okay so this lesson is about the different types of chemical bonds the difference between ionic bond and covalent bond and also polarity all right so we're gonna basically review grade eleven concepts here and we have to start with electronegativity because chemical bonds and on your electronegativity so what is electronegativity so this is perhaps one of the most important concepts in chemistry because it explains so many things about our natural world with behavior of different compounds so the electronegativity simply is the tendency of an atom to attract neighboring electrons so how good you are at attracting electrons well that is just your electronegativity so an analogy would be well handsomeness the tendency of a male to attract a female so Justin Bieber would be an example of a handsome individual he has a lot of fans and a lot of manuals would just flock to is Justin Bieber so if Justin Bieber was an element then he would have high electronegativity so different elements have different electronegativities some of them are similar but generally they're different and there is a trend on the periodic table that describes electronegativity so as you can see in the top right corner you have fluorine that will be the Justin Bieber of the periodic table bottom left you have the ugliest element francium the lowest electronegativity so the trend is when you go to the right and up electronegativity increases or as it goes to the left and down electronegativity will decrease okay the reason for that well we've learned that in grade 11 honestly not all that important agree 12 you just need to know what this is and how to look for it on the periodic table so the important part about electronegativity is we need to look at the difference in electronegativity between two bonded excellence okay now when there is a difference electronegativity that determines the ionic or covalent characters of that point and to find the difference all you have to do to subtract them and you can look up the values of each elements their electronegativity on the periodic table so I have a video explaining some periodic trends and electronegativity alright so that was a summary on periodic trends and just review of electronegativity like I said that the types of bond that you have ionic or covalent it depends on the electronegativities of the two bonding accidents and this picture summarizes that pattern and you can see that instead of being black and white in being binary either ionic or covalent it's actually a spectrum alright it comes in bodacious if you have a large difference in your delta e and the difference in electronegativity that means you have more ionic character in that bog and if your difference in electronegativity is relatively small then that means you have more covalent characters in your blog all right so it's not a black and white thing it's not like you flip the switch you go from covalent ionic okay so there are things in the middle that I have both ionic and covalent characters so as you progress from one end to the other you increase your honor character will increase your covalent character and in this diagram you can see what the magic number are if you see look at the thing on the bottom one point seven that's the cutoff for being an ionic bond okay if the electronegativity between two elements is greater than 1.7 you would be considered to be ionic and if it's less than that you will be considered to be covalent and still with covalent bonds you have two different types you can have polar or nonpolar covalent bonds and if you have a nonpolar covalent bond it simply means that the electrons are shared equally okay everybody gets the same amount of electrons for the same amount of time and if the difference is large that means between 0.4 and 1.7 then you have unequal sharing of the electron so despite the fact that they're sharing they're not sharing equally so one atom has the advantage they have the electrons closer to them for longer periods of time so still sharing but polar covalent all right so let's summarize this again so if you have an ionic bond the difference has to be great enough that it exceeds 1.7 now if this were to occur the attraction of those electrons from one atom will greatly exceed the other atom so as a result those electrons will be stolen by the atom with the higher electronegativity alright so this is not sharing any more if you straight-up steal the electrons you can't call the sharing so that would be ionic and not covalent does that make sense oh this has to do is with the force of attraction in other words electronegativity okay high electronegativity you have a higher tendency to attract electrons so you better at attracting so electrons are closer to you and this is also not important now if you have a covalent bond that means no one is winning so no one takes those electrons so the difference in the electronegativity is smaller there's still a difference okay but that difference is not enough one of the size to win this tug-of-war and a great and we teach covalent bonds like you know it's sharing and caring like how atoms are sweet y'all you need an electron up here you can have my let's share it's not like that okay what they're really trying to do is take the electron from each other it's just that they're not strong enough to do that so they're kind of stuck in this type of work so that's the covalent bond so nobody's strong enough to completely steal the atom so they compromised and the electrons gets shared between the two atoms so this is covalent bonds alright so any questions about this so far all right there are two types of