 All right, guys, let's start on chapter two. Again, I want to mention we'll push that quiz to back to Friday. So we don't have to worry about it over the Labor Day weekend, of course. I'm sure you guys are already so ready to go to the Labor Day business, even though you've been in school for a week and a half. But I am too. So I can imagine. But the quiz two will be over chapters one and two. Chapter two is not too much more than chapter one, chapter one's like all the business words. Chapter two is just mostly talking about the periodic table when it shouldn't take us too much time to really understand that, OK? So let's go ahead and start chapter two, atoms and molecules. OK, so what is an atom? An atom is the basic structural unit of an element. So it's the smallest unit of an element that retains the chemical properties of that element. So what is an element? Well, if we look up here at the periodic table of the element, each one of these boxes represents a unique element that you find in nature. Well, some of them can be found in nature. Others, like the ones that have the outline things up here, are man-made. Those ones are not found in nature. You have to use some sort of big super-collider to make these or various nuclear reactions. Normally, in chemistry class, we represent atoms as little balls, OK? So if we look at this picture here, we see atom of a particular element, orange, and another atom of a particular element, green, OK? These atoms can combine in various ways, or maybe not combined, due to their reactivity, and form different sort of substances that aren't the same as the original substances, OK? So if we look at this, this combined picture here shows a chemical composition of what would be a compound, OK? Compound would be something that's composed of two or more different atoms. We'll talk about that later. There is this guy Dalton in the 1800s, 1870s. So this is really when chemistry really started to get going. And he came up with this atomic theory. Most of the atomic theory still holds true today. All the red statements hold true. The black ones are very close to being true, but just slightly false. OK, so all matter consists of tiny particles called atoms. That's still true. An atom cannot be created, divided, destroyed, or converted to any other type of atom. That's almost true. They can't be created and divided, well, they can be divided into electrons and protons and neutrons, which we'll learn about in a little bit. But they can also be converted to other types of atoms if you produce them in nuclear reactors, OK? Like the sun is a big glorified nuclear reactor that takes hydrogen atoms. And since there's so much gravitational pressure in the middle of the sun, it'll squish those hydrogen atoms together and make a helium atom. And that's why the sun gives off all this radiation, OK? That's why we live on the Earth, because the sun was able to give us life, and we could grow. But it was because of this nuclear. So as you can see, atoms can be converted to other types of atoms. It just takes very extraneous circumstances to do so. OK, we can't do it in the laboratory very easily. The atoms of a particular element have identical properties. This is almost true again. Again, there are some atoms that have isotopes, different isotopes, so they weigh slightly different, even though they have the same chemical properties. Like some bromine atoms weigh 77 AMU, and some bromine atoms weigh 79 AMU. So just the mass is slightly different. This is due to the amount of neutrons that they have in their nucleates, OK? We'll get into that later. You don't have to worry too much about it right now. But just know that different types of atoms are the same atom with different masses, different types of properties. All the rest of the postulates hold true. Atoms of different elements have different properties. Of course, atoms of different elements combine in simple whole number ratios to produce compounds. So you can imagine carbon dioxide. The compound carbon dioxide is, I'll draw a structure of it, any time you have a carbon that combines with two oxygens, it will always be carbon dioxide. It will always have those properties of carbon dioxide. And it will always carbon dioxide. You can look at it the other way. Carbon dioxide will always be composed of the simple whole numbers, 1C and 2O's, OK? Just like if we have carbon monoxide, it'll be 1C and 1O. And the properties of every molecule that have those two combined will have the properties of carbon monoxide. Chemical change involves joining, separating, or rearranging atoms. Of course, you could imagine, like we've done before, taking two sodiums and one molecule of chlorine. We can rearrange these atoms to form two. This has different properties than this, which have different properties than this. They all have different properties. All