hi guys welcome to the chapter on chemistry specifically the chemistry of life the beginning of the chapter will always again start with objectives I'm not going to read them all to you but these are things that you should be able to do by the end of the lecture you can use these to guide until you get the study guide so we'll start our discussion of chemistry with some basic terms beginning with matter matter is everything around us anything that takes up space or has mass no matter how small that mass is is matter so I am matter you are matter the computer the air around us the water we drink food we eat this desk everything is made up of matter now matter is made of tiny tiny little structures called atoms okay billions of atoms make up each cell an atom is the smallest stable unit of matter now when we use the term atom we could say one atom of hydrogen one atom of carbon one atom of oxygen what that means is that it's one single unit of oxygen atoms are tiny right much smaller than you could see you know even with a microscope they're very very small but they joined together to create everything right to create you and me so they they must be able to join together to make larger things and it's interesting because when atoms joined together they form new chemicals that can have completely different characteristics for example if we have plain hydrogen it's a gas if I have plain oxygen that's also a gas but if I put those two gases together right if I put two atoms of hydrogen with one atom of oxygen and those atoms join together if they bond together to form a larger compound all of a sudden this new compound behaves completely differently now instead of two gases I have one single unit of h2o which you guys probably recognize as water right this is a liquid at room temperature so it's important to know or to understand how it is that atoms combine with each other and what types of characteristics they have because that influence is what they do in our body or how they behave in our body the chemical characteristics of the atoms that are present in our cells are going to determine the physiology of that cell or that molecule so they are important for us to learn it's a little cumbersome a little challenging typically for students to get through this chapter but we're gonna learn extremely important concepts in this chapter understanding how a lipid works or behaves for example is going to tell you how it travels through the bloodstream how it enters into cells understanding the structure of a protein is going to tell you a lot about the way things move in and out of the blood or you know whether or not things get filtered out of the kidneys these are these things that we're learning now in this chemistry chapter might not seem like they have anything to do with the human body to you right now but I promise you that they do all of these characteristics that we're going to learn in this chapter are gonna go on and tell you how things behave in the body so they are incredibly important for you to learn so bear with me all right so matter is refers to anything around us right anything that has any sort of space is referred to as matter and we said that matter so everything is made up of atoms an atom is one see unit of an element so one single unit of hydrogen or one single unit of oxygen now atoms are made up of subatomic particles right so sub-atomic like parts of the atom there are three different subatomic particles that can go into making an atom protons neutrons and electrons hey so atoms are made up of protons neutrons and electrons each of these has their own specific characteristics right so a proton Neutron and electron they could have some weight some size and they could have a charge they might be positive negative or neutral now different kinds of atoms have different numbers of each of these that's how they're different from each other this is what makes a hydrogen atom different from a carbon atom it has a different number of protons now when we look at these subatomic particles it's important that you understand the characteristics that go with each one of these protons are located in the nucleus of the atom if you look over here you can see kind of like a general structure for what an atom looks like in the very middle of the atom this area right here this is called the nucleus that's like a really dense heavy core that's where all of the actual mass and weight of the atom is in the nucleus so the nucleus the core of the atom houses protons and then you'll also see that there are neutrons in the nucleus as well Haiden looking at this picture you can see that right the nucleus is made up of these little red dots and the white dots and you see here that those are protons and neutrons so protons and neutrons are in the nucleus of the atom and then out here these little blue structures that you see these are called electrons electrons are not in this dense this dance nucleus instead they're constantly be rapidly moving around or orbiting around the nucleus in something called the electron cloud right so that's the general structure what an atom is gonna look like made up protons neutrons and electrons different types of atoms have different numbers of these things that protons and neutrons are in the nucleus the electrons are constantly moving around in the electron cloud so let's look at the characteristics of each of these particles protons have a positive charge so match up your peas right protons are positive so every proton that an atom has brings one positive charge so if you have an atom that has six protons that means it has six positive charges every proton also brings one mass unit so again if you have six protons then you're bringing six mass units to the atom you can think of mass like weight technically there is a difference in their in their description because weight implies gravity but don't worry about that just think of their masses like their size and their their weight all right till protons are positive and they have some weights to them they have some mass neutrons are neutral what that means what neutral means is no charge so they're not positively charged they're not negatively charged they're neutral hence the term neutron but they do have some mass to them they do have some weight every Neutron contributes one mass unit to the atom finally we have electrons those things that are always moving around orbiting around in the cloud electrons have a negative charge so they're opposites the protons protons are positive electrons are negative so every electron that an atom as brings one negative charge electrons are tiny they have such a low mass that it's negligible we don't even count it it doesn't matter it doesn't have any impact at all okay so we don't worry about their weight or their mass when we're talking about how much an atom weighs so looking at this right here I could say if I am looking at an atom right I have this atom right here and I want to know how much does that weigh what's the the mass of that atom how big is it I'm gonna look at two things if I want to know what the mass size of the atom is I'm gonna look at the protons and the neutrons both of those were the ones that