hello i'm professor mccollum and this is zumdahl chapter 2 the beginning of general chemistry chem 25. this chapter is not a terribly long chapter the big part of it is nomenclature but we will go over some other things and i'm also going to do a little bit of an additional section at the end talking about math and some calculations we'll have to do in general chemistry so i generally use the ipad to write notes and use the slides that we typically use in class and i can write on both and i'll go back and forth to start though i think we'll just start with the slides because we're going to talk about some early history and some personalities and some people don't think the personalities are important but to me they're important for a couple reasons that i'll talk about and i hope you'll agree so when we talk about the early history of chemistry there's kind of a prehistory and early history and more modern history and so the prehistory would be when uh the greeks tried to explain why chemical changes occur and chemical reactions of course were known some of them are fire and [Music] brewing and distillation maybe creating some alcohol or wine um food going bad that kind of thing rust when people started using iron and bronze was a response to pure iron right because bronze doesn't rust but iron does um but for about 2000 years this mostly qualified as alchemy so alchemy had more of kind of a magic or mystical sense about it it was i don't even want to say pseudoscience it was some somewhat based in science but it wasn't always evidentiary sometimes it was wishful thinking or supposed thinking about things um during this time though some elements and we'll make this definition about what an element is some elements were discovered during this time and when we go through the periodic table nomenclature these will be the elements whose symbols are derived from latin callium potassium aurum gold natrium sodium and so on many mineral acids were also produced a mineral acid is something we would call now an oxo acid something like sulfuric acid h2so4 or nitric acid hno3 these would be considered mineral acids well nothing major change you know little discoveries here and there get some general knowledge passed down generation to generation until about the 16th or 1700s and here during the age of enlightenment and scientific inquiry was really started at least in the west we come to robert boyle robert boyle was the first kind of true chemist physicist and he performed and wrote down quantitative experiments and he developed the first definition of an element on an experimental basis an element is a compound a chemical thing that cannot be broken down into anything simpler so you could start with water and you break it down into two gases hydrogen and oxygen but these two separate gases hydrogen and oxygen cannot be broken down further so boyle quantified those as elements now one thing i'm doing here is i'm trading about a lot of modern convention like h2 and o2 and h2o but one thing you have to realize that this far back 16 1700s the idea of atoms or really molecules had not even come about yet so people described these things more quantitative it was oxygen it was hydrogen but nobody knew what the smallest piece of these things were and we'll talk about this we'll talk about this a little while so priestly in the 1700s was an important chemist because one of the things he did you see this is the priestly metal the american chemical society awards priestly medal each year to a accomplished experimentalist in chemistry and one of the things that he did is he collected oxygen over water and that's this apparatus over here we'll talk about this when we talk about gases in a little bit more detail but you can see this funny thing this over here is the oven or the the torch or the flame and then here there's water and whatever reaction is going on the oxygen is coming up bubbling up under the water and this picture i don't think is exactly accurate because the end of that apparatus where the oxygen comes out has to be under the water as we'll see later so i think the experiment that he did was mercuric oxide and again we'll use these modern known terms really before we define them and he heats this up we use the little triangle symbol for heat and he got mercury plus oxygen gas so the oxygen gas is what's driven off from the solid very actually very similar to the way that bubbles come out of a can of soda and then they're collected over water so let's talk a little bit about the fundamental laws that chemists use all the time and over here on the right we have a picture of lavassier and labossier was a chemist a scientist right before the french revolution this is kind of important and this is his wife madame lavassiere and some biographers think madame lavassiere was the brains of the operation but of course at this time unfortunately women were not taken seriously and did not get their due so she actually worked with him in the lab and she was probably uh as important to chemistry as lavoisier was himself you see he he's certainly think she's pretty important you can tell by the way he's looking at her lavoisier the lavassies i should say came up with the law of conservation of mass and in a chemical reaction mass is neither created nor destroyed that's the statement of the law conservation mass the way chemists tend to use this though is what i like to call the law of conservation of atoms this is the way chemists generally use the law of conservation of mass we know that if we count atoms and we balance atoms in a chemical reaction then we're conserving mass so that's really the way the chemists use the law of conservation of atoms about the same time we had proust and proud came up with the law of definite proportion and this sounds kind of silly but what the law of definite proportions says is that if you have some stuff a compound the proportion by mass of all the elements in the compound is the same okay so think about water uh ethyl alcohol co2 some other things right and again now that we understand and are comfortable with the idea of atoms these folks weren't we put things in atomic ratios ratios of atoms two hydrogen atoms to one oxygen they didn't know atoms so they had to put things in terms of mass we'll do some examples in a couple of minutes dalton we'll talk a lot about dalton dalton is an extremely important scientist in chemistry and dalton had the law of multiple proportions this is before his atomic theory the law of multiple portions this one's a little confusing when two elements form a series of compounds so you have to think about compounds that have the same elements like carbon monoxide and carbon dioxide and bicarbonate for example when two elements form a series of compounds the ratios of the masses of the second element that combine with one gram of the first element can always be reduced to small whole numbers in other words integers this one is a little confusing you need to think about two compounds and do kind of two ratios but we'll do some examples of this right so let's try that now let's think about illustrating each of these three fundamental laws with a chemical equation and or compounds and even though we haven't really talked about this or define them i think most of you at this point can come up with some compounds if you think about a little bit to illustrate this so what's how about the law of conservation of mass can you think of a of a chemical equation that illustrates the law of conservation of mass and remember probably we're going to do law of conservation of atoms well here's one i came up with and i drew drawing some pictures here i'm going to form water from hydrogen and oxygen and i'm going to use this uh well-known definition hydrogen is h2 and oxygen is o2 in elemental forms and water is h2o so then all i have to do is balance the atoms right i get h2 it occurs in pairs so i need two of these in order to get two water molecules and i need one oxygen molecule to get two water molecules because somehow don't know how somehow the oxygen molecule the diatomic molecule busts apart well how would we illustrate this in the law of conservation of mass well what's the mass and i'm going to again i'm going to use molar mass i think most of you know what molar mass is it's the representative compound mass of this two hydrogens while each hydrogen is two grams so if i have two hydrogen molecules i have four grams one oxygen molecule is 2 times the mass of oxygen 2 times 16 is 32 so we would say that 4 grams plus 32 grams equals 36 grams and that's how we might illustrate the law of conservation mass in a very simple way with a simple equation all right what