in this video we are going to go over a way that we can quickly distinguish a polar molecule from a non-polar molecule now it's easier if you know what to look for when a molecule is nonpolar and before you find out what to look for when it's polar the first category of non-polar molecules are those that are made up of one element for example if you have a monoatomic atom or a datomic atom that's completely posed of one element it's nonpolar examples include for example uh N2 that's a diatomic molecule um O2 cl2 um F2 H2 these are all non-polar and some of the monoatomic gases like helium neon argon Xenon the noble gases um those are also non-polar the next category to look for is um a molecule that contains only carbon and hydrogen those molecules are non-polar so for example methane um your alkanes uh ethane c2h6 eth ch2 double bond ch2 these are composed only of carbon and hydrogen and therefore they are non-polar the carbon hydrogen bond is nonpolar the third area to look for is if the molecule has symmetry so for example um carbon tetrafluoride notice that all of the outer elements are the same uh this molecule has symmetry this is non-polar um sulfur hexor not yeah sulfur hexabromide all of the outer elements are identical this molecule is also uh nonpolar carbon dioxide another nonpolar molecule the two outer elements the oxygen are the same uh phosphorus Tri chloride that's another non-polar molecule each of these molecules they have symmetry as you can see bh3 Boron trihydride also uh nonpolar now let's let's say if the molecule lacks symmetry is it always going to be polar well it all depends on the difference if the electro negativity difference if it's less than 0.5 then um it's going to be non-polar if it's more polar let me give you an example of that so iodine monob bromide iodine has an electro negativity value of 2.5 and for Bromine it's about 2.8 because the difference is like3 this bond is relatively non-polar another example if there's no symmetry is bromine monochloride chlorine has an electro negativity value of 3.0 and here once again thean difference is less than 0.5 so that molecule is non-polar so those are some quick ways that you can use to identify if molecules nonpolar if it doesn't meet those characteristics generally it's going to be polar so what are some quick ways to identify polar molecules the first thing is if you see um if a molecule has hydrogen bonding it's going to be polar so if hydrogen is directly attached to nitrogen oxygen or Florine it's polar examples include water um NH3 HF ch3 o even though the carbon hydrogen bond is nonpolar the presence of the alcohol means that you have hydrogen bonding and therefore it's going to be polar uh ch3 nh2 um because of the nh2 um it's polar ch3 Co once again because of the O It's polar now also if the molecule lacks Symmetry and if the bond is polar then it's going to be a polar molecule here's another example here the oxygens here these oxygen are identical and it has symmetry which makes it non-polar here this molecule um it does not have symmetry like uh this one did carbon has an electr negativity value of 2.5 oxygen is 3.5 so this bond is polar here for sulfur it's also 2.5 so that carbon sulfur bond is non-polar but because of the carbon oxygen Bond it's polar in the case on the right when we have carbon dioxide even though the carbon oxygen bond is polar because of two of them because of the Symmetry those dipole moments cancel out and therefore um CO2 is non-polar but if you replace one of the oxygen with a sulfur molecule then it becomes uh polar let's look at another example ch3 F notice that it's similar to um to this molecule right here the carbon Florine bond is very polar carbon has an electronegativity value of 2.5 and for Florine it's 4.0 it's well above that 0.5 difference and um so because of the carbon Florine Bond it's polar the carbon hyd hydrogen bond is relatively non-polar so the dipole moments are very small for that but in this case over here these diap moments they cancel and that's why because if you have symmetry it makes it non-polar but because this molecule lacks symmetry it's going to be polar another example is sulfur dioxide cuz sometimes the shape of the molecule can affect the polarity see carbon dioxide which looks very similar to sulfur dioxide and the fact that there's two oxygens and one atom in the middle um because carbon dioxide has a linear shape the diap moments they cancel but because sulfur dioxide has a vent shape the arrows the diap moment they don't cancel and you can see um because of the lone pair this molecule lacks symmetry so that also makes it polar the last example is if you look at NH3 even though it has has hydrogen bonding which makes it polar um the geometry also makes it polar as well if you draw the arrows they all Point towards the partially negative Florine atom and they point in One Direction they don't cancel and that's another reason why this molecule is polar so just to review molecules that are non-polar tend to be um diatomic um molecules that are composed of one element or monoatomic atoms like noble gases they could be pure hydrocarbons or they could be molecules that have symmetry where all of the outer elements are the same if you see that 99% of the time it's going to be non-polar if you don't see it for the most part it's probably going to be polar but just to be on a safe side um look at the electro negativity values if it's greater than 0.5 um draw the arrow from the partially positive atom to The partially negative atom and if the arrows don't cancel then your molecule is going to be polar so hopefully this uh video will help you to quickly distinguish polar non-polar molecules and uh I wish you well in your general chemistry course