have mass so the mass is going to be the number of protons plus the number of neutrons if I want to know the charge of the atom right is it neutral do the positives and negatives cancel out is it more positively charged or is it more negatively charged if I want to look at the charge I'm not gonna worry about the neutrons because they're neutral for charge I'm worried about the protons and the electrons so the charge is the number of protons those are all positive minus the number of electrons because the electrons are negatively charged hey if they have the same number of protons and electrons those will cancel each other out right six positives six negatives brings us right back to zero that's neutral I mean if they're not the same then the atom will end up having a charge either a positive charge or a negative charge hey we're gonna end up working through a lot of different examples where we'll look at an atom and figure out how many protons how many neutrons and how many electrons it has so you're gonna end up getting a lot of practice with this or just kind of bear with me work through it with me and by the end you should be really comfortable alright so elements an element is the most basic chemical that exists the elements are pure substances that contain only one type of atom so you can have a lot of atoms but they're all the same so carbon is an element hey I could have one atom of carbon I could have a hundred atoms of carbon I could have a trillion atoms of carbon but if it's all carbon its pure carbon that is the element carbon or a pure oxygen oxygen is an element pure hydrogen a hydrogen is an element if you guys think back to your high school chemistry when you looked at the periodic table of the elements the periodic table of the elements is a little table that contains little squares that represent each of the elements again hydrogen carbon oxygen sodium calcium these are all elements when we look at an element an element is determined by the atomic number of the atom so if it's atomic number one it's hydrogen hydrogen correlates with atomic number one atomic number six is carbon hey when you look at the periodic table each of these little squares will have a symbol in the middle for the element so that's the symbol for hydrogen up at the top you'll see the atomic number so hydrogen for example what you see here is atomic number one I'll tell you that atomic number tells us something about the hydrogen which we'll talk about in a sec at the bottom you'll have the atomic mass so that's the average weight of all of the hydrogen that exists in the world so the average weight is like 1.0079 4 I believe if I'm remembering that correctly off the top of my head hey that's the average weight of hydrogen so about 1 if you rounded that off right here underneath that you see that the element lithium is atomic number 3 right so you would have a square has L I at the top it has a 3 I'm not sure what the weight of lithium is so the atomic number tells us something about the element the atomic number tells you the number of protons that every atom of that element has hey so hydrogen we said hydrogen was atomic number 1 that means that every atom of hydrogen has one proton always if it does not have one proton it is not hydrogen hey the number of protons that are present in that in that atom will never change in a little bit we'll see that atoms can can change electrons they can give electrons away they can take electrons sometimes there's different atoms of an element that have a different number of neutrons but the number of protons is not going to change ok if it is hydrogen it has one proton always we said lithium right I just told you guys up here that lithium is atomic number three so what does that tell you that tells you that lithium has three protons every atom of lithium in the whole wide world has three protons hey if it doesn't have three protons it's not lithium carbon a carbon is something that's really common in the body carbon is atomic number six so every carbon every atom of carbon has how many protons six um now actually before we talk about isotopes before I talk about this page let's talk about electrons really quick as well so when we first look at an atom before anything has happened to it before it reacts with anything before it mixes with anything the basic element is neutral right it has no overall charge what that means is that the positive charges must cancel out the negative charges right they have to be the same and remember protons are positive and electrons are negative so what that means is that our basic elements before they react with anything they have the same number of protons and electrons later on they can change electrons but to start they have the same number of protons and electrons so while the atomic number tells you the number of protons it's also going to tell you the number of electrons pay so we can use atomic number to tell us the number of protons that are present and the number of electrons that are present now all we have left to figure out is neutrons right if I have know how many protons and then I can use that to find out how many electrons now I just need to know how do I find out how many neutrons there are and the way we find out how many neutrons there are is by looking at the mass of the atom or the overall weight of the atom so hydrogen for example we just looked at hydrogen remember I told you that hydrogen is atomic number one and its mass is 1.0079 four or something like that so that's about one right so let's see how many protons neutrons and electrons it's atomic number is one so that tells me it has one proton and because it's gonna cancel out the protons and electrons are gonna cancel it must also have one electron right because it's got one positive charge in one negative charge now I just need to know how many neutrons does it have I told you guys we're gonna use the weight down here to figure that out its overall mass remember is protons plus neutrons those are the two things that have weight protons and neutrons so if the weight is one and one equals protons plus neutrons we know it has one proton that never changes right so one equals one plus one zero okay so that means that hydrogen has zero neutrons so most atoms of hydrogen that you find in the world will have one proton one electron and one Neutron now in a little bit we'll talk about how it can react with things to do change its number of electrons right but otherwise this is this is what hydrogen will look like now if you notice this mass number that we have down here in the bottom this 1.0079 four that is not a whole number we rounded it to one right to make the math easy but if you look at that that is not a whole number and the reason is that I told you this is the average mass for all hydrogen that exists in the world so that means that there must be some hydrogen that actual weighs more than one not very much of it but there is some hydrogen out there some atoms of hydrogen that are kind of heavy that weigh more than one now the reason for this is because there are different versions of each element and those are called basic dopes so that brings us to this line isotopes are the different