hello and uh welcome back to part three of our look at chapter two uh dealing with biochemistry at the end of the second video we left off looking at and talking about ionic bonds and their role in creating something that we refer to as electrolytes and in this third video we are going to be more focused on another type of bonding called covalent bonding and what is important to remember about covalent bonding is that it is not a joining of two atoms through a given take of electrons but it is a joining of two atoms that involve a sharing of electrons so if we go back to my example of ionic bonding where maybe you your pen runs out of ink and you raise your hand and you go hey young i need to borrow a pen and so i walk over and i i let you use my pen but the the catch this time the catch this time is that you get to use the pen for two minutes and you can write whatever you want you can do whatever you want with that pen for two minutes but then i get to borrow the pen and use the pen for two minutes and i can do whatever i want with the pen for two minutes and then you get the pen for another two minutes and then i get the pen for two minutes and so there's an equal sharing of the pen well if the pen is the electrons it is a equal sharing it is an equal sharing of the electrons right so the electron spends equal time with the with both atoms that are involved with the bonding and that's exactly what you are seeing right here all right so we have two hydrogen bonds all right these are both um nonmetals right these are both nonmetals uh hydrogen here has one electron it wants one more hydrogen here has one electron it wants one more and so how how it arranges that is it says all right between the both of us we have two electrons and these two electrons are going to spend some time orbiting over here and they're going to spend some time orbiting over here and then come back over here and then back over here and so it is a sharing of electrons now depending on the element sometimes that element has to form multiple covalent bonds with multiple atoms in order to acquire a full valance shell of all participants well what do i mean by that well hydrogen atoms they they form a single bond right they're going to share one pair of electrons and that gives them a full balance energy shell but things like oxygen oxygen has to form two covalent bonds they have to share two pairs of electrons why is that well it is that way because if you remember oxygen has an atomic number of eight which means it also has eight electrons all right so oxygen is going to have two electrons on that first shell and then on the second shell it's going to have one two three four five six right it's missing two electrons and so how does it compensate for that well it compensates for that by maybe forming a covalent bond with another oxygen this oxygen is going to have one two three four five six electrons on its outer shell two on the inner and so if these two electrons are shared and these two electrons are shared we now have one two three four five six seven eight electrons for over here and we have one two three four five six seven eight electrons circling over here right so now they form two double bonds right this is what we call diatomic oxygen or atmospheric oxygen nitrogen for example nitrogen can form three bonds why because they have two on the first all right and uh five on the third energy shell for a total of seven electrons well i'm sorry for yeah for a total of seven right two on the first five on the second well it wants another three and so it can form bonds and so if we look at nitrogen for example here's nitrogen one two but it has a total of seven so we need one two three four and five well what can nitrogen do in order to covalently bond and create eight electrons well what it can do is it can actually bond with hydrogen which has one electron and it can bind with hydrogen which has one electron and it can bond with hydrogen which has one electron it's sharing one pair here another pair there and another pair there one two three four five six seven eight this valance shell is now full and look at what hydrogen does hydrogen has one it's going to share that one hydrogen has one it's going to share that one and so both of these elements get something out of it this is what we call ammonia or ammonium right nh3 carbon carbon can form four bonds up to four bonds why because it has an atomic number of six and so carbon has one two one two three and four holy poop it can make up the four bonds and here's the amazing thing carbon can form all single bonds with hydrogen ch4 that's what we call methane or it can form two double bonds with oxygen creates co2 carbon dioxide or or it can go ahead and create a triple bond and a single bond what it cannot do is form a quadruple bond but think about this carbon has the ability to form single double and triple bonds it can form one double bond and two single bonds it can do four single bonds it can do a triple and a single it can do two double bonds there is a lot of diversity that is built in there's a lot of diversity that is built in carbon because it has up to four available spaces to engage in covalent bonds and so that's exactly what you are seeing right here here's carbon hydrogen hydrogen hydrogen hydrogen that's what i just got done drawing on the previous page you've got four single bonds that are created again oxygen can create two double bonds here's one bond here's the second bond all right nitrogen can do three single bonds or what we call a triple bond here's one here's two and here's three the difference here is with with an ionic bond you've got a non-metal that's joining with a metal through the formation of ions because remember one atom is giving away one or more electrons and the other atom is accepting more than one one or more electrons it's not an equal sharing of that electron it is a giving and taking but with covalent bonds with covalent bonds there is equal sharing there is equal sharing in this case i'm going to give you an example where there is not equal sharing coming up here but i want you to i want that to sink into i want you to sink into this all right carbon has a lot of flexibility in what it can do it can it can connect with hydrogen it can connect with oxygen it can connect with phosphorus they can connect with nitrogen it can it can connect with any other non-metal that it wants to any other non-metal it wants to it can form double triple and single bonds with any other nonmetal that makes it versatile that makes it very versatile and you're going to see that time and time again as we start to get into the macro molecules so don't let that thought get lost i i want you to appreciate the complexity that carbon brings to biochemistry so um i just got done mentioning that sometimes covalent bonds are not engaged in equal sharing but instead unequal sharing of an electron in the case of an unequal sharing of an electron what we see happening is one atom is monopolizing the electrons more than another atom or other atoms could be more than one atom so one atom is getting more time with the electrons and the other atom or atoms are getting less time with the electrons and when we do that we create unequal sharing we create what we call a polar covalent molecule you can rightfully so add in the term right here you can add in the word polar covalent molecules because it is still a covalent bond there is still a sharing of electrons but that sharing is not equally split it's kind of like fighting over a child between two diverse or between two divorced parents one parent maybe