covalent bonds you can have a polar covalent bond and a non polar covalent bond so let's look at the polar one first what do you mean by polar well if the electronegativity difference is between 0.5 and 1.7 so it there is a clear difference between the two but that difference is not so big that one of them dominates the other then you have a polar covalent bar so the electrons are shared but this is unequal sharing and the electron is actually closer to one atom over the other okay and the higher electronegativity will obviously have the electrons closer to them and as a result you have Delta negative on the more electronegative atom and Delta positive on the more electropositive so now there exists a tiny difference in their overall net charge the overall molecule is still neutral but the distribution of that charge is different it's not uniform okay does that make sense okay now what do I mean by Delta negative if your Delta negative that means you are partially negative it is not a full one minus if you are a full one minus time you completely stole that electron you become one - but you did it you still sharing you have that electron most of the time but you have to return that electron to the other atom sometimes so you don't get the full benefit of the negative charge so that charge is technically between negative one and zero you're still negative it's just that you're not fully named likewise with the positive charge if you have Delta positive you are not having those electrons most of the time so as a result you're more positive than you should be so but still you didn't lose that electron entirely that electron still comes back some time so you don't have a full one plus it's between zero and one plus they have a partial positive charge all right does that make any sense so we're talking about partial charges that can result from unequal sharing of electrons so that's a polar covalent bond the other type of covalent bond will be a nonpolar covalent bond this simply means the electrons are shared relatively equally if you have similar electronegativity and by similar I mean the difference is less than 0.5 you can even have a difference of 0 I mean they're completely equal now if there's nothing about no problem as long as it's less than 0.5 the difference is too small okay to make any significant to have a significant effect so effectively they are equally shared between the two atoms and they are found exactly in the middle between them so you don't have any partial charges the charge is uniformly distributed amongst the entire molecule you will have a nonpolar covalent bond all right so that's the difference between polar versus nonpolar so sharing is not simply sharing there are different ways to share so here is a summary of all of them again you can have nonpolar which is the equal sharing of electrons between two atoms you can have polar covalent that means the unequal sharing of electrons between two atoms and finally ionic the complete transfer of one electron to and again the numbers you need to know it is polar if the electronegativity difference is between 0.5 and 1.7 nonpolar if it's less than point five and I on it if it exceeds one point seven all right so do we have any questions so far okay no where did these numbers come from is 1.7 a magic number it has any significance that we use 1.7 or is it just an arbitrary number that we have to choose in order to draw a line well the answer is latter we have to draw lines somewhere if you want to talk about ionic versus covalent bonds well you have to have a definition right so that means you have to pick an arbitrary value somewhere along the spectrum and decide that hey here's my mind if you're greater than this number you gotta be I on it if you're less than that number you've got to be prevailing okay so that makes it convenient for us for semantic reasons there's nothing special about that one point seven that's where we decided to draw that line this is akin to at what age do you become an adult the law says 18 okay if if the clock strikes 12 on your 18th birthday you officially become an adult and you unlock some new skills okay some new privileges but does it really make a difference biologically is there really a biological or psychological difference between a 17 are all in 18 year old probably not okay nothing magical happens to you on your 18th birthday you're still you you wouldn't see any difference in the mirror you wouldn't have a change of mind you're not gonna have an epiphany you're still used it's just that the law changes for you because we decided we were we we gotta draw the line somewhere how do you determine know what a kid is and one of the thought is well less at 18 different cultures different time periods they pick a different age think in the past 16 was the age with like drinking alcohol for example 19 and some provinces 21 in the United States what I mean so this is completely arbitrary because we want to define something we have to draw a line so just keep in mind this is a gradual continuous spectrum okay if you have electronegativity difference of exactly 1.7 well that's our theory but you can call this ionic but some people can say well this is this is really covalent but you don't strongly ionic characters so again it's murky same thing with the point five it's just an arbitrary place we have to draw the line okay what is significant difference what is not just an everything difference okay if I pluck one hair from your head I don't think you would mind if I pluck - I don't think you would mind you notified about 20 I don't know if I plug 100 you probably will get piston you