versions of an element based on its mass number or based on its weight so the mass remember equals the number of protons plus the number of neutrons okay electrons are tiny so when we look at the mass number when we look at the weight of an atom that's the number of protons plus the number of neutrons now different isotopes or different versions of an element have a different mass they have a different weight because they have a different number of neutrons so if I have two versions of hydrogen one of them weighs one mass unit and the other one weighs two mass units that second version that second isotope of hydrogen is heavier because it has an extra Neutron okay remember the number of protons is not going to change protons determine the element if it is hydrogen it must have one proton only that's not gonna change so if I have hydrogen and it's heavy it weights two mass units that means it must have an extra Neutron present okay so there are different versions of each element they have a different mass the reason their mass is different is because they have a different number of neutrons we call those different versions isotopes the atomic mass on the periodic table remember that's that's this one down here I told you guys that that shows the average mass of all ice they're all versions of an element hey that's why it's not a whole number because every once in a while will come upon an atom of that element that weighs either a little bit more or a little bit less than most of the others okay so here we see this example of hydrogen kind of spelled out for us these are the different isotopes right or versions of hydrogen that exist so each of these pictures each of these is showing us a type of hydrogen that exists in the world okay this first one right here is normal hydrogen typical hydrogen hydrogen one it has a mass number of 1 that means that this atom weighs one mass unit when we look at it when we look at the way that the atom is structured you see that it has one proton in the center right we know it has one proton because it's hydrogen hydrogen is atomic number one it always has one proton and then out here in the electron cloud you see that it has one electron that's good because remember they should cancel each other out the number of protons and the number of electrons is equal the positives and the negatives cancel the mass is 1 and remember the math equals protons plus neutrons so 1 proton 0 neutrons 1 plus 0 equals 1 that's how most hydrogen is in the world rarely every once in a while there's hydrogen - hey this hydrogen has a mass number of 2 hey it still has 1 proton because it's hydrogen it still has 1 electron right because the protons and electrons have to cancel but now we see that it also has 1 Neutron hey that's how it gets to a mass of 2 again the mass equals protons plus neutrons so one proton plus one Neutron then even more rare than that is hydrogen three it has a mass of three hey so if the mass of three equals the number of protons plus the number of neutrons hey and we know that the number of protons never changes so the mass of three equals one proton plus how many neutrons must this have two right two plus one is three so if you look here in the nucleus notice it has one proton and it has two neutrons that's how it gets to a mass of three it's heavy because it has more neutrons so these are all the versions of hydrogen that exist these hydrogen two and three are really rare most hydrogen does not look like that when we average all the hydrogen in the world together the average mass is 1.0079 four hmm because of the rare situations where every once in a while we have a heavy hydrogen that exists these are the main elements that exist in the human body you see the element listed right and then you see its symbol next to it so oxygen is an O carbon C hydrogen H etc and then the number that you see tells you what percent of the human body is made of that element so you can see that oxygen is by far takes the most weight present in the human body because our body is mostly water and water is h2o and oxygen is a lot heavier than hydrogen so most of the body's oxygen followed by carbon hydrogen nitrogen calcium phosphorus potassium but really these first few oxygen carbon hydrogen and nitrogen are the most common elements that we have in the body these are what we call trace elements down here at the very bottom these are things that are present in like tiny tiny little amounts in the body and then you see just these are some other ions that will be present in the body or like electrolytes they'll be present in the body I don't expect you to memorize anything from this this is just kind of fYI these are the the elements that we actually see in humans because not all elements are present in humans but these are the ones that you do see in humans okay so we're gonna spend a little bit more time talking about electrons because electrons are very important in determining how an element behaves or how a molecule behaves we said that the protons and the neutrons affect the weight or the overall size of the atom but when you want to know what that atoms actually gonna do you look at the electrons hey so we say that the electrons in the electron cloud right the electrons that are floating around out there in the cloud determine the reactivity of an element hey they determine the reactivity so reactivity again is is like behavior right how it reacts if I put two atoms together how are they going to react to each other are they gonna bond and form something stable are they going to blow up how they're going to react is determined by the electrons that are present so when we look at the electrons we know that the electrons are floating around in the electron cloud right now when we look at that electron cloud it's not just one big space with all the electrons crammed in the electron cloud contains electron shells or energy shells and think of them kind of like the floors on a house right you have the first floor and then you go up you use energy to go upstairs to go to the second floor and then you use more energy to go up to the third floor and more energy to go up to the fourth floor that's how these electron shells are there are different floors or different levels and it takes more energy to go out further and further and further now each of these electron shells holds a maximum number of the electrons so you can't just cram them all into the first show because it's easiest hey the first shall only holds two electrons so you put your first two electrons in there but if the atom has more than two electrons while the next ones have to go up to the next show now there are some elements that are huge right they've got a ton of electrons but most atoms that are present in humans only have up to the first four shells we're really just gonna look at the first few shells so you can kind of get an idea of the way that this works if you take chemistry you'll go through this and way more detail I just want you to have kind of a glimpse of this idea we'll talk through these few rules right here and then bear with me we're gonna go through quite a few examples and then this will all start to make sense to you so just