about the law of definite proportion do you remember what the law of definite proportion is the law of definite proportion says any comp any sample of a given compound always has the same ratio mass to mass ratio of the elements in the compound so let's try to illustrate that i'm going to use water right so since we know water is h2o and we can use a little bit of our previous knowledge hydrogen weighs one right in relative terms and oxygen weighs 16 relative terms so there's two two masses or two grams of hydrogen for every 16 of oxygen in other words it's one part hydrogen to eight parts oxygen by mass we would say one to eight and a mass ratio and that's water that illustrates the law of definite proportion any sample of water that we get from anywhere anywhere in the universe it's going to have this mass proportion this mass ratio between hydrogen and oxygen and all we have to do is be able to maybe break these down into their elements to get that ratio okay the law of multiple proportions a little bit harder to illustrate right now we need two compounds at least two compounds to do this so let's see how this works a lot of multiple proportions i'm going to use hydrogen peroxide and water now you may know that hydrogen peroxide is h2o2 and water is h2o but again as i said it actually really helps illustrate these laws if we forget that we know what these chemical forms are remember all these three laws that we're talking about are happening before the idea of atoms just before the idea of atoms and well before they were accepted in any case okay so it turns out that hydrogen peroxide has one gram of hydrogen for every 16 grams of oxygen how did i figure that out well again if we go and use our formula we know we have 2 grams of hydrogen h2 and we have 2 times 16 or 32 grams of oxygen and you can see that 2 to 32 is the same as 1 to 16 in a mass to mass basis and we already did water right we should already hopefully from the previous slide we can recognize the fact that it was 1 to 8. so how does this work what this means is that the eight parts of oxygen to one part of hydrogen in water and the 16 parts of oxygen to one part hydrogen in hydrogen peroxide that ratio of 16 to 8 is itself its own integer right so we take the 16 and we take the a and we divide those by each other and we get 2 and that's an integer that illustrates the law of multiple proportions right so what this really means if you think about it you might have to think about a little bit it means that there's some fundamental particle of matter for each element and we just have to have some idea of what that fundamental particle is right so these three laws are going to naturally kind of progress into what dalton came up with it was dalton's atomic theory let's take a second and talk about john dalton because john dalton wasn't a scientist who worked at a university or for a king or or anything like that he was self-taught he was a school teacher in other words she taught like high school or something like that he would be a high school teacher these days but he was he was very smart and he thought about things and um in his in his spare time when he wasn't grading papers and came up with dalton's atomic theory it's very much outside the regular establishment this did not really help his theory because it took a long time for people to take him seriously okay don's atomic theory says let's think about an element there's got to be some fundamental small piece of this element that cannot be broken down any further and he's going to call those atoms this comes from the greek atmos which means tiny piece so now let's flush the solid the atoms of a given element are all identical and the atoms of different elements are different in some fundamental way that makes them a different element chemical compounds are formed when atoms from different elements get together in different combinations and a given compound always has the same relative numbers and types of atoms now this is important for a for a new theory it's important to integrate an existing theory or law this is the law of constant composition so what dalton has done is he's restated the law of constant composition in the context of his new theory chemical compounds are formed when atoms of different elements combine with each other in other words the law of conservation of mass and a given compound always has the same relative numbers and types of numbers this is really restating that other one right so that's against the law of constant composition so his new idea was really the the first one and the second one these other points integrate previously existing laws into his own atomic theory which helps establish it and helps people accept it so the question i have for you is when was dalton's atomic theory proved this says 1808 it took i got to tell you it took almost 100 years took to close to the end of the 1800s before the average chemist the average physicist accepted dalton's theory of atoms took a long long time and uh basically what had to happen is a lot of the established or older scientists had to die right because they got replaced by new younger scientists who are more accepting of new ideas that's one of the ways science progresses but when was it proved that's different from being accepted right so how do you prove a theory you need observations so let's talk about this a little bit because it turns out that really in a sense we haven't we didn't prove don's atomic theory until very recently where we can actually see atoms right so this is an example this is an example of a result from afm atomic force microscopy and the way this works is that you have a surface and you have this probe that has a very small narrow tip like this and it moves up and down over the surface and depending on the distance from the surface a current is produced so this is hooked up to some sort of small micro current and that current changes depending on how close something comes to this tip and you put the results through the computer to get something like this and these are atoms and i know you're saying they look like mountains they don't look like atoms but the trouble with the afm is is it cannot see what's happening underneath it just gives a signal that's proportional to the current so the signal looks like little mountains so what you're really seeing here is the atomic positions in other words this is a lot like flying over uh even the east bay on a foggy day and you can see the top of mount diablo poking through the the fog or the low clouds but you don't know what's going on underneath the clouds so if if this thing is really kind of circular all you really see is the very top of it this picture also illustrates some of the quantum mechanical effects of atoms you can see it's kind of all wavy and that this is actually the some sort of weird quantum mechanical interference we actually talked about quantum mechanics in second semester so here's another example this is more cartoony illustration of this of this afm tip it's only one or two atoms wide they have different atoms that conduct electricity and this what you see in the green red and blue is an actual image of a molecule and this is this is a cartoon a model of what molecule they use and you can see that kind of hexagonal structure coming out and so to me dalton's atomic theory has finally been proved in the last 10 15 20 years because we have these techniques such as afm and there's another technique that's very similar called stm that allows us to see these things these small things okay let's continue talking about these basic laws and they're important as i said because they provide context and it really helps if you put yourself in the shoes of these folks to think about what they knew what they didn't know so let's turn to more kind of experimental chemical reactions we had the work of gila sac and avogadro and yes it's that avogadro these guys did experiments with gases now gases are kind of hard to work with you can't weigh them because they don't stay on the balance of a scale really the only way that you can measure the gases is through its volume and its pressure and the pressure pressure is harder than volume right you can have a volume like a balloon or something with a movable lid like a piston and you can measure volume that way but pressure requires kind of an outside instrument so these folks used volumes to measure things so what gay lesac found was that if you keep the temperature and pressure constant that volumes were proportional in the same way that the law of multiple proportions and law of constant proportions worked in other words d less sac would say that that two liters of hydrogen