don't do something about that so what is that line what is the significant difference we just got to pick a number and we picked one five so I'm saying this just to remind you that this is a spectrum life is not black and white see covalent ionic is not binary it's actually a spectrum who wanted to be mind raised for our own and benefits to make it simpler so let's do some example questions determine whether each of these bonds are ionic polar covalent or nonpolar covalent so let's do them together if you don't have a periodic table open I suggest you find one because that's where you will find the electronegativity difference Walter you electronegativity balance it starting with the first one see at home Carmen has an electronegativity of two point six oxygen is three point four if you do the math you get the zero point eight what is it anyone well there could be one that would be polar covalent okay point eight is greater than point five but less than one contaminant so it's quite clearly polar covalency how this works if you have fluorine and I ding I don't remember the electronegativity difference between those Florina for I think I don't know if you just look on the periodic table you should see is 2.7 and you take the difference the difference is 1.8 sorry 1.3 so this is again polar covalent alright see you see how this works what about the next one LIF well flooring is for you know that I but what about lithium anybody or minus one okay and that's a three so this is a whopping three difference between the two electronegativities and you only have to be a difference of 1.7 or greater so obviously this is ionic now you might be thinking does the grade 10 definition still work right look lithium and fluorine metal nonmetal that's ionic that's what you learned in grade 10 carbon oxygen like fluorine I mean those are all nonmetals phenomena nominal is a covalent bond that's what I learned in grade 10 so that still works doesn't it can I just take a shortcut I just do the definition is that because I really don't want to look up the periodic table I don't want to look I don't want to do the math well you'll see the answer to that over the next two examples a germanium and ten if you want to use the grade 10 definition while germanium I believe that's a metalloid it's not a metal tin is definitely a metal so basically you have two metals happy two metals bond like we never talked about two metals bonding before so is that impossible well yeah what type of bond is this according to our new definition if you just look them up to help you know that's situate to the right VP block your boobs - yeah they're both - they're exactly the same right so that means they have was your difference so that would be nonpolar covalent here is where your mind gets blown away what you might also have a covalent bond what well the next one should mess you up even more aluminum and chlorine the electronegativity difference please one point six so chlorine is 3/4 - aluminum is 1.6 the difference is 1.6 1.6 by definition means it is polar covalent bond because it's less than 1.7 you see if you were in grade 10 you asked this question to a grade 10 student it's aluminum chlorine a covalent bond or ionic they're gonna say ionic because it's metal and nonmetal aluminum to metal forming two non metal itself by definition that is ionic but in grade 12 we actually reverse that answer and we say it's covalent now again this is all semantics because if you have a difference of one point six that's like arguing you're 17 years old you murder somebody should we put you in prison or should we put you in juvie hall my law is juvie hall like 17 are you really that ignorant and not know the consequences of killing somebody not when you know what you're doing according to law you're not an adult yeah you see what I mean so if you really want to play by the rules it is called a covalent but if you want to make an argument that this is ionic I mean who's here to tell you you're wrong so we have to pick a right answer no you can't have an argument so we say that this is polar covalent with the high ionic character so we recognize that this is really close to an ionic bond but you know we still have to draw the line so sorry that's climatic okay so if you draw the Lewis diagram of this I've seen both I've seen the ionic version you just put it in square brackets and three chlorines l3 and I've seen covalent structures where aluminium makes three covalent bonds with the chloride and aluminum only needs to Rico available it is one of those exceptions it is exactly the same as boron boron only needs six with its electrons that's a special one aluminium same things for the same reason okay so you can argue that aluminium also makes Coby in the bonds so that actually blows our mind a little bit covalent bonds are no longer restricted to non metals metals can do it in fact a lot of the transition metals they have intermediate electronegative really right so that means they are able to make covalent bonds so this makes sure that you use our new definition now not the metal nonmetal definition anymore all right so if you are polar okay you would have a dipole or a dipole moment now what is a dipole moment the definition of the dipole moment is a partial separation of charge what does that mean the plain English it means that you have partial charges partial positive and partial negatives and they are separated in the same molecule so a dipole we used usually use our word for a magnet magnets have dipoles the North Pole and the South Pole the earth is a giant magnet the earth has a North Pole and a South Pole now in polar