kind of roll with it for now now an atom only has the minimum number of shells that it needs to hold its electrons so hydrogen for example has one electron that means it only has that first little shell right it doesn't have empty shells so if I had you know just me living in a house I don't need ten storeys to house myself I just need one storey I just need one floor so atoms only have the number of shells that they need to hold their electrons also the shells fill in order the lower shells fill first so the first electron shell will fill up with its two electrons and then the second shell will fill up with up to eight and then the third one will fill up with up to eight okay so they go in order finally the outermost shell that an atom has is called the valence shell this is the shell that's important the electrons that are in this outermost shell are going to Herman the bonding or behavior of the atom so the valence shell is different in different atoms if an atom only has one shell that's the valence shell because remember it doesn't have any empty ones so that's the outer shell if it has two shells then the second shell is the valence shell if it has four shells then the fourth shell is the valence shell peso the outermost shell is the valence shell and the electrons that are present in our outermost shell determine what the atom is going to do if it's gonna bond with another atom or not hate the reason for this is that atoms want a full valence shell or outermost shell atoms are happy when their outer shell is full and they will react with other atoms to try and fill up their outermost shell this is how atoms end up joining together to form larger things right so this is why if I have two hydrogen and one oxygen and I put them all together they're gonna join to each other right they're gonna bond with each other because they're all trying to fill up their valence show so we're gonna do a few little exercises here just to kind of start placing electrons in electron shells so you can see just kind of how this how this works how the electrons will fill the shells so and we see two atoms right this is an atom of hydrogen and this is an atom of helium hydrogen is atomic number one and its mass number one so let's see what does that tell us it's atomic number one so that tells us it has one proton protons are positively charged if it has one positive it must also have one negative so that means it also has one electron which is a negative charge it's mass is one and the mass remember equals protons plus neutrons so if the mass is one and it has one proton it must have zero neutrons so if we were to map that out right and draw that atom here you see it has its 1 proton in the nucleus in the middle and it has its one electron out here in the electron ship on the electron cloud now remember we're talking about shells which energy level or shell do we put that in we're not gonna draw all these shells and throw it out here in the third shell because remember the electrons go into their shells the first shell then the second then the third they fill in order hey since there's just one electron we're gonna put it in this first shell and that's what hydrogen looks like the first shell can hold a maximum of two electrons so hydrogen could actually fit one more electron in that show helium you I see over here helium is atomic number two and it has a mass of four so let's see what does that tell us the atomic number of two tells us that there are two protons and two electrons the mass is protons plus neutrons so if the mass is four that means we have two protons and two neutrons so two protons two neutrons and two electrons we know that in the center of this in the nucleus here in the middle that's the nucleus that's where we have our protons and neutrons so there are two protons and two neutrons all heavy in the middle now if we're going to place our electrons we have two electrons to place in the cloud we said that this first shell right here can hold two electrons so that's perfect we put two electrons there in the first shell and remember I told you guys that atoms will will do things they'll behave to try and fill their outermost shell well helium already has a full outermost shell right this this first shell is its outer shell all right that's the valence shell and in this case the valence shell is full without helium having to do anything it doesn't have to bond with anything or react with anything it naturally has a full valence shell that means that this is a really stable atom it doesn't really react with much because it's perfectly happy on its own um now these two right here let's do two more examples so you're really comfortable with it these atoms are a little bit bigger so now we're gonna have to move on from the first show we're gonna have to have more electron shells to hold more electrons um lithium is atomic number three right so that tells us it has three protons and three electrons its mass is six so that means it must have three neutrons as well hopefully that's that's comfortable you understand how to figure that map out so we need to place these three electrons Hey how many can we put in the first show two right we can only put two electrons in the first shell so you see here's one and here's two we still have one electron left we can't cram it in that first shell it's already full so that means there must be another floor right there must be another level out there so here you see this second electron shell now we put our third electron out there and this is what lithium looks like this second shell and the third just because of the way things still can hold up to 8 electrons each so the second shell can hold eight electrons and the third shell can hold eight electrons so if we look at this lithium right here lithium has one electron in this second shell and this shell can hold eight electrons so lithium is not happy right he's really reactive because this outermost shell is not full at all it's not even close to being full so he really wants to do something to try and get a full valence shell now we'll talk about what he would do in a second whether he would gain an electron or lose an electron this over here is is neon okay neon is atomic number ten and it's mass number is twenty so pause the video take a second and I want you guys to figure out how many protons how many neutrons and how many electrons hey and then press play and we'll move forward so the atomic number of ten tells you that there are ten protons right 10 positives and because the positives and negatives have to cancel out that means there must also be ten electrons if the mass is 20 remember that equals protons plus neutrons so mass of 20 we already know there are 10 protons so 20 equals 10 plus 10 so there's also 10 neutrons hopefully you got that perfectly fine now now we need to place these 10 electrons hey how many can go in the first energy show - so we put our two electrons here in the first shell right we had 10 total so now we have 8 left how many can we put in our second show 8 perfect right so we put our 8 electrons 1 2 3 4 5 6 7 8 in our second shell and neon has a full valence show right the second shell can hold 8 and it has 8 