and again i'm just gonna use the name because they did not real this is right around the time atomic theory was being developed and people just didn't get it yet plus one liter of oxygen if it fully reacted you got two liters of water vapor in other words gaseous water so if you scroll back to what we did before and we use regular chemical equations with atoms and compounds that we're used to these days you can see that the proportion is two hydrogen one oxygen and two water just the same of this in other words volumes of gases are proportional to amount consistently and avogadro flushes out a little bit he said at the same temperature and pressure equal volumes of different gases contain the same number of particles so avogadro said that volume is proportional that's a little backwards number is proportional to volume if you hold temperature and pressure constant so the volume of the gas is fundamentally determined by how many gas particles are in that volume and this is this is very important and we will come back as when we talk about gases and use this to simplify our calculations a great deal so let's look at these results a little bit right as i said before you could say two volumes of hydrogen you might want to turn this an natural unit two liters of hydrogen plus one liter of oxygen will give you two liters of gaseous water right what i want to do now is think a little bit about the idea of atoms and chemical formulas because remember these folks didn't really understand atoms or the idea hadn't really been spread around so this idea of fundamental particles was being banded about and people needed to test to see how this worked so what i want you to do right now is forget all you know about hydrogen being h2 and oxygen being o2 and let's play around with that let's say okay let's let's say that there are atoms right oxygens and hydrogen atoms hydrogen and oxygen and somehow water is some combination of these x and y x can be one or two or ten and why two we don't know what these are how can we use this to help understand formula well let's think about this what if you just say that hydrogen naturally occurring hydrogen elemental hydrogen is hydrogen atoms well according to gila sac and avogadro that meant that these two liters of hydrogen are proportional to two amounts of hydrogen some number amount right but it's proportional so the two is the important part so if we just have hydrogen atoms being hydrogen or elemental hydrogen then i'll write this as two h and likewise for oxygen if oxygen just exists as oxygen atoms in its natural elemental form then i just have one o well this is going to form two equivalent molecules of water so how can i get two volumes or two molecules two compounds of water from two h's and one o i can't right because i can't break up one oxygen atom into two pieces that doesn't work so it this doesn't really work for the elemental formula of hydrogen oxygen let's look at another one what if we fix this by saying okay hydrogen is just h but what if oxygen is diatomic right it consists of two oxygen atoms stuck together somehow well in this case i could get two identical molecules of water one hydrogen and one of those two oxygen i could have ho if that's true then waters formula and i'm sorry this thing keeps popping up to kind of cover up what we're doing each water molecule would therefore have the formula h o right okay well what we do know now is that both hydrogen and oxygen are diatomic molecules so 2h2 and 2o2 still allows us to get two identical molecules of water in this case the formula is h2o right so the problem at this time 1800s was how can i make clever experiments to confirm or tell me what the actual molecular formula is whether it's an element or a compound how many atoms are and this is a problem that they had to solve and we take that for granted now another example of of gay lussac's experiments was hydrogen and chlorine and hydrogen chloride right so again you could run through this h cl to well you can't you can't really get two things if both of these are monatomic if hydrogen is h2 but chlorine cl this also doesn't work because we need two molecules but if it's h2 and cl2 then we can get two hcl and it does work right so this is one way that you can use these experimental results one volume of hydrogen one volume of chlorine gives you two volumes of the resultant gas to kind of confirm what the makeup of these compounds are so here's the water the water picture we've already talked about this okay so our next step is to move past dalton's atomic theory and start thinking about a little bit more complicated things and what i'm going to have to do now is i'm going to have to start writing a few notes okay so at this point let's assume that we accept this atomic theory that so we have we have an atom for a particular element we have an atom and let's just for to be a little bit different let's say that we have magnesium so we've gotten a magnesium atom the next question that people started asking is well what's a magnesium atom made up of magnesium atom is fundamentally magnesium but there's got to be something inside that affects the properties of magnesium differently from say chlorine well jj thompson was one of these experimentalists who worked on this and i want to take a second and say throughout this lecture i've been saying guys when i'm talking about scientists and that's accurate mostly it was men doing this is very rare for a woman to to get credit for anything at the very least we talked about mana morphosia in fact marie curie was probably the first female scientist at least in the west at least in kind of the modern age that was taken seriously and probably she still you know caught a lot of flack and and wasn't really um taken seriously by everybody um and i say this because that's a problem you know there's talented people in all walks of life and uh as i'm talking about all these mostly male scientists um if it kind of um gets your dander up a little bit that's good anybody you know anybody who has the capability should be able to do science and these days it's really changed not quite as good as it should be but we're getting there okay so thompson this says he postulated the existence of negatively charged particles this did not come out of thin air and we'll see in the next slide so what he what he did is he took a sample say of magnesium and he applied a very strong electric field to this right and we represent that by symbols like this basically means a very strong battery and this creates an electric potential and so this makes this end very strongly positively charged and if there's any negative particles they will shoot across this way so that's what he did with magnesium okay and it turns out that experimentally there are ways to determine the charge to mass ratio sometimes we call that m over z mass over charge this will come back a little bit later in a little bit different manner okay so let's draw our cartoon again so if we take magnesium and we get a particle that comes out that's negatively charged that means the resulting atom that's left behind has a positive one charge so posturing the idea of these electrons coming off magnesium atom not only says that these little negative particles come off it it says that what's left behind must be positively charged because atoms start out as being neutral okay here's here's what a cathode ray tube comes up we have a apparatus like this back in the electron but i can't show it to you here at home here's the metal electrode and here's another metal electrode and this is a source of electrical potential like i said very strong battery or so on that creates a high electric potential here's the positive end and what happens is negative particles shoot across here and this has a partially evacuated glass tube well what happens is these little negative particles hit some of the gas molecules and it causes little flashes you can really emphasize this by putting a screen a phosphorescent screen that will glow when hit by charged particles and you arrange it across where this beam where this beam will go just so it kind of the beam kind of skips against it kind of like rocks skipping on water if you if you skip rocks on water so you have to move this just right until you get the glow and then you can see the glow as we can see in this left-hand picture that's thompson so thompson is associated with the identity and characterization of the electron well could figure out the relative charge you could call the relative charge of the electron minus one just for convenience we don't know exactly what it is let's just call it minus one and he figured out the charge to mass ratio but