depends on the types and the ways that the atoms are combining with each other to form these compounds. OK, so yeah, we learned the simplest form of matter is an atom. Well, unfortunately, that's not the case. Because if it was, then we wouldn't have to learn any more about it, right? But there were experiments after that that figured out, well, they're simpler forms of matter. That atom is actually composed of other things, an electron and a nucleus. So atoms consist of three primary particles, electrons, which are negatively charged particles, which you'll find. Let's draw kind of a depiction of an atom. We'll draw a depiction of a helium atom, a nucleus, like Justin. It's really kind of a shell, so don't think of it like a kind of a orbit like planets. So it's kind of like you got a whole sphere around this thing. And in that sphere somewhere, you're going to find two other dots, we'll color them in different colors. That's what a helium atom looks like. Again, that's a representation of a helium atom. It's not really a helium atom. The electrons are the blue things. They're the negatively charged particles. So we draw them, or a way to represent electrons. So if you ever see me draw E with a minus there, that's an electron. That's the way I'll be referring to electrons from now on. So you see we've got these two electrons out in this orbital here. And then we've got this small dense, what's not as a positively charged region in the center of the atom, that green and white thing, a tightly bound subatomic particle, subatomic, meaning below atomic, what? Subatomic particles, we got protons in there. So the protons may be the white things. So we would say two protons, and that's just a P with a plus because the protons are the positively charged subatomic particles. And then we've got the green guys or the yellow guys, whatever it looks like to you. They're called the neutrons. And we've got two of those as well. And we'll say N with a little 0, meaning no charge, or N not. So those are uncharged particles. So notice, remember when we were talking about different isotopes of atoms? The different isotopes of atoms have the same number of protons. It's their neutrons that are different. That's what gives them the different masses. So I don't know, chlorine, one chlorine atom could have 37 mass. So it would have 17 protons and 20 neutrons. And another chlorine atom could have 35 mass. It would still have 17 protons. But it would have 18 neutrons. So the difference is the difference in neutrons. So what it really comes down to, which you really want to start thinking, is that the composition of the atom, the type of atom that it is, is only suggested by the amount of protons that the atom has in its nucleus. So any atom that has 28 protons in its nucleus is a nickel atom. What we'll find is you see these little numbers up in the right-hand corner there, 1, 2, 3, 4, 5? That tells you how many protons the atoms have in their nucleus. That's known as the atomic number. All of these are going to be given to you on the test. Of course, it's going to be, I'm not going to unbolt that every time we have a test. So it's going to be kind of your cheat sheet. Notice all these numbers all over this periodic table. This is all you need to know about the periodic table. You need to know why it's set up that way and such and so forth. But once you learn that, it's all given to you. You don't really have to memorize anything. So three primary particles, electrons, protons, and neutrons. Electrons are outside the nucleus. Protons and neutrons combine to form the nucleus. So you can see kind of what I've depicted there, the modern model of the atom, is a dense nucleus of protons and neutrons that counts for virtually none of the volume, so very little of the volume, and virtually all of the mass. In fact, protons and neutrons are quite heavy compared to electrons. So the probability clouds, so that electron cloud or that electron shell, accounts for virtually all of the volume and virtually none of the mass. A good representation people usually will show in textbooks. I think there's a picture in your textbook, is they'll have a person holding a marble in the middle of an Olympic-sized state. That marble would represent the nucleus, and the Olympic-sized stadium would represent the electron cloud. So you can imagine how big the electron cloud is relative to the size of the nucleus. If you think about how big a marble is relative to an Olympic-sized stadium. Very big and very small, I guess, if you think about it. So in a neutral atom, which the periodic table shows only neutral atoms, the number of electrons equals the number of protons. So helium, this helium atom, is a neutral atom, because we've got two protons and two electrons. You can imagine atoms where they weren't neutral. Let's show. We'll do lithium. It's going to have