so its valence shell is full do you think that neon is highly reactive or is it really stable does it not interact with anything else hopefully you said it's stable right it's already happy its valence shell is full it doesn't have to do anything it doesn't have to interact with anyone else because it already has its valence shell full so neon and helium these are what we call the noble gases because they're all very stable they all have a full valence shell ok so who cares right why do we care about any of this why do we need to know where the electrons are or what the valence shell is the reason is because remember I said that the electrons in the valence shell determine how the atom or if the atom will bond with other atoms right is it gonna to join with another atom and build something bigger or not every chemical reaction that occurs in your body occurs because of the electrons in the valence shell every reaction our entire metabolism metabolism in our body happens because of these electrons in the valence shell so let's talk a little bit about these chemical bonds a chemical bond is the joining of two or more atoms to make a larger more complex structure hey this is how we are made we're made of lots and lots and lots of chemical bonds join the other trillions of atoms until we have these large things that are visible and tangible now a chemical bond this this joining of atoms occurs because of either the sharing of electrons so when two atoms come together and share electrons with each other or the gaining and losing of electrons so when jus atoms come together and one of them says hey I'm gonna take your electrons and this one says okay great bye you can have them okay so two atoms come together and they either share electrons or they take and give electrons that forms a chemical bond between those two atoms that holds those two atoms together to make a larger structure now again the reason that this happens the reason that that atoms will will you know trade or share the electrons in their valence shell is to try and fill up that valence shell atoms want a full outer electron show a full valence shell that's when they're happy right that's when they're most stable now again they can do this by by doing numerous different things with their electrons and depending on what they do with the electrons whether they share them or trade them there are different types of bonds that can exist so the different types of bonds include ionic bonds covalent bonds and hydrogen bonds hey we're gonna look at all of these in detail but just to introduce them right now an ionic bond is literally just a bond between ions a bond between ions and an ion is a charged atom remember we said that at the start atoms are neutral right they don't have a charge the positives and the negatives cancel each other out well Adams don't have to stay that way they can take extra electrons or they can give electrons away and then the positives and negatives don't cancel each other out anymore and you have an atom that has a charge right a charged atom is an ion so when we have two ions that are attracted to each other that's an ionic bond so an ionic bond is the attraction between cations and anions a cation is a positively charged ion so if the atom has a positive charge we call it a cation the reason it has a positive charge is because it gives away electrons okay it's an electron donor just roll with me we'll talk about this in detail in a sec anions are negatively charged they have a negative charge because they've accepted extra electrons so they have more of those negative electrons so overall the atoms negative it's an anion so if I have an atom right here that's positively charged and I have an atom right here that's negatively charged these opposites are attracted to each other right it's not just in dating opposites attract like a magnet right when you have opposite sides of the magnet they pull to each other magnets are created by pulling all the electrons to one side of the metal or one side of the magnet so when you have an atom that's positive in an atom that's negative those opposites attract and that holds those ions together that's an ionic bond now I have this larger structure instead of two separate atoms I have something bigger a covalent bond is a strong bond that occurs when we have two atoms that share electrons with each other hazal they come together nobody gives away an electron nobody takes an electron they just share them with each other hydrogen bonds are bonds that are based on partial electrical charges so instead of having a completely pot it's like instead of this instead of having a completely positive charge and a completely negative charge you have a part of a molecule that's a little bit positive and a part of a molecule that's a little bit negative and so there's a little attraction between them this is not gonna make any sense right now because you don't know what a polar molecule is right now but eventually we'll get to that and it'll make sense to you okay so just let's just keep going for now when chemical bonds join atoms together they form larger components right so instead of separate atoms we have something bigger that something bigger is either a molecule or a compound so technically the term molecule and the term compound can be describing different things a molecule exists when two or more atoms are joined together by strong bonds I don't care you can cross off this strong bonds part and down here this strong or weak bonds I'm not worried about getting into it that in-depth again it's not a chemistry class so a molecule is just when two or more atoms are joined together it doesn't matter what the atoms are it can be two atoms of hydrogen so if I have one hydrogen and it's bonded to another hydrogen that's two atoms so that's a molecule compounds are two or more atoms of different elements so that means that in order for it to be a compound there must be at least two different elements right are two different types of atoms so this right here where I have a hydrogen bonded like sharing electrons with another hydrogen that's a molecule but that is not a compound because all I have is hydrogen I don't have two different elements present hey if I had water right H - oh that's a hydrogen and another hydrogen but I also have an oxygen right so if I have h2o that would be a compound right I have two or more atoms there are three atoms and I have multiple elements I have oxygen and I have hydrogen so h2o is a compound do you think it's a molecule yes it's also a molecule it has at least two atoms so it's also a molecule according to that definition all of the compounds are also molecules right so if it's a compound it must have two atoms so it must also be a molecule but not all molecules are compounds okay so this the two hydrogen appear this was a perfect example that counts as a molecule but it does not count as a compound so make sure you're comfortable with this so if I give you you know whatever example make sure you can tell me is it a molecule is it a compound is it one atom you know what is it so if I said oh two that means that I have one oxygen bound to another oxygen is that a molecule yes is that a