what he could not figure out absolutely was either the charge or the mass it's kind of weird but it was it was a result of the types of experiments we were doing well milliken was another experimentalist and he um took oil drops and used like an atomizer which is like an old-fashioned perfume bottle to create a fine mist of oil and then he shot x-rays at the oil which ejected electrons and then he turned on an electric field to make the oil drops hover and i won't go into the details here but that allowed him to calculate the charge and the mass of these electrons so he calculated both the charge and the mass of the electron now i say these slides go into great detail about what the actual mass is what the actual charges but to me it's a little bit it helps understanding a little bit more to realize that those numbers are so small they're meaningless right and we we're going to eventually use these numbers but it's much easier just to think about relative charge so if we have a relative charge of minus 1 this turns out to be minus 1.609 times 10 to the minus 19 coulombs of charge what is a coulomb we'll get into that and then we have a plus one relative plus one charge would be the same charge and then we can also write m e for the mass of the electron and this is 9.11 times 10 to the minus 31 kilograms but i don't want you to memorize this what i want you to think about are what are the relative masses and charges well it turns out that if we have a magnesium atom and we have an electron the mass of the electron is essentially zero compared to the magnesium atom right and here we can compare the the charges both in an absolute and a relative sense but at this point it's the relative part the simple charge or the simple mass that's actually more useful to us beckerell was another scientist right around 1900 just before 1900 and he actually inspired marie curie and the curies her husband to um he discovered radioactivity and what he what he had done is he had put some uranium in his drawer with some photographic paper he just happened to put him in the same drawer and later on when we when he went to get the photographic paper he noticed it had been exposed but of course the drawer is dark so how did this photographic paper get exposed it got exposed because the other material in the drawer the uranium radioactively exposed this film and when we talk about nuclear chemistry we'll talk about radioactivity in a little bit more detail but we will say that the three types of radioactive radioactive emission exists gamma rays which is essentially just energy so if you have a an atom or something that's very high energy it'll spit out gamma rays which are high energy light beta particles all the beta particles is an electron that carries away kinetic energy right it's a fast electron and alpha particles are uh turns out it's a it's a helium plus two ion so it's kind of a massive particle as radioactivity goes so in radioactive processes you have excess energy kinetic energy can carry this away you if you have excess energy it can be carried away as light energy or you can kind of have a mass mismatch in other words for some reason the mass is too heavy or too light to be stable in which case you might get these alpha particles being emitted so next what we want to start thinking about is the nuclear atom so as i said people were starting to wonder about what's inside the atom what's the structure of an atom right just because you drive a car around doesn't mean you don't need to know a little bit about how it runs in case you break down right maybe it needs an oil change or a or a belt or something like that so you need to go a little bit deeper than just the outside knowledge to be able to to work with the stuff so rutherford had this famous experiment which we're going to talk about a little bit but the nuclear atom nucleus or nuclear means small important or hard core um and that's exactly what the nuclear atom was well before the nuclear atom model that rutherford came up with people really didn't know um what an atom was one of the models that had gone around was the so-called plum pudding model these days in the states we really don't know what plum pudding is do you really know what foam pudding is but i'll tell you what i know what a blueberry muffin is so i like to think about this as the blueberry muffin model and the idea behind the blueberry muffin model is is well people accepted or understood that electrons could come out of atoms right so what we're going to do in this model is say okay we've got these atoms inside or i'm sorry the electrons inside the atom like blueberries in the blueberry muffin right so the electrons which are particles not very massive but they're particles like blueberries can be ejected and then what's left behind is the delicious muffin cake-like materials left behind but it now has a positive charge right and then there's some uniform positive charge and you can think about this as batter or kate right that kind of sits behind but this is kind of uniformly spread throughout the atom that's the plum pudding model and this was really the only model people had uh so rutherford said well i want to test to see if i can prove the plum pudding model or disprove it and he came up with i guess i don't have a cartoon of this one he came up with an experiment where he took some gold foil and there's an important property of gold it's very malleable you can take a teeny tiny piece of gold and you can pound it into a sheet you can take a fingernail pinky fingernail size piece of gold put it between two pieces of leather and pound it into a sheet so it's about the whole size of a sheet of paper and this is only one or two atoms thick right so what we have is we have the foil now there's only one or two atoms thick let's assume it's one atom thick so what rutherford is going to do is he's going to shoot alpha particles remember alpha particles are charged particles and they're relatively massive it turns out as i said they're helium nuclei right so this is like shooting uh alpha particle bb at some bricks or something like that right so he's going to shoot these alpha particles at this gold foil so now think about what happens if a small positively charged bb hits the blueberry muffin model well if it has to move through the cake maybe it's going to slow down right come out the other side slower than it went in if it hits an electron maybe it's just going to stop because the opposite charges are going to cancel each other right maybe they'll kick an electron out right so these are some of the things that might happen well rutherford put a detector all the way around his gold foil like this and when he shot the alpha particles he found that some of them went through some of them kind of bent up like this and once in a while not very often but once in a while they bounce straight back and there's a very famous uh account that he had that he said he couldn't have been more surprised that if he had shot a cannon at a sheet of tissue paper and the cannonball ended up back in his lap you just didn't expect this to happen at all so most of the alpha particles went straight through or bent a little bit but once in a while he had a bounce back it was very very strange so he actually took almost two years thinking about this to figure out what was responsible for this well what he came up with was the nuclear atom and the nuclear atom schematically is like this so all of the mass is in the nucleus the center all of the space since the nucleus is not much of the space all the space is taken up by the electrons moving around somehow and because electrons are negatively charged if you put another atom here this is why atoms can't move on top of each other in other words this is why you get this sound that's electrons bouncing off each other they can't occupy the same space so the hardness of an atom is due to the electrons right and what he came up with is the electron but the nucleus also contains all the positive charge that's left over when you take the electrons away so the nucleus comes up there is made up of protons which are going to call p plus and neutrons which i'm going to call n0 for neutral things and these things are the massive particles in the nucleus so let's look at some other characteristics because the nucleus is really small and has all the mass it's extremely dense extremely dense um the overall density of an atom comes from this big empty space that the electrons occupy and it's kind of hard to do the electrons move do they bounce around i'm not saying right now they just take up this space somehow so here's a cartoon of the idea of nuclear atom and it gives you the