how many protons does lithium have? It's a lot of protons. And its mass number is 7, so it's going to have, so protons and neutrons weigh the same amount, remember, and they account for all the mass. So the bottom number there, that's the mass number. So that's essentially 7, 6.9. So if we have three protons, we're going to have four neutrons, because 3 plus 4 equals 7. The reason why that says 6.9, 4 and not 7 is because there's different isotopes of lithium. So some of them weigh 7, some of them weigh 6. So if we look at the electrons' clouds, I just got two shells. In the first shell, we've got two electrons. In the second shell, we've got a third electron. So it's going to have two electrons. Don't worry, we'll get to it. Electrons have charges that are equal in magnitude, the opposite. So one is negative one, the other one is positive one. Even though the mass of the two particles are quite extensively different. Yeah, a neutral atom has no electrical charge. Some atoms, so this is a neutral atom. Let's make it instead a positive atom. We have three protons here, three electrons. If we remove one of those electrons, we only have two electrons and three protons. It's still a lithium atom, because it's got three protons, but it's going to be a lithium atom that has more positive charges than negative charges by one. So we would call it lithium plus. So what do we do here? Let's look at lithium regular. How many protons does it have? Look at there. Three protons. So it takes a list right now. So we know that the periodic table only shows us neutral atoms. So how many electrons does lithium have when it's neutral? Three, right? Because it has to be found. If we take one of those electrons away, how many electrons would lithium have now? Two. So we'd have two electrons. So three minus three equals what? Zero, right? Three minus three equals zero. How many protons does it have to have because it's a lithium atom? Three always. So what is three minus two? One. And chemistry, we say positive one, or what we're showing you like that, we just put a plot. That's how you do it. That's when lithium loses its last electron. Although we'll get to learn more and more in depth about this. That's called a Baylind's electron. The outer shell is known as the Baylind's shell. And they like to lose or gain Baylind's electrons. In fact, that's where all reactivity comes from. It's just that Baylind's shell. Nothing else. OK, so like we said, there's some common symbols of electron, proton, and neutron. Ironically enough, a proton can be represented as P plus or as H plus, hydrogen plus. Because of course, how many protons does a hydrogen atom have? One proton, right? Do you guys remember where you could find the mass number up there? I know we haven't gotten really in depth to it yet, but it's that bottom number, right? Bottom number right there. So that number is essentially what? It's one, right? So remember we said that number is the combination of the amount of neutrons and protons that we have in the nucleus. So how many protons does a hydrogen atom have in its nucleus? Or how many neutrons does a hydrogen atom have in its nucleus? Zero, right? Because one plus zero equals what? One, right? Is that number essentially one, or is it essentially two? One, right? So it has one proton, but it can't have any neutrons, right? Right? Does that make sense? So how many electrons does the neutral hydrogen atom have? One. So we've got one proton and one electron, right? What would happen if we took that electron away? What would we have left? Well, let's draw this one. So hydrogen has, what did we say, one proton and one electron, right? If we remove that electron, what would we have? Would that hydrogen have any, how many protons? How many electrons? Zero. Zero electrons, right? So what would we represent this H of? Here, H plus, right? What is H plus essentially? Just one proton, right? What do we have left? Just that proton, right? So in fact, you'll see this especially when we get to acid-base chemistry. This will be representation of a proton, H plus, because it essentially is just a proton. That's all it is. So you've got to know the symbolism, both this P plus and this H plus, because I'll be using them. And I don't want you to get too confused, because I'll use them just because that's what I use. And you're going to have to just deal with it, I guess, unfortunately. But you'll get used to it eventually. For right now, I'll try to only use the P plus for protons. Just so you guys can step your way into it. OK, notice the charge here, negative one for the electron, positive one for the proton, zero for the neutron. Notice the mass of the electron is much, much smaller than the mass of the proton and neutron, which are essentially the same. So you can see here, this is essentially one, AMU is the mass unit that we use for