms that exist. It is super electronegative which means that it pulls on these electrons super hard. The hydrogen atoms on the other hand once again are not very electronegative, so they do not pull on electrons that hard at all. And so, of course, each of these lines that we see here represent a pair of electrons being shared between the atoms. So you can see down below we have a pair over here and a pair over here being shared.
And so because, once again, oxygen pulls really hard on these electrons that are being shared, those electrons are going to spend more time with the oxygen and because the electrons are negatively charged it gives the oxygen a partial negative charge. And once again, the hydrogens, on the other hand, are going to have partial positive charges, and this occurs on every single water molecule that exists here. Now the last example that we have of polar covalent bonds is ammonia whose chemical formula is NH₃, and once again you can see it has 1 nitrogen atom and 3 hydrogen atoms. The nitrogen atom is going to be much more electronegative than the hydrogen atoms which are not very electronegative. And so this means that the nitrogen atom is going to pull harder on the electrons.
There are different electronegativities once again. And so these electrons that are being shared here and here and here are going to spend more time with the nitrogen atom and that gives the nitrogen atom a partial negative charge. And once again, the hydrogens are going to have partial positive charges. And so, again, the main takeaway here is that polar covalent bonds are due to unequal sharing of electrons, and unequal sharing of electrons means that the distribution of electrons is going to be unequal as well which leads to partial charges. And so, over here on the far right, what we have is another image to help clear up this idea of polar covalent bonds.
So, basically, you can think in polar covalent bond because they are sharing electrons but they're sharing them unequally, there's pretty much a bully here in this tug of war battle on the electrons. And there's going to be one atom that is much more electronegative than another atom that does not pull very hard on electrons. So, the electron that's being shared is going to spend more time with the more electronegative atom and that creates a partial negative charge. And, the atom that is kind of deprived of the negatively charged electron becomes slightly positively charged, partially positively charged. And so, this all results from unequal sharing of this electron and that's why you can see that the electron is closer to the more electronegative atom because it pulls harder on it.
And so this here concludes our introduction to polar covalent bonds, and we'll be able to get some practice moving forward in our course. So, I'll see you all in our next video.