relative sizes this is in centimeters so this picture says the nucleus is about 10 to the minus 13 centimeters in diameter okay that's 10 to the minus 14 i'm sorry 10 to the minus 15 i have to get my powers of 10 right meters in diameter and the overall atomic diameter is about 10 to the minus 10 meters if you take the ratio of this this is a ratio about 10 to the five in other words the whole atom is 10 to the 5 or 100 000 times larger than the nucleus and i calculated this once if you put a marble at the center of campus if you put a marble at the center of campus then the whole rest of our campus would be the atom and the marble would be the nucleus that gives you kind of a general idea of the size difference here and remember all the mass is in the nucleus well if we think about rutherford's experiment and why things happen the way they did is that if we take our alpha particles most of the time they just fly through empty space the electrons are moving around so fast or very diffuse but they don't really offer much resistance it is like the tissue paper that rutherford referred to well once in a while an alpha particle will get close to the nucleus and it kind of gets deflected like this because remember the alpha particle is positively charged and the nucleus contains all the positive charge too so these things will repel each other so if the alpha particle gets kind of close to the nucleus it bends all right and then the most interesting thing is if the alpha particle makes a direct hit on the nucleus very rare right because remember the nucleus is 100 000 times smaller than the whole rest of the atom so it wouldn't be like exactly a hundred thousand times out of or one time out of a hundred thousand times it would be something it's kind of complicated complicated to calculate that but it would be very rare right so that kind of describes that's how rutherford came up with a nuclear atom because he applied mathematical statistics to his his results alright so now we have elements and elements are made up of small pieces called atoms and atoms are made up of protons neutrons and electrons protons and neutrons exist at the center of the atom and contain all of the mass but almost none of the space the electrons make up most of the space so this doesn't fully define the possibility of atoms because we can have different combinations of each of these things the only thing that really governs this overall is overall they must be neutral so what that means is the number of protons equals the number of electrons well it turns out we'll see this in more detail but it turns out the number of protons determines what element it is and it turns out the electrons determine the chemistry so the identity of the element is determined by the number of protons but the chemistry of the element whether singly or in compounds is determined by the electrons this is a little bit weird but it's not inconsistent or it's not really opposing these two statements don't really oppose each other but notice this doesn't say anything about the number of neutrons because it turns out the number of neutrons may vary and as long as the number of protons remains the same while the neutrons are varying within different atoms the element is the same the mass is just different we call this isotopes so isotopes are atoms of a particular element so they have the same z i'm sorry they have the same number of protons but the number of neutrons varies right and what i forgot to say is that we have this term the atomic number the atomic number which is represented by z is the number of protons in an element okay so isotopes the number of neutrons can vary but isotopes of the same element must have the same z and then neutral species also has the same have the same number of electrons it's a little bit confusing right so here's an example sodium right the fact that you have sodium remember sodium's atomic i'm sorry sodium's symbol is n a we'll talk about this a little while for sodium z is 11. so as long as z is 11 in other words there's 11 protons it will be sodium but there are two isotopes of sodium sodium with 12 neutrons and sodium with 13 neutrons well in order to kind of account for this and keep track of this more easily we have what's called what's known as an isotopic symbol this is the symbol right we're going to represent this by an x just kind of a generic symbol and we're going to put on top we're going to put a and on the bottom we're going to put z so the atomic number goes as a pre-subscript but what is this a a is known as the mass number now it's important to realize this is not the mass it's an integer and it's the number of protons plus the number of neutrons so the mass number is an integer the atomic number is also an integer so in our case of sodium we would have 23 over 11 sodium 24 over 11 sodium the first one we call sodium 23 and the second one we call sodium 24 that's how we refer to them and it should be said that the 11 part is really redundant right because it turns out if you know z is 11 it's sodium therefore the symbol is n a if it's n a the z is 11. so those things really tell you the same information so very often in isotopic symbols they're left off like this so here's review on top goes the mass number the bottom goes the atomic number and then you use the symbol in place of the x once you know it this does give you a way to decode back and forth too using the z and the element symbol so what this also means right is that a equals z plus p i'm sorry z plus n let's write it that way because in some sense the z and the p mean the same thing so the number of neutrons equals a minus z this is usually what you do to figure out the number of neutrons so if we have a certain isotope has 23 protons 28 neutrons the mass number a is going to be the sum of these is going to be 51. so let's put a 51 here the atomic number is 23 and now we can identify what the element is using our periodic table we just look for the 23 in the z position and we find out that this is vanadium okay let's talk very briefly now about chemical bonds we're going to talk very briefly we talk about chemical bonding in great detail in chem 27 but in chem 25 we're just going to do enough to get us going okay remember what i said that the chemical identity of the element is determined by the number of protons the atomic number z but the chemistry is determined by the electrons so this is going to be an example of that chemical bonds are part of chemistry and the electrons are really responsible for chemical bonds so it turns out that bonds form between atoms when electrons are shared and once you start sharing multiple atoms together you get a molecule so the first kind of bond that we're going to talk about very briefly is a covalent bond so for our purposes at this point covalent is going to mean shared bond so here's a very simple way that we get a chemical bond let's take two hydrogen atoms right we're gonna take their electrons away there's one electron per hydrogen atom i'm going to put those there there's two protons collectively so what i'm going to do is i'm going to put one proton here and one proton here in space and then i'm going to put the electrons in between them this proton over here on the right is going to kind of be attracted to those electrons this proton is going to be kind of attracted to those electrons so the two nuclei are held together by their mutual attraction for the electrons well this is a lot like if you hang out with a bunch of friends i had a friend in uh high school was my best friend he had a friend who he really liked and i didn't really like that much so you can think about me and this other friend as the protons that we don't really have a tendency to hang out together right we're both positively charged so we repel each other but since we were such good friends with the third friend we all hung out together because we were mutually attracted to him right so that's kind of a funny way to describe it but uh we have one other way cartoon way of showing this right if we have the two nuclei like this sorry for that interruption and then the electrons are kind of like this in between then these positive nuclei are attracted to a common center as i said this will be a very brief overview of different types of bonding the other main type of bonding and we're going to show just enough to show you that electrons are very important in all kinds of bonding is an ionic bond an ionic bond is purely electric from charges it comes from the atoms gaining physical charge transfer an electron gets transferred and this forms an ion the examples i'm going to use are going to be monatomic as opposed to polyatomic