molecules it is like a magnet it has a positive end and a negative end just like a magnet while magnet has north itself but opposites attract and like repel the same thing so you can view this as a giant or actually a tiny magnet in this picture the hydrogen is partially positive because fluorine is so boxy it has an electronegativity difference of 4 so it's gonna take those electrons and put them really close to itself so hydrogen as a result becomes partially positive fluorine is partially negative and this generates a dipole moment and we represent a dipole moment using an arrow the arrow should point from the positive end towards the negative end at the positive and we use a plus sign for the end of that error the tail of the arrow is a plus sign just to remind you that this is the positive end all right so now make sense so a dipole exists in a polar molecule with polar bonds if you have a polar bond you will have a dipole pointing to Lourdes the negative now it is worthwhile to notes before I move on because I forgot to mention earlier HS because we are looking at H F right now you might think that is ionic according to our definition because for - to put you is 1.8 which exceeds one consignment so ionic right well actually no that's what we break the rule it is still polar covalent because they are still shared so yeah that that system is flawed it's just a rule of thumb for us to know make a decision easier like I said if you're 19 years old well I don't good kid to say so yeah just keep him on H F it's still polar covalent now we mentioned that bonds can be polar or nonpolar but we didn't say anything about the entire molecule of being polar or nonpolar takes the bonds have polarity but so do entire molecules so if you look at the picture here HCl is being Chun of the green represents chlorine the hydrogen for the colors Co is polar because chlorine is more negative the country and HCl be a gas they will move in a random direction and they will be fixing in American direction that you're just moving around so no organized pattern however if you place them between two plates of all of the charges you will have an electric field that points in one direction and if you put HCL in an electric field the negative chlorine because it's partially negative it will point towards the positive plate and the positive hydrogen will point towards the negative plate it will become aligned with the electric field because the molecule itself is polar all right so molecules can be polar not just their bonds so we've learned that next there's a difference between on hole in a polar molecules we're talking about in time molecules not so how do you tell whether a molecule is polar or not well there are two questions that you ask okay and a molecule will be non-polar if it satisfies just one of these two conditions so what are the conditions well the first condition it is symmetrical as long as you satisfy one you are nonpolar so if you're symmetrical congratulations are nonpolar you don't even care about what the other condition is well let's just look at the other condition the other condition is you have a low electronegativity difference if the Delta en is less than 0.5 that means your dipole is very weak and it is so weak it doesn't really make you real different so we just say you're a nonpolar anyway so looking at the three molecules on the bottom ch4 well ch4 has a strength electronegativity difference okay the difference is very small but carbon is slightly more negative than hydrogen that that difference is very low with that alone we say you're not polar okay but let's say that difference is not small even if the difference is big you're still nonpolar because you are symmetric so that happens to satisfy both conditions you don't need to satisfy both conditions but you get but the second one a bf3 boron has low electronegativity fluorine has the highest electronegativity so the difference between fluorine and boron is huge all right so fluorines are very negative that boron in the middle is very positive so you have a large difference you don't satisfy condition number two but you're still nonpolar why because it's satisfied condition number one it is symmetrical okay it is evenly distributed in all ways in all directions if you learn physics imagine them as forces force vectors okay imagine like there's a car in the middle you have wheat donkeys pulling on that cart in those directions well all the forces will cancel out exactly you have put next to zero force and the cart doesn't move and I see how this works so given that it is symmetric you still say that bf3 is nonpolar same thing with the next one sf6 all the force vectors will cancel out there all point in opposite directions of the next dipole it is zero despite having polar bonds you have a non-polar molecule but did I make myself clear all right so molecules could be nonpolar despite having polar bonds to symmetry now the formula how do you know something symmetric right sometimes is not that obvious is something is symmetric here is a rule of thumb I'm going to use the bf3 that's an example how do you know that's metrics well it looks a metric but is there like a systematic way to determine whether something is symmetric well yes if you have a flat diagram instead of of expert I agree because you might get a Lewis diagram I sort of expert you can still do it something is symmetric if you are able to draw two lines of symmetry yeah needs to - I mean you can draw a line of symmetry like this I'm gonna draw here okay I just drew a line of symmetry the molecule is symmetric on that line you can reflect it back and forth it's