measuring atoms, protons, and neutrons. So you're going to have to get used to this unit AMU. And we'll show you how to do calculations from grants to AMU. How small the electron is relative to that. So which subatomic particles are represented by the pink stuff here? That's electrons, right? Clearly, because they're outside of the nucleus. What about the yellow and blue stuff? Good job. And what is this whole thing combined called? That little wall. Hopefully you got that. OK, so let's go back and look at the periodic table and look at these different elements. In fact, the periodic table represents a 2D element, like we said before. And these are the elemental symbols. So for neon, as in usually, or always, you'll find the periodic table represents elements in a one or two letter symbol. These elements down here now have one or two letter symbol names. I think they're all two letters. This just means a 110, 111, 112, because this was before they were actually named. So they just were named, I think, at the beginning of 2010. We've got all the way. They're still making advances, if you can imagine, on the periodic table, which is amazing, I think. Yeah, are they not on there either? This shows a number. Yeah. So they're not even on there. So they're so new that even the new chemistry book doesn't happen. So symbols and formulas. A unique symbol is used to represent each element you need. Li is not the same as Zm. The symbol is based on the name of the element, lithium. That's why it's called Li. Some of them are weird, because they're either the Latin or the German name of the element. Like element 26, Fe, is iron. So you're going to have to kind of twist your thinking to realize that this is named after the Latin name of iron, which is ferris, or ferris. Elemental symbol for oxygen, chlorine, neon. That's the name. A lot of periodic tables will give you the name. I'll give you a periodic table that gives you the name of the element. So I don't expect you to memorize the name. So don't waste your time. You go on to 1411, then we'll start memorizing names of elements. But for right now, just concentrate on what the numbers of the periodic table mean. Also, we've got this number up at the top, and this periodic table is in the top right. You'll either see it there or at the very top in both periodic tables. That number represents what we call the atomic number, the number of protons in the nucleus of that atom. And this number on the bottom, again, represents the mass number, and that's the number of protons plus neutrons in the nucleus. So notice, the electrons don't contribute to the mass of the atom. They're so tiny that they don't contribute to the mass at all. Let's just do that. I think we'll get to it in a second. Yeah, we'll get to it even more. Notice, you can see that these are all different elements, chlorine, chlorine, bromine, and iodine. Oh, well, we don't have fluorine. See, chlorine is this yellow gas, bromine is this orange kind of purplish liquid, and iodine is this purple salt. So they all have different chemical properties. Even though these ones, what you'll find is elements that are in the same column here. We call these either columns or families. We call them families because they behave very similarly. It's because they have the same amount of electrons in their valence shell. And remember, the valence shell determines all chemical reactivity. So it doesn't matter how many neutrons, blah, blah, blah, blah. It's all about the valence shell of electrons that determines chemical reactivity. So that's what we're going to concentrate most on in this class. But even though these guys are in a family, they all have similar properties, but they're not the same properties. Just like in your family, you guys kind of look the same, but you're not. So let's talk about compounds now. So a compound formula, so that would be the formula of a compound like CO2 there, can be represented in a variety of ways. Notice on the board already I've represented CO2 like that and like that. Those are different formulas for CO2. One of them is the molecular formula, which is that. The other one is the structural formula, which is that. So this is, if you were a little person, small enough to see a carbon dioxide molecule, that's, well, it would kind of look like that. It wouldn't say C and O. It would actually look more like a sausage like that. That's what a carbon dioxide molecule would really look like if you were able to see it. And in fact, this is what a water molecule would kind of like a blob with two little things on the bottom. So this is called a ball and stick model. We could draw the ball and stick model for carbon dioxide if we wanted to. The space filling model would be kind of that sausage. Get it? I guess we could fill it in more, and I think you can figure it out. OK, so here's some examples of compound