so uh the very simplest example is generally given is something like sodium chloride what essentially happens is that the sodium becomes sodium ion it loses an electron and then cl2 will become two cl and then the electron maybe from sodium from anything will give you chloride so what happens here is the negative chloride ion and the positive sodium ion are attracted electrically but this comes from an electron transfer so each species is actually charged now let's go back and contrast this to a covalent bond where the electrons are shared we could almost call covalent or shared electron a kind of a blue spread between the nuclei but an ionic bonding it's more physical charge separation and so you can see in both cases the electrons are very important but in the first case the electrons are shared like glue and in the second case an ionic bond an electron is actually transferred from one species to another forming ions the only other thing we need to go over here is that a positive ion is a cation and a negative ion like chloride is an anion now when we get into nomenclature naming we'll you'll notice how the positive ion retains its elemental name sodium becomes sodium ion but chlorine becomes chloride ion so there's some conjugation going here and this will actually help us in naming in nomenclature all right so let's do a quick review if we have an isotope we're going to call x plus it has 54 electrons and 78 neutrons 54 electrons 78 neutrons well if we look at this we've lost one electron leaving 54 so it had 55 electrons originally this means when it was neutral so when it was neutral that means there were also 55 protons so we can now say that this is x with a 55 down here and a plus up here well now we know the mass number is going to be the protons plus the neutrons this is going to be 55 plus the 78. this is 133. so now we can write the full isotopic symbol 133 55 x plus so the mass number is 133. what's the atomic number well we have to look up in the periodic table to figure out what the atomic number corresponding to 55 is and using any periodic table that's handy we can find out that atomic number 30 or 55 corresponds to cesium in other words this is cesium plus 133. now just a note on that plus never assume a charge on an isotopic symbol species very often the charge is left off but if it really matters it's going to be put on there this is a little bit confusing but it turns out most of the time when we're dealing with isotopic symbols we're doing nuclear chemistry it turns out the charge doesn't matter so much sounds weird but it doesn't matter so much because it's easy to account for it and when we're working with more ionic compounds then we usually don't care about isotopes too much in other words the chemistry doesn't change just because the mass changes so it turns out not to be as big a problem as you might imagine all right so as we begin our overview of nomenclature this is really the big topic in this chapter let's start by just having an overview of the periodic table itself okay the periodic table is generally grouped into two main categories metals and nonmetals and it turns out there's a lot more metals than nonmetals and the border between the metals and the nonmetals are known as metalloids just remember this when we get to the table so that's kind of a grosser general general classification we have the metals over here and then non-metals over here and then the border elements are called metalloids we also group these into columns or families because it turns out that elements that are in the same column or family in the periodic table behave very similarly in a chemical sense and we'll see this too so we have groups or families vertically and horizontally we call these periods so here's one version of a periodic table and there's a lot going on here and you see what you can see here is this black order so this is the border between metals and nonmetals so over here we have metals and over here we have nonmetals and it turns out that things touching the border are going to be mostly not entirely these are going to be metalloids on this border area okay and the the families or columns or groups in the periodic table are just numbered 1 to 18. you can see this 1a 2a business this is kind of an old classification and now officially we just number these 1 to 18. so within these classifications we also have specific or family names so this first column is known as the alkali metals the second column is known as the alkaline earth metals this big group in the middle a 40 transition metals so transition metals are a big chemical group there's some more metals down here there's the metalloids here the metalloids are gallium germanium arsenic antimony tellurium polonium and who did i forget i forgot silicon these are the metalloids don't worry we'll learn these in more specific detail this last second to last column these are the halogens fluorine chlorine bromine iodine ascentine and uus we're not going to worry about these last two too much we almost never see them and the very last column in the periodic table are known as the noble gases noble gases are unreactive they tend not to form compounds at all and eventually at the end in the second semester we'll really explore why this is in terms of the chemistry these other two groups the lonantides and the actinides actually occur inside here we'll talk about those in more detail when we need to so let's look at the families it turns out that these certain families in the periodic table tend to have certain charges so the alkali metals tend to have a plus one charge when they're in when they're ions the alkaline earth metals group two tend to have a plus two charge when they are ions the halogens remember the second to the last column tend to be minus one and the noble gases are neutral so if we go back if we go back and write on this then let me pick a good color alkaline metals plus one alkaline earth metals plus two halogens minus one noble gas is zero we'll also be able to make some general charge statements about these different species i'm circling more or less but the pattern continues in other words some of these are minus two minus three minus four and so on that there's trends that we will notice all right so let's talk now about actual chemical nomenclature let's kind of get into the trenches and figure out how to name these things we're going to name it we're going to go through a number of different classifications binary compounds are going to be first that means it contains two elements one's going to be a metal we're going to talk about binary ionic one's a metal and the other one is going to be there for a non-metal binary covalent compounds are going to be a compound where there's no metal and we're going to learn how to name these they're fundamentally different so the first kind of binary ionic or binary compounds we're going to talk about are binary ionic compounds type 1 you can think about these as being simple type 1 are simple binary ionic compounds this is going to be a metal plus a non-metal now as we saw with sodium a little while ago the metal is going to be considered to be the cation and remember a cation retains its elemental name and it's just called an ion the non-metal is going to be the anion and naming anions is a little bit more complicated than non-metals but it's not too hard so it turns out type 1 compounds follow this simple rule the cation is always named first in the anion second so in other words if we have a compound of sodium metal and chlorine it's always going to be named or arranged with the metal part first sodium first the monatomic cation takes this name from the name of the parent element sodium if it was all by itself we would call it sodium ion but this is not this is going to be a neutral compound and the anion is going to be named by taking the root of the element name and we're going to add ide to the ending so in your head you should think chlorine then chlor for the root then chloride so when we're finished we put this all together sodium chloride okay let's do another simple binary compound that's a little bit more complicated now what's implied here and it's very important is overall neutral compound in other words the goal here is to make the overall compound neutral and what we have is we have sodium ion and chloride ion we put them together plus one minus one makes it neutral on a one to one basis so what we're going to have to do is we're going to have to go back to this or maybe just the periodic table when you can remember the order plus one first column plus two second column and so on and this is going to be kind of our initial basis for naming these