compound no is that an atom no it's two atoms right there are two oxygen there if I had c6 h-12 o-6 you'll see that a lot because that happens to be the chemical formula for glucose and we talked about glucose sugar a lot but that means there are six carbon twelve hydrogen and six oxygen all bound together is that a molecule yeah there's at least two atoms is that a compound yeah there's more than two atoms and there's three different elements there's carbon hydrogen and oxygen it's at an atom no that's a lot of atoms right that's twenty-four atoms what about carbon is that a molecule no is it a compound no that's an atom right it's just one single carbon it's just one of them okay so we know that atoms interact with each other by forming bonds and when they do this they form larger units called molecules or compounds we know that the way atoms do this the way that atoms form bonds is by utilizing their valence electrons right their outer electrons and the reason that they do that is to try and fill up their outermost shell they want a full valence shell so now we're gonna talk about those different types of bonds that occur in more detail right we said ionic bonds covalent bonds and hydrogen bonds we'll go through each of these and quite a bit of detail so we'll start with ionic bonds I said that ionic bonds are bonds between two ions make sense and an ion is just a charged atom so this is an atom that's not neutral it's either positively charged or it's negatively charged that must be in order for it to be charged the protons and electrons have to not be equal right remember when protons and electrons are equal they cancel each other out but if they're not equal right if the positive charges and the negative charges are not the same then you end up with an ion you end up with an atom that has a charge to it either positive or negative charge so when we have an ionic bond we end up with a positive ion and a negative ion and the opposites attract so in an ionic bond what happens is we have two atoms come together right and they're both trying to fill up their outermost shell one of the atoms which we called the electron donor because he's gonna donate electrons he's gonna give electrons away this guy loses one or more electrons now because he's giving away those negative charges he ends up becoming a cation meaning he ends up having a positive charge hey think about it if you started out neutral if I started out with six protons which are positive and six electrons which are negative I started out like that and I gave electrons away say I gave one electron away so now I only had five now I have six you know plus six minus five overall that's plus one that's positive so overall that atom would have a plus one charge because he gave away those negatively charged electrons hey again a positive charge makes something a cation if you write the word cation look it has a big whoops it has a big positive in the middle right cation right cations have a positive charge so you've got an electron donor and then the other atom is the electron acceptor he takes those electrons that were given away and because he's taking those negative charges now he's gonna have more negatives and he's gonna become an anion anions have an overall negative charge okay again because they have more electro then I have to Adams ones positive and ones negative and opposites attract so they're pulled together just like a magnet and those two atoms are held together like a magnet forming an ionic bond so here's an example of an ionic bond forming between two atoms a sodium atom and a chlorine atom and this forms something called sodium chloride that is table salt so when you put salt on your food this is what you're putting on a few your food the reason the sodium and the the chlorine attached to each other is because of their valence electrons and because they form an ionic bond together so these this shows us like how they start okay so when we have two atoms and they have not interacted with each other yet this is what they look like so let's start with sodium sodium is up top the symbol for sodium is na I don't know why but that's it so na is sodium you should memorize that because we'll talk about sodium a lot and I'll always write na I won't write out the words of iam so sodium is atomic number 11 okay so think about what does that tell us that tells us it has 11 protons which are positive and 11 electrons which are negative let's place those electrons okay we have 11 electrons to put in the shells how many go in the first show - right so you see these there's one and two then not the first shell full and I have to go out how many can go in this second shell eight right so you see one two three four five six seven eight right so that's 10 that we've put in there so far we have one more so we have to go out to the third shell so this third shell out here has one how many can we put out there in the third shell we can put eight right so sodium has one in this third shell and it really wants a full valence shell so it either has to take seven electrons from something I don't that's just not gonna happen no atom is gonna give away seven electrons so that's it's never gonna be able to take seven electrons to fill up that third shell the other thing that the sodium can do is give away this one electron it only has one measly electron out there if it gives that electron away this third shell disappears remember there are not gonna be empty shells so if there's not that one electron anymore this third shell goes away and the sodium looks like that and now if you look at this second shell it has eight its full that's now happy so that's exactly what happens the sodium donates an electron gives an electron away so if you look over here at the second picture now this sodium still has 11 protons right that never changes but now it only has 10 electrons so it's not balanced anymore now there's more positive charges so overall this sodium has a positive charge it's not a sodium atom anymore it's now an I on because it's charged so you see next to the symbol it has this little plus sign and then you look down here notice we've wrote this little plus sign because it's now positively charged now is that an anion or a cation hopefully you said cation right sodium is a cation it is positively charged now let's do the chlorine hey if you feel comfortable just doing this process with the chlorine right now go ahead pause the video and do you don't have to like you can try it just see if you can talk through it yourself or you can go through it with the video with me chlorine is atomic number 17 that tells us it has 17 protons and 17 electrons so let's place those 17 electrons two can go in the first shell eight can go in the second all right so that's ten that leaves us seven more to put in the third shell so chlorine has seven in this third shell out here and it can hold eight so chlorine is dying to get one more electron right it's like it's so close to having a full valence shell that just as much as sodium wants to give one away chlorine really wants to take one so they're like perfect for each other right they're a perfect match so what that's exactly what happens this