formulas. So here's going to be the space filling model of them, methane. This is the natural gas. The stuff that comes out of your Bunsen burner before you like that, we haven't used a Bunsen burner yet. But if you have a hot water heater at home, this is the stuff that comes out of a hot water heater. Or if you've got a gas stove at home. This is what comes out of the gas stove. A water, of course, you guys are familiar with that stuff. Carbon monoxide, don't get too close to this stuff or it will kill you. That's why you've got carbon monoxide detectors in your house, right? Carbon monoxide looks a lot like oxygen. And in fact, your enzyme that binds oxygen, anybody know what an enzyme is? It's these things inside of you that kind of do stuff, the stuff that does stuff inside of you, OK? So one of the enzymes grabs oxygen and allows you to breathe, to respire, actually. It's called respiration, and it's not the same kind of breathing in and breathing out that you're used to. It's something that's totally on a molecular level. Still call it respiration, though. But that enzyme actually binds better to carbon monoxide than it does to oxygen. And when it binds to carbon monoxide, it won't let it go because it binds so well, OK? Won't let it go. And then, of course, when that enzyme interacts now with an oxygen molecule, it won't let that carbon monoxide molecule go, so it can't interact with that oxygen molecule when the oxygen just flows away. That's why carbon monoxide will kill you, because it won't let that enzyme bind to oxygen. And then hydrogen peroxide, this is definitely hormone-cutting stuff, very reactive stuff. That's why it kills everything. OK, so let's practice with some compound formulas. Well, this stuff here is a liquid known as carbon disulphide. It has a very similar structure to carbon dioxide. Remember, I said that these are families. Look, oxygen and sulfur are in the same family. That's why they have a very similar structure, carbon disulphide and carbon dioxide. Let's look at the structural formula of carbon disulphide. Is that very closely resembling carbon dioxide? But notice carbon disulphide is a liquid. Look at carbon in its atomic form, that black solid. That's like coal. Or actually, diamond is carbon in its atomic form, too. So graphite is stuff that you're writing with. That is carbon in its atomic form. And diamond is also, if you've got a diamond ring, you can kind of compare them. But they're both carbon in their atomic form. It's pretty interesting. But anyways, look at this stuff. And then this stuff is sulfur. But if you combine these guys, you make this clear liquid. It's kind of interesting, right? So you can do the difference here, really emphasizes the difference between chemical and physical properties of these different substances. If carbon dioxide, well, I'll give you the answer to this. If carbon disulphide contains one atom of carbon for every two atoms of sulfur, what's the chemical formula for carbon disulphide? Well, I didn't really give it to you, but what would be the chemical formula for it? It's implied by the name, right? One carbon, two sulfur, two sulfur, guy sulfur. That's their valence electrons. We'll get to that later. Yeah, sorry for putting dots, but these are just little electrons that those solvors still had leftover that they didn't use to bond. In fact, what you'll find is that those valence electrons, they're used for bonds. That's what bonds are formed from is the valence electron. So this is actually two electrons and this is two electrons. So in between this is oxygen and carbon, there's four electrons that are sticking those things together. Those electrons are like glue. So like glue for the atoms to stick together. Don't take that representation too far, but you can kind of make them stick together. OK, let's go back to the periodic table of elements and look at the symbols and form off. So remember we said that this is the atomic symbol of the particular element that you're interested in. Is this the x in the middle? That's as simple as that. z, this is going to be the atomic number. OK, what did we also say was the atomic number? Is this little one up in the top right? Huh? The number of protons. Yeah, that'll be the number of protons. So whenever you're representing them like on the test, or something, and I say draw the entire atomic symbol, you would want to start drawing things like this. OK? So you'll get so used to this by the end of next week that he'll be old hat. Here's the atomic number. A, there is the mass number. And C is the charge of the particle. For every one of these guys up on the periodic table, the charge of the particle is 0. This isn't the way that the element is represented on the periodic table. OK? So this is different to the way the element is represented on the periodic table. So watch out. What will