ionic compounds so let's see how that works with what if we have a compound made up of magnesium and iodide okay i'm sorry magnesium and iodine well magnesium is going to become the positive ion but if we go back to this magnesium is an alkaline earth metal so this is a two plus an iodine is a halogen so it becomes a minus one so we need to combine these two together to make it neutral we need two negative iodines with one positive magnesium so the compound is going to be mgi2 and this is going to be magnesium iodide notice we're not specifying a mouse so if you ever hear a numerical in an ionic compound its name that numerical is actually going to tell us something different than how many of these ions exist together this is a little weird but it will make sense if you practice a little bit all right so we never specify amount here's some examples kcl potassium chloride mgbr2 magnesium bromide similar to magnesium iodide and cao calcium oxide so in cao we have an example where we have calcium which is two plus when it's charged and oxide which is two minus when it's charged and you end up with a one-to-one correspondence calcium oxide so let's go back to the periodic table because i i said the pattern is kind of followed for these other things but i didn't specify that the pattern c n o f p s c l s e v r so this is a schematic of those last few rows and let me add the noble gases n e a ar kr well we know the noble gases are zero charged and we know the halogens are minus one charge so this pattern keeps going oxygen when it's an ion is usually o2 minus sulfur is usually s2 minus selenium is usually s2 minus nitrogen if it's in a compound with a metal is going to be n 3 minus phosphorus is going to be p3 minus and finally carbon is going to be c4 minus all right so we saw the example up here of the oxide right but what if we had mg se right well first of all remember it's usually going to be getting the name from the formula or the formula from the name so let's get the name from the formula that's usually a little bit easier we just have to remember not to use numerics magnesium selenide right because it's one of these guys it's a minus two magnesium's plus two so it's one to one this is all consistent let's go the other way let's try to get the formula from a name what if we had sodium phosphide well phos comes from phosphorus so this is p and the cation is going to be sodium and sodium is always sodium plus the cations are going to have a specific charge always all right well sodium is sodium plus what is phosphide we go over zero one two three here's phosphide phosphorus it's phosphide so this is p3 minus so the formula for sodium phosphide is na3p sometimes what people do is kind of do a crisscross applesauce thing where they take the charge from one and make it the subscript on the other and then you just have to reduce fractions let me give you an example of that with one we've already seen calcium two plus oxide 2 minus if we go crisscross applesauce we get ca2o2 but then what we're going to do is we're going to reduce this to the lowest ratio which is then cao that's type 1 compounds type 1 compounds we have a simple cation and atomic cation we have a simple anion that gets an ide ending and that's a type 1 binary ionic compound now there is type 2 type 2 or what most people would say are complicated what we're going to do here is we're going to use transition metals transition metals have more than one charge state almost all of them have more than one charge state or we call this an oxidation state so this makes it a little bit more complicated so what's the strategy here the strategy is going to be we're going to use the anion anions always have a definite charge so we're going to use the anion to determine the charge in the cation and that's going to help us name it and i have to say i just realized a few minutes ago i said that the cations always have a definite charge they really don't transition metals don't necessarily have a definite charge so you have to use the anion i meant to say anions always have a definite charge but there's many more ways that we can get anions as you'll see okay so we find the charge of the cation the charge of the cation equals a roman numeral when we write down the name or just the number when it's spoken and overall again we want a neutral compound okay so let's see how this works let's start with a really simple anion what if we have um and usually it's harder to go from the formula to the name than the other way around with transition metal compounds so um let's take cri3 okay well what's the strategy first we know that the iodine is really iodide and there's three of them so that gives us a minus three charge that means the cr is plus three in other words cr3 plus and i minus and you can see now where it come where the cri3 comes from but to name this species what we have to do is we have to specify the charge on the chromium with the roman numeral when we write it down we're just saying a three when it's spoken so let's write it down chromium three we use roman numeral iodide chromium three iodide so when you say this you just say chromium i forgot that r the h sorry you don't say chromium roman numeral three iodide that's a mouthful just say chromium three iodide okay here's some other examples cubr the way you name this dissected bromine is always minus one that means the copper has to be plus one that means it's copper one bromide sulfide in a monatomic anion is always s2 minus that means the iron is two plus that means it's iron two sulfide right remember that number specifies the charge in the transition metal not the amount that we have finally we have pvo2 there's two oxygens which are really oxides an ionic compound each one's a minus two so two times minus two is minus four that means the lead the pb has to be plus four so it's lead for oxide so now there's a complication the complication is polyatomic anions the bad news is there's many many many polyatomic anions the good news is a the naming is mostly systematic there's patterns that we can depend on and b their definite charge so you have to memorize some of them but the charge is definite so that allows you to puzzle out transition metal charges in type 2 compounds so what are some of the common polyatomic anions o h minus hydroxide cn minus cyanide no3 minus nitrate so4 2 minus sulfate and so on well remember what i told you when we first did anions is that monatomic anions get an ide ending well oh and cn are not monatomic but it turns out that the o and the h are so tightly bound to each other in hydroxide and the c and the n are so tightly bound together in cyanide that they're treated as a monatomic anion this is kind of a little bit screwy but that's the rationalization that chemists give for giving these identities and they've been called this for many many many years it's too late to go back now okay so ide does indeed mean monatomic anion so that helps you contrast between sulfate and sulfide right sulfide means it's just sulfur 2 minus sulfate is so4 2 minus so ate and ite mean polyatomic anion in the same way that ide means monatomic anion so there's a table in your textbook table 2.5 you should memorize these polyatomic anion species but the good news is that there's patterns so let's take a minute right now and talk about these these patterns a little bit right for monotonic anions it's pretty simple right you just follow that pattern the periodic table minus one for the halogens minus two for oxygen and sulfur oxide sulfide minus three for nitrogen and phosphorus nitride phosphide and so on well let's look at two common anions and see how this pattern works the first one is called nitrate the second one is called nitrite so taking these as an example we have these oxo anions very common polyatomic anions some nonmetal plus oxygen plus some charge that's negative well we can treat the eight as meaning more in other words more oxygens and we can treat the ite as fewer in other words fewer oxygens and we have to memorize that these are both -1 charges but these anions are named by taking the root of the non-oxygen element knight it's actually nitr with the r and you get the eight for more oxygens three and the eight for fewer this pattern is repeated for sulfate and sulfite now if you have just a single oxoan ion it gets the eight right an example of this is co32 minus this is carbonate it turns out there is no carbonite there is no co2 two minus anion there's no carbonite it's a mythical species before we get to the more complicated polyatomic oxoanions let's interject here with positive polyatomics it turns out there's many many many of these but we're only going to