so this tutorial is going to be about bond polarity and dipole moments so let's look at this question show the bond polarity and dipole moments in the following bonds and molecules so let's start with the carbon oxygen bond so how can we show the bond polarity and dipole moment and also how can we determine if that bond is going to be polar or nonpolar so what we have right now is a covalent bond carbon and oxygen are both nonmetals whenever you have two nonmetals combined typically a covalent bond is formed and to determine if it's polar or nonpolar we'll need to look at the electronegativity values if the en difference is less than 0.5 then what you have is a nonpolar bond if the electronegativity difference is greater than 0.5 then you have a polar covalent bond carbon has an electronegativity value of 2.5 and oxygen is 3.5 if you need access to these numbers i suggest that you go to google images and type in electronegativity values from the periodic table or something like that now going back to this we see that the electronegativity difference in this molecule is 3.5 minus 2.5 so that's 1.0 so therefore the carbon oxygen bond is a polar bond or a polar covalent bond now that we know that oxygen is more electronegative than carbon we can indicate the bond polarity oxygen has a partial negative charge and carbon has a partial positive charge now to draw the dipole moment you need to draw an arrow that starts from the positive part of the molecule and points towards the negative part of the molecule so this is the dipole moment and this represents the bond polarity now whenever you have a net dipole moment the molecule as a whole is polar if all the dipole moments cancel and then the molecule as a whole is nonpolar but we'll talk about that later let's move on to our second example the oxygen fluorine bond so go ahead and indicate the bond polarity and the dipole moments for this bond and determine if it's polar or nonpolar so let's look at the en values first oxygen has an electronegativity value of 3.5 and fluorine is 4.0 so the en difference is 0.5 which makes this a polar covalent bond both oxygen and fluorine are non-metals and whenever you have two nonmetals combined typically they form covalent bonds but we have a polar covalent bond because fluorine and oxygen they don't share the electrons equally fluorine is going to pull the electrons toward itself and because it's more electronegative it's going to acquire a partial negative charge whereas oxygen is going to be electron deficient it's going to have a partial positive charge so that's the bond polarity of the oxygen fluorine bond now the last thing that we have to draw is the dipole moment and just point the arrow to the element that is most electronegative in this case fluorine and so that's the dipole moment of the of bond now let's move on to part c the sulfur hydrogen bond sulfur is a nonmetal and hydrogen is a nominal so therefore this is going to be a covalent bond now is it going to be a polar covalent bond or a non-polar covalent bond by the way if we had a metal and a non-metal typically it would represent an ionic bond hydrogen has an electronegativity value of 2.1 and sulfur that is about 2.5 and so the electronegativity difference is 0.4 which means that the hydrogen sulfur bond is relatively nonpolar so what we have is a nonpolar covalent bond sulfur is more electronegative than hydrogen so sulfur is going to have the partial negative charge and hydrogen is going to bear the partial positive charge so to draw the diaper moment we're going to point the arrow towards the more electronegative sulfur atom and so that's it for that example so now what about molecules so here's how you draw water so that's a simple lewis structure of the h2o molecule so given this molecule with the appropriate geometry indicate the bond polarity and the dipole moment so first let's focus on the oxygen hydrogen bond oxygen is 3.5 and hydrogen has an en value 2.1 so oxygen bears the partial negative charge and hydrogen bears the partial positive charge so this bond is a polar covalent bond the electronegativity difference is 3.5 minus 2.1 that's 1.4 so it's much greater than 0.5 and the dipole moment of this bond is going to point towards the oxygen atom so the o h bond is polar now if we draw the dipole moments from the molecule it's going to point towards oxygen now to indicate the bond polarity we know that hydrogen is going to have a partial positive charge and there's two of them so oxygen needs a partial negative charge that's twice the value we got to put a 2 in front of it so we can neutralize these two partial positive charges so make sure you put that 2 in front and so that's how you can indicate the bond polarity and the dipole moment of a molecule so now we need to ask the final question is the molecule polar or nonpolar because you can have a molecule with polar bonds but overall the molecule itself may be nonpolar and so you need to look at the arrows the dipole moment so we have one arrow going this way and the other arrow going this way for the molecule as a whole to be polar you need to have a net a dipole moment based on the way this molecule is drawn notice that the x components of the arrows cancel so these two opposite in direction they cancel but the y components do not cancel they point in the same direction so therefore this molecule has a net dipole moment in a positive y direction so because there's a net dipole moment and these two arrows do not completely cancel we could say that the molecule as a whole is polar now let's consider methane ch4 methane has a tetrahedral structure so it's not easy to represent it on this screen because it's a three-dimensional object not a two-dimensional object now the carbon-hydrogen bond is non-polar the electronegativity difference is less than 0.5 in fact it's 0.4 however carbon stills bears the negative charge and hydrogen bears the partial positive charge so to indicate the bond polarity of methane we need to show the four partial positive charge of every hydrogen atom for carbon it's going to have a negative charge but we're going to multiply by four due to these four charges so that's the bond polarity of the molecule now the dipole moment is going to point towards the electronegative carbon atom so we have one going here they go in there and if you draw this molecule it's 3d structure and you look at the arrows correctly or if you really analyze it the way this structure is set up it's set up in such a way that all of the dipole moments completely cancel each other so that the net dipole moment is zero so what we have is a molecule that contains non-polar bonds and at the same time the molecule as a whole is nonpolar overall now let's look at our last example carbon dioxide so i'm going to give you the lewis structure of this molecule it looks like this so go ahead and work on that problem the electronegativity difference between these two atoms is 1.0 so what we have is a polar covalent bond carbon is partially positive with respect to oxygen because oxygen is more electronegative than carbon and so the dipole moment is going to point towards the electronegative oxygen atom so this is going to be partially negative and carbon is partially positive times two so now we have a diaper moment that points towards the oxygen atom and because there's two bonds we're going to have two arrows now notice that these arrows are opposite in direction which means that they completely cancel out so the dipole moment for this entire molecule is zero so even though the carbon oxygen bond is polar the carbon dioxide molecule is nonpolar so this is one example where you can have a molecule with polar bonds but the whole molecule is non-polar overall due to the fact that there is no net dipole moment you