happen, what you'll find, is you'll see people writing things like, name 7 plus, like that. OK? So what this means is, well see, it says here, since x and z contain the same information. So it's redundant, because you know that if you've got 3 on the atomic number, it's always going to be with you. OK? So you don't have to put both of them, usually. Sometimes if you really want to be specific, you'll go like that. OK? But that's really redundant, OK? So sometimes you'll see it this way, but not usually. Usually you'll see that, because those two pieces of information contain the same information. So what is this saying? This saying, well, lithium, we know the atomic number is 3. We know that the mass number is 7. So there's 7 subatomic particles in that nucleus, protons and neutrons. So we know there's 4 neutrons, right? Because we know every element of lithium has 3 protons. And we also know the charge of the ion. Things that are charged are called ions. But this charge of this ion is plus 4. The charge is 0 if the number of protons equals the number of electrons. So when I represented hydrogen here, I didn't put any charge of there, because it's 0, OK? So you don't usually put a 0 right there. But notice I put one there, because I had to indicate there was a charge, because I had lost. Everybody see that? OK, so based on the following information, what's the atomic number of chlorine? How do you find that? Where can you find that by looking at this representation? Yeah, what is it? It's 9. Why do you say that? Because it's here. You can look at it there, in the bottom left-hand corner. Or you could say, bam, it's flooring. So let's look up there and say it's the ninth element. So it's got to have 9 protons. Or the atomic number has to be 9. What's the mass number of flooring? Where will we find that? It's going to be 19. How do you know that? Well, you can look up there, and you can go to the table. But if you only have this representation to look at, what would you say? It's the top left number, right? How many protons, or how many neutrons does flooring 19 have? Hey, how'd you figure that out? 19 minus 9 equals 10. You get that? You get that? You get that? Bam, you guys are so good, you don't even have to worry about the rest of this chapter. OK, let's try this one. How many protons does this add in half? What's the name of this? Does anybody know the name of this add? Oron. Oron, yeah. It's like chemistry class, right? Boron. OK, so how many protons does boron have? Five protons. How many neutrons does boron 11 have? Six electrons. Now, what's the charge of this add? We've got positive negative 0. Why is it 0? Find the charge of this add, and if you were looking for it. What would it be? Is there anything there? No? So what does it mean? Neutral, OK? So let's try this again. What about this add, and what's the name of FV? Iron. Iron, yeah. OK, so what's the atomic number of iron? 26. How many protons does iron have? 26, good job. How many electrons does this iron add on have? 26, how do you know that? Because it's neutral, right? What if it was iron plus 2? How many electrons would it have? 24, right? 24, right? 24, because you're losing electrons to get positive numbers. Why do you, how come you lose electrons to get positive numbers? You can think of it that way. What about, think about it as either electrons, though. It's because electrons are negatively charged. So if you remove negatives, right, you get a positive. OK, so good job, guys. It's doing awesome. How many neutrons does this version have? Sorry for me to do that in my head. So notice, we talked about chlorine 35 and 37 a number of times today. So these, they're both chlorine atoms. Why are they both chlorine atoms? Because they have the same number of protons. Or what else could you call that? The atomic number. So they have the same atomic number or the same number of protons, right? OK, so, but notice they have different what? Max numbers, OK? But since they both have the same number of protons, they're both chlorine atoms. But they have a slightly different mass. So they have slightly different properties. What we call these types of atoms are isotopes of each other, OK? So they're different mass atoms that are the same type of atoms. And look up here. The mass number that you see here, this is actually the average mass number of chlorine that's found in nature, OK? And it's because, look, chlorine is 35.4527. It's because 66% of chlorine found in nature is 35 and 33% is 37, OK? So you're going to get some average that's closer to 35, OK? So notice the number of neutrons is different in the two chlorine atoms. You can look over this section of isotopes on your own. This is redundant. You can go ahead and check that out yourself. And we'll start on relative mass and things, OK? Typically, or especially, if you don't know how to read, OK?