both parents get to get the child or the children two weekends a month great that's a covalent bond it's a regular covalent bond 50 50 equal sharing but maybe one parent gets the children three weekends a month and the other parent gets the children or the child one weekend a month they're both sharing the child or the children but they're not sharing the child or children equally and that's what's happening with our atoms they're not sharing the electrons equally and because of that the electrons spend more time with one atom which gives that atom a partial negative charge because the electrons spend more time with it and because the electrons are spending more time with one atom the other atoms have a partial positive charge because they have the children less they have the electrons less right it's not equal sharing take water for example all right h2o h 2 o there's our there's a there's our water molecule right there's our water molecule oxygen is larger than the two hydrogens oxygen has more protons than what water does oxygen has eight protons hydrogen has one proton hydrogen has one proton and we talked about the fact that opposites attract we've talked about this idea that opposites attract well are you ladies i'm going to pick on you for a second are you more attracted i need you to let me preference this i need you to put your shallow self-serving greedy persona on all right you're only looking out for yourself and you're going to be very shallow no depth to this we don't care about how charming they are we don't care how sweet they are we don't care how good they look in mark anthony clothes we don't care all right you've got a choice between two guys one guy is packing eight figures he's a millionaire he's a millionaire right the other guy is a thousand there he's he's just got a thousand he's just got a thousand but the other guy he's got millions tens of millions if we're going to stick with eight an eight figure bank account as opposed to a four figure bank account who are you going with now this is your shallow self this is your self-serving and your greedy self and damn right you're gonna go with that ten uh the person that has 10 20 30 million dollars you're gonna go with the eight figure guy there's a tick tock in there someplace i ain't going there though you're gonna go with the eight figure guy the electrons are the shallow females in the class usually this is where i have you guys raise your hand in class and identify yourself so that way the guys know who to stay out stay away from can't do that here just like you're gonna go with the eight figure guy the electrons are going to go with the atom that has eight protons because there's more positivity there there's more attraction there it's what we call electronegativity where the electrons are going to be attracted to the more positively charged nucleus and so because oxygen has these eight protons the electrons spend more time here which means they have 10 electrons here because this one and this one is going here 10 electrons versus 8 protons you get yourself a partial positive it's partial positive because it's not always i'm sorry partial negative it's partial negative because those electrons are not always with oxygen sometimes those electrons are going to go with the poor literally the poor hydrogen ions with its one proton as the electron moves further away from the nucleus of the oxygen it loses its power it loses its attraction and hydrogen can go and suck it in and it can spend some time with hydrogen but because the majority of the time the the electron is not with hydrogen it's got more protons than electrons and so therefore it's a partial positive charge and so you can see when we have equal sharing of electrons you get this nice linear delineation of a covalent molecule that's what you see with carbon dioxide but when we engage in polar covalent bonding there's very often a bending effect to the molecule because of the formation of a slightly positive and slightly negative charge now this gets a little bit deeper because water has a slightly positive and a slightly negative end to it which makes it ideal for being a solvent it is why it is y ionic compounds dissolve in water because the partial negative end of the molecule in this case the oxygen can be attracted to the positive ion the cation within the ionic molecule the sodium and the partial positive end of water the hydrogens can become attracted to the anion of the ionic bonded molecule the chlorine and when the water arranges itself around the sodium and the chlorine their respective attractedness pulls apart the ionic bond so that you end up with an electrolyte you end up with sodium ions and chloride ions what happens when you remove the water weapons when the water evaporates out salt crystals reform the sodium ions and the chloride ions re-attach they join back together again all right and so this table here just kind of gives you a visual representation between the three types of bonding that we have discussed an ionic bond a polar covalent bond and a non-polar covalent bond or what i identified as being just a regular normal covalent bond this is a good summary table for you to pay attention to and then the last slide that we're going to look at here today right and that is a hydrogen bond now a hydrogen bond is a special covalent bond and it is a hydrogen bond that does not hold together atoms but instead a hydrogen bond links two molecules together so water has this partial positive in this partial negative end guess what the partial negative end of one water molecule the oxygen becomes slightly attracted to the partial positive end of another water molecule the hydrogen because opposites attract and the bond that re that that is created from this attraction between the partially negative oxygen molecule of one water molecule and the partially positive hydrogen atom of another water molecule is called a hydrogen bond it's weak it's a weak covalent bond because of the partiality of the charge sometimes that hydrogen is going to have its electrons it's not going to be partially positive anymore sometimes that oxygen is not going to have those extra electrons and so it's not going to be partially negative and this is what allows water to stick to itself this is what allows water to cling to other surfaces this is what allows water to freeze to be a liquid to be a gas this is what allows surface tension to exist this is what allows for polarity for being a solvent all of that is predicated within these hydrogen bonds it's not a sharing of these electrons and it's not a giving and taking of these electrons but it is an attraction based on partial negative and partial positive charges that creates this special category of covalent bond that we define as being a hydrogen bond and we're going to talk more about these guys as we start going through some of the other biomolecules in video five starting in video five and so with that note or i should say on that note i am going to let you kind of digest this this was a little bit more of a we're starting to build on this information so we kind of did some review with ionic bonding and we kind of took the basic principles of that and applied it to this notion of a covalent bond or polar covalent bond and its relationship of an ionic bond and a hydrogen bond in the form or i'm sorry an ionic bond and a covalent bond and the characteristics associated with a hydrogen bond so uh with that uh keep studying keep reviewing keep jotting down some information and uh you know what you you know what i'm gonna say i'll catch you on the flip side