gonna be the same thing but if you can draw two or more you are symmetric so let me just draw another one look I just drew another one that's another line of symmetry in fact I could draw a third one with the third bar but you only need two to be classified as symmetric in case and you aren't able to draw to you so congratulations with symmetric if you could just draw a one than your not symmetric okay so let's move on to polar molecules to show you what I mean all right so in order for something to be polar you have to satisfy both of these conditions all right so this is different from previously previously you just have to satisfy one so let me just go back real quick these conditions for nonpolar we call them sufficient conditions okay that means just having one of them is sufficient that's a sufficient condition to be nonpolar but for polarity these conditions are necessary conditions the difference is you meet them but doesn't mean it's enough it's like food is necessary for survival but it's food sufficient for survival no you need water as well you need warmth you see what I mean but food is necessary it's not sufficient so these modes these conditions are necessary that means you need to satisfy all of them so number one it has to be asymmetrical you can't be symmetric okay if you're not symmetric good you satisfy this condition not only that you also have to have a large electronegativity difference in other words there must exist a net dipole in there somewhere only if you check both of these boxes congratulations are polar if you check one of these boxes that's not enough it's like you go to the airport you want to fly to another country you need a passport and you need a plane ticket if you just have one and not the other you're not getting on a plane back there you need both so let's look at water water has Delta negative on the oxygen because oxygen is way more negative than the hydrogen okay if you draw the two dipoles they should both point from the hydrogen to the oxygens making a little triangle thing and again a recall vector addition the net dipole is the sum of those two vectors and if you want to add two vectors you have to add up their horizontal and vertical components their horizontal components cancel out that's a zero vector their vertical components they add up so the net dipole points upwards in red you have the net dipole moment so that means we're not symmetric you have a net dipole it means in polar the oxygen side is more negative than the hydrogen side all right summing sides for ammonia same story nitrogen is more negative than the hydrogen see so nitrogen bears a partial negative the hydrogen's all have a partial positive but it's the whole thing polar yes if you check out those three dipole moment vectors they all point towards nitrogen like a little pyramid the horizontal components all cancel but the vertical components they add up so the net dipole moment still points up all right so you do have a non zero net dipole you're also polar so how do you determine something is symmetric or not if you have a Lewis diagram well that water is a Lewis diagram if you can just draw one line of symmetry right there I just drew a line of symmetry down the middle if you flip back and forth it's the same thing I'm unable to draw another one there's no way for me to draw another line of symmetry I can only draw one then you're asymmetrical does that make sense so to be symmetric you know you must be able to draw two lines of symmetry alright so I hope I made myself clear on how to this city without distinguish between polar versus non polar molecules this is vitally important for you to know because polar molecules and nonpolar molecules have drastically different properties and behavior and if you can get those to know clear then you're gonna get a lot of questions wrong alright so let me show you another example carbon dioxide is supposed to be a non-polar molecule but it has polar bonds ok the carbon is Delta plus the oxygens are Delta minus because oxygen is more negative than hug of the carbon so you have two dipole moments one points to the oxidant the other one points right so you do have polar bonds none of those bonds are nonpolar they're all polar but the entire molecule is nonpolar because they cancel out you have a net dipole moment of zero whereas for water they add up they don't cancel out you see what I mean so you have to have a symmetry and an electronegativity difference all right so let's do example two together just to practice the first one top left cornor HCL polaron up over all right so each see a polar or nonpolar that will be polar okay because chlorine is more negative than the hydrogen okay so that's both ammonia on the right side oh we did that one already but it came with picture polar nonpolar oh right again they all point towards the nitrogen but notice that this is not flat if it was flat they would be not all about this all goes up so that is oh the middle one ccl4 nonpolar oh you know in Poland because everybody cancels out you see how this works there are four dipole moments and they all go in opposite directions and if you're something in the middle and there are four things pulling you in those directions you will not move so nonpolar bf3 no non-polar okay that's correct because they all pull in a direction since that they all cancel out okay if you do the math if you do the vector sum you should get and see what vector and lastly carbon with one chlorine but three hydrogen is what is that that would be polar of the geometry does look like it's symmetric but chlorine has more electronegativity than the hydrogen so