electron that sodium was giving away it gives it to chlorine chlorines happy to take it on so if you look over here this is what chlorine ends up looking like now it has eight electrons in this third shell which means the shell is full and he's happy however now he has 18 electrons right still has 17 protons because that's never gonna change but it has 18 electrons so it's got more negative charges so if you look here we say that this is negatively charged and down here instead of having a chlorine atom we have a chloride ion right and next to the symbol of CL we have this negative because it's negatively charged so now it's a chlorine anion so sodium is the cation chlorine is the anion and opposites attract so now these two ions are held together because of this attraction between the positive and the negative charge and that gives us this sodium chloride so that's an ionic bond so now we'll go through covalent bonds um a covalent bond occurs when there's sharing of pairs of electrons between atoms so instead of having two atoms and one just gives the other one electrons they neither one of them wants to give anything up so instead they come together and they share pairs of electrons they can share one pair two pairs three pairs when they share electrons one electron is donated by each atom to make that pair so if two atoms come together and they're gonna share a pair of electrons this guy will donate one electron and this guy will donate one electron and then they share those two together if they share one pair of electrons we refer to that as a single covalent bond we draw it with one line so like a CH one line H that's telling us that these two hydrogen are sharing one pair of electrons they can share two pairs of electrons that's a double covalent bond so like carbon with carbon so each of these lines is representing two electrons three pairs is a triple covalent bond that's not really common in the human body we're really just gonna look at the way that a single covalent bond is formed and that's fine just understand that double covalent bonds and triple covalent bonds do exist alright so here we see some covalent bonds the first one here don't worry about these I just want to kind of show you really simply how this works the first one here shows you a CH - right that just means that there are two hydrogen bonded together and this here you see the H and then the one line and then another H that one line is telling you that there's a single covalent bond that those two hydrogen atoms are sharing one pair of electrons with each other now if you think about hydrogen hydrogen remember each hydrogen has one electron so he has his nucleus in the middle like this and then his first electron shell has one electron in it and remember that first shell holds two electrons so they both if I have two hydrogen atoms like this they both really want one more electron right so this guy can look at the other one and be like hey give me yours and he's like no you give me yours so instead of one of them stealing it from the other it's better if they just come together and share what they have and this is what ends up happening they fuse their electron shells together okay and then they have two electrons that are able to move through anywhere in that area so this one over here this guy is like hey I've got a hold of two electrons in my shell I'm happy this guy over here also thinks hey look I've got two electrons in my shell I'm happy hey remember these electrons are moving super fast right they're moving all around through these shells really really rapidly so both atoms think that they have those electrons both atoms are are happy and because of these fused shells they are attached to each other they are held together because of that covalent bond now there is no charge involved there's no change in the charge because the tons and electrons still balance out right I still have one positive right here and one positive right here one negative and one negative so they still balance with each other now um well talk about as we go forward the next few slides I'll talk about how sometimes these bonds can be a little bit unbalanced as well but in this case they're completely balanced so that there's no charge involved this is showing us a double covalent bond with oxygen when we have two oxygen atoms and the only difference there is instead of only sharing two electrons they're sharing four so there's one pair and then there's another pair that are being shared so each of these oxygen feels like they have eight electrons in this second shell right this guy has 1 2 3 4 5 6 7 8 so he's happy and then the same thing with this one over here he has 1 2 3 4 5 6 7 8 they're just sharing more electrons in this case to try and fill up their valence shell or their outermost shell so these are covalent bonds now there are actually two types of covalent bonds right covalent just means that the atoms are sharing electrons with each other now they can share equally where they both kind of have equal custody of those electrons or they can share unequally where one of the atoms is kind of like a big hog and he holds on to those electrons for much more time than the other guy and they result in two different types of molecules and this concept is very important as we go through anatomy and physiology so kind of pay attention if you need to take a break first do it so a non polar covalent bond happens when there is equal sharing of electrons and this forms a balanced molecule with no partial charges so this happens anytime you have two of the exact same atom sharing electrons so if I have two hydrogen right they're the same they're the same size the same strength so they pull in those electrons the exact same it's perfectly balanced o two right two oxygens they are the same this also happens when I have um I'm gonna write it up here when I have long hydrocarbon chains so for example in a lot of molecules in the body you'll have like carbon carbon carbon and they're surrounded by hydrogen's like this okay and when you look at this you can kind of see like how perfectly symmetrical it is but those are all nonpolar covalent bonds there's equal sharing the molecule is completely balanced there's no charges whatsoever it is non-polar a polar covalent bond exists when there is unequal sharing of electrons so in this case you have two atoms sharing electrons and one of them is a hog right he's a bigger stronger atom he's more electronegative he hangs onto those electrons for much more of the time that means that the negative charge spends way more time or in this area than it does in this area so you end up with a molecule that's what we called polar it's not balanced it has a negative pole and a positive pole now these are not ions right it's not a complete positive and a complete negative it's just a partial positive it's just you have this this molecule this large substance and there's an area that's kind of negative and there's an area that's kind of positive hey there are lots of examples of molecules that are polar glucose for example sugar is a a polar molecule but the classic polar molecule is water hey or h2o whether or not a molecule is polar or nonpolar is going to be incredibly important when we talk about its behavior okay so this is an important contact polar just means the molecule is not balanced it's got kind of charges present in it nonpolar like fats are nonpolar that means there's no charge so let's look at on water and see why is water a polar molecule why does it have polar covalent bonds water is just h2o right we've got oxygen and oxygen has six electrons in this second shell so it really wants two more electrons and then we have our hydrogen's right two hydrogen atoms this hydrogen over here has one electron right and it really wants one more so it'll come and it'll share a pair of electrons with the oxygen right and that gives us this bond here but that makes this this hydrogen happy because he's got his electron and oxygens gotten one more but he's still not done he needs another one then he only has seven of me so he needs another hydrogen atom to come on in and so this hydrogen then gives another electron as well so you see that the oxygen is sharing electrons with a hydrogen here and a hydrogen over here now just looking at that you can see that oxygen is much bigger right he's a much bigger stronger atom he has a lot more of these these positive protons in the middle that are gonna pull those electrons over right so the electrons spend way more time over here than they do over with the hydrogen's that means that there are negative charges present on this side more than on the other side so that creates a polar molecule parts of it are kind of negative that's what this Sigma sign right here means like partial so there are two partial negatives over here and then each of the hydrogen's is like a little kind of positive zone so there was a partial positive over here by the hydrogen and a partial positive over here by this hydrogen so water is polar it has partial charges present now the reason that that is important is because that allows polar molecules that have partial positive and partial negatives they allow for us to go to our next type of bond which is a hydrogen bond a hydrogen bond is the attraction between the slightly positive and slightly negative portions of polar molecules because remember opposites attract right that's how the ionic bond works we've got a positive and a negative and opposites attract well with a polar molecule it's not a full positive and a full negative but it's still kind of charged so the whole molecule can arrange itself so that the negatives are by the positives of another one right and then the positives by the negatives of another one and you form slight attractions between the molecules those are hydrogen bonds so if you look here you see a bunch of water and you see that the water molecules have arranged themselves so that there's attraction between the positive and negative parts of the polar molecules so like if you look at it this is the positive part right the hydrogen that's kind of positive and it's arranged itself so that it's close to the the negative oxygen now even then over here this positive hydrogen has a slight attraction to the negative oxygen right this positive hydrogen has a slight attraction to the negative oxygen so they're not like full bonds with each other but there is a slight attraction here between these partial charges these these opposites hydrogen bonds between water molecules are the the reason that water behaves the way that it does and this is really the reason why life exists water is incredibly important in the behavior of our life really and our bodies are made up of mostly water and the reason that for example sweat cools us off is because of these hydrogen bonds the reason that salts and sugars go into solution they dissolve in our bodies is because of these these partial charges the the polarity of water so the fact that water is polar is very very important to its behavior hydrogen bonds between water molecules happen to be the reason for surface tension so like if you see a water bug walk on the surface of water right the reason that he can do that or like a leaf the reason that Abraha leaf floats on the top of water it's because the water molecules are attracted to each other and they don't want to separate from each other there are hydrogen bonds holding all the molecules together so it takes a certain amount of force to push through and break that bond obviously I can easily break the bond to push through the water but there is a slight attraction there that's why like if you've ever filled up water to the very top of a cup it'll actually go higher than the rim before it pulls over because the water does not want to separate from the other water molecules there are slight hydrogen bonds present there these last few slides you guys are just examples of different like chemical notation so just the symbols that we use when we're writing out um you know chemical formulas and whatnot so I do recommend that you just kind of read through this on your own a little bit this is just like for example if we have one hydrogen atom we just write the symbol an H if I have two hydrogen atoms notice they're separate it's not two hydrogen bonded to each other it's two separate hydrogen then we write the number two before it so that's telling me I have two hydrogen I've got one here and one here if I wanted to tell you that the hydrogen were bonded together that it was a molecule in that case the two would be a subscript like this okay so yeah right here when the two hydrogen are bonded and it's a molecule then the two is the subscript hey or like this right here means there are two hydrogen and one oxygen all bound together hey if they were separate I would put two hydrogen right and then plus one oxygen those are all separate from each other but when it's written like this that means that they're all bound together this is just showing you a reaction so for example two hydrogen plus one oxygen all separate what you see here if they all join together right the arrow showing me where it's going they all join together to form h2o water equations have to be balanced so there has to be the same number of atoms on each side like atoms don't just disappear so for example over here we have two hydrogen and two oxygen well look over here we only have one oxygen it's like what happened to the other oxygen you have to account for it in some way atoms don't just go away or they don't just come out of nowhere so equations have to be balanced on either side and then finally ions if something has a charge we put it up here superscript up at the top if there's just the plus sign that means it's one positive charge if it's just the negative sign that means it's one negative charge if it's more than one we put the number so two plus calcium for example it's a cation with a 2 charge a charge of two to positive charges sodium only has one positive charge so it just has the plus sign and I'm gonna leave right here I'll start the next lecture with this slide because I have taken up every last second of our hour and 20 minutes together so we'll start the next presentation with this slide right here if you all have any questions please feel free to shoot me an email and then I'll talk to you tomorrow bye have a good day