it's not symmetric so that would be polar okay so is it clear which molecules are polar which monitors are not our on this the picture just didn't come with it it should have the arrows on them it's relatively easy to do it's questions like this if you have the diagram already you can just look at the diagram and decide whether it is or not but if you don't have the diagrams you have the chemical formula and if you happen to draw the Lewis diagram wrong that's what I stressed bond angles for the Lewis diagrams are important if you screw that up you're gonna get the wrong polarity they're gonna get the question wrong so please practice this I will take this up in seven eight minutes alright so go ahead and work on this draw the diagram and tell me whether it is polar or not okay so you have to first draw the Lewis diagrams and then determine the polarity so the first one HBR it's quite simple you just do are something like this you only have two atoms they must be connected and six nonbonding electrons for the bromine so it is polar or nonpolar that will be polar okay I don't remember what the electronegativity of bromine is but no definitely have a huge difference from hydrogen so that is polar because it's asymmetric and it has a difference in electronegativity so the next one nitrogen will be a polar or nonpolar so this is a really silly question because it has one single element so obviously you're gonna have the same electronegativity different so you're gonna be non-polar always now the next one contributor love is a polar or nonpolar that would be polar if you said polar then you didn't fall for the trap the diagram looks like this many will be tempted to draw a straight line for the Lewis diagram so I'm gonna draw the wrong diagram right here you might want to drop this okay I just want to say that this is incorrect if you draw something like that then you see oh wait it's linear so all the dipoles cancels and so that means it's nonpolar right well if you draw like that then you're gonna realize wait it's not symmetric so it's polar but there's another issue with that answer that issue is the electronegativity between the sulfur and the hydrogen is quite small if you look it up I think it's point four is that right yeah yeah I initially thought this was Ola until somebody pointed out wait but the difference is too small the aw crap I didn't even check though actually its non-core because the difference is just point four but then again you can make that argument well point four it is kind of on the fence right so it is nonpolar but kind of polar you see what I mean it is not significant but no it's almost getting there so by definition it is nonpolar so let's follow the definition here so I'm going to argue that this is non hauler of those if you want to say that polar but that's not what the definition says okay so next c2h6 what is it followed on power that will be nonpolar okay why is it nonpolar well first of all you draw the Lewis diagram and looks like that you have to know that this is this is not the accurate diagram this is not what the 3d one should look like they don't have any 90-degree angles despite what the diagram I suggest but a Lewis diagram despite being inaccurate and the bond angles it can still tell you whether it's color or not this is symmetric okay you can draw two lines of symmetries and you can see that that's a symmetric and because you have carbon hydrogen they have a small difference to begin with so this is non-polar and this fact is important because later on you're gonna learn organic chemistry and you're gonna learn about hydrocarbons so basically long chains of just carbon and hydrogen and they're all nonpolar because of this pieces they're a symmetric and B the difference is simply too small in their electronegativity so gasoline being a hydrocarbon is nonpolar C 2 CL 4 what is that one polar why am I getting two answers if you actually blow it up it's nonpolar because it's perfectly symmetric you can draw two lines of symmetries here and the bond angles are all 120 degrees despite that there is a difference between the chlorine and carbon and their electronegativity the symmetry you cancel that out okay so you're going home put the carbons in like a flat line or do I need to make them diagonal what do you mean by a flat line like yours are like on me to be fair I downloaded this picture from these pictures from the internet why did I choose these molecules in particular because I was able to find consistent artistic styles for these Lewis diagrams wanted to make it aesthetic not because I wanted to choose them because I found pictures of them so yeah I did in depicting the drawing this angle it doesn't it last on page three I hope you realize it looks like that polar nonpolar polar why do I say smaller oh if there's not oh yeah it's except the nonpolar didn't erect it is nonpolar it looks fuller because ammonia has the same structure and it's the peak of an end and that's polar so it is asymmetric okay but phosphorus and hydrogen have I believe the same electronegativity it's not only a difference point one insignificant okay so that's why it's nonpolar all right so I hope this exercise make you understand polarity a little bit better do we have any questions no all right the next part is a video so I'm gonna show you a video that summarizes bonding alright so this is the end of this lesson so we talked about electronegativity and how that affects on it which is covalent how did determine whether a molecule is polar and what a dipole is so do we have any questions before we go we don't okay all right so I'm gonna end the video here