memorize two and we're going to try to see the pattern later nh4 plus is ammonium h3o plus is hydronium so ium means polyatomic cation and the most common way that polyatomic cations are formed is by putting a proton h plus on a nitrogen-containing compound so if you have n2 h5 plus this is going to be something ium it's going to be the name of whatever that neutral molecule is plus iu n so this is hydrazonium because this comes from hydrazine okay so anytime you see an ium in a name that's going to be a polyatomic cation probably because of the nitrogen the nitrogen is going to take a proton we'll talk about this a little bit more when we do acid-base chemistry all right let's look at the halo oxo anions now halo oxoanions this is a halogen like chlorine plus some oxygen the good news is all of these are -1 in charge but let's let's use an example of bromine to see how the name is it turns out you can have bro minus bro two minus bro3 minus and bro4 minus the key to understanding how these work is by starting in the middle right and we're going to apply the rule that we just said the ite and the eight rule to the two middle species so let's start with bro3 minus this is going to be brome the root of that non-oxygen element and it has more oxygen so this is going to be called bromate okay bro2 minus now it has fewer oxygens than the bromate so this is bromide and the idea here now is we're going to say even smaller and even more okay so smaller even smaller means hypo the word hypo means really small so it turns out the bro minus is called hypo and we use the prefix per to mean even more per bromate okay so for a long time when i was learning the names for the first 10 years i did this in my head when i was a young chemist i always started with the o2 version and the o3 version and named the bromide bromate and then went smaller with the hypo and more per so it's a little bit time consuming might have taken four microseconds in my head rather than one microsecond but after a little bit of practice it comes to you naturally and i would say that this pattern applies to all the halogens and many other cases also that you might run into okay now there are some other anions we have to worry about most noted notably the oxygen cases okay let's say that 99 of anion oxygens are oxide o2 minus so most of the time when you see oxygen and ionic compound you're going to assume it's oxide o2 minus once in a while though there's others there's peroxide o2 two minus and there's also superoxide o2 minus okay the good news is that peroxide and superoxide are almost always paired with potassium or sodium okay so you train yourself that if you ever see a compound that only has potassium and oxygen only has sodium and oxygen you very very carefully dissect it let me give you an example so here's different ways we can combine sodium and oxygen but in every case you can fall back on the fact that it's sodium plus sodium plus is the simplest way to start this right in this case we get o2 minus so that's superoxide so the first compound is potassium superoxide the second case we have o2 2 minus so the second one is sodium peroxide and the last case is just sodium oxide so just be careful if you see oxygen paired with sodium or potassium take a little bit of extra time and you'll be able to figure out what it is okay the next thing we need to talk about are type 3 compounds or compounds that are purely covalent they have no metals in them we're going to focus on binary covalent compounds in other words compounds that have two elements in them we'll extend this a little bit because once we learn how to do it with with two elements it's really not much harder to do it with with more and there'll be some other examples one of the things we have to get used to is we want these compounds we want the nomenclature of covalent compounds to sound the same as ionic compounds that we've already talked about we don't want them to sound different or funny so we're gonna name these in order in other words the order that they occur in the formula is the order that we name them and the second or last element in the compound gets an ide ending so we name it as if it were an anion with an ide ending now unlike uh ionic compounds we cannot use the charge and the fact that the compound is neutral to figure out the combinations of the the two species present so for covalent compounds we need to designate both in the element and how many atoms of that element are there and we just have standard prefixes for this mono die try all the way up to deca although it's pretty rare to see things above six or so and we never use the mono prefix as it occurs first let's go through a few examples some of these you'll know and it'll reinforce these rules so for example co and co2 very similar compounds named a little bit differently but they are covalent compounds in the first case we named this carbon monoxide not monocarbon monoxide but carbon monoxide the second case we have two oxygen so this is carbon dioxide now notice what we've done here in the monoxide is we've kind of combined the second o and mono with the o and oxides so sounds a little bit awkward to say mono oxide so it's just contracted into monoxide other examples pf5 this would be phosphorus pent penta fluoride and we might have n2o6 dinitrogen hex oxide and here's some other examples they're very similar sulfur hexafluoride dinitrogen tetroxide and so on so here's another example of a contraction tetra oxide is usually contracted to tetroxide so we try not to put two vowels together in the names so these type three compounds overall are pretty pretty straightforward now the next set of species we need to talk about let me burn through these are acids now the characteristic of an acid is h plus a proton or hydrogen ion plus an anion so in a way these are like ionic compounds sometimes called salts ionic compounds where the metal is replaced with hydrogen ion and an anion if you think about it all acids have h hydrogen ions sitting out front so it's like h something so you cannot really name an acid on the bases of the hydrogen ion you have to name it based upon the anion that is part of the acid so the name of an acid is going to depend completely upon that anion right so what we're going to do is we're going to conjugate that anion name and call it an acid okay and there's a few different cases we can have simple binary acids this is where the anion is something like chloride iodide or even cyanide now remember cyanide is considered a monotonic anion so that's a little bit funny all right so if we have the simple anion a simple monatomic anion and we turn it into an acid by adding h plus to the front of it the rule is to call these species hydro root of the anion and we change the ide to ick and then we call it an acid right so an ide ending essentially becomes an ic acid if that makes sense let's go through these examples chloride turned into an acid is called hydrochloric acid you need to always call these an acid hi would be hydro iodic acid and finally here we have cyanide which is going to turn into hydrocyanic acid so for these simple binary acids remember the ide turns into an ick acid this is going to be a kind of conjugation we're going to see in more complex acids so here's more examples here's hydrosulfuric acid one more example it's very easy to confuse h2s which is hydro sulfuric acid with sulfuric acid itself which we'll mention shortly so if we have a polyatomic anion remember we have two main endings for polyatomic anions we have an eight ending and we have an ick i'm sorry we have an eight ending and we have an eight ending right if you remember sulfate and sulfite so an eight ending on the anion turns into an ick acid no hydro no hydro and an eight ending change in changes into an us ous acid so if we look at these examples over on the slide hno3 contains nitrate so nitrate becomes nitric acid eight becomes acid sulfate becomes sulfuric acid right and there's the example we compare with h2 so4 sulfuric acid now another thing that's important is that an acid technically is neutral so we have to add enough h plus ions to the front of this anion to make a neutral compound okay and finally here we have the acetate ion this is one of the polyatomic ions we need to memorize acetate c2h3o2 that becomes acetic acid very common household acid so here's the the ite endings changing into acids here we have nitrous acid which comes from nitrite nitrite becoming an acid is nitrous acid sulfite becoming an acid is sulfurous acid similar to h2so4 and here we have chlorite becoming chlorous acid it's worth it to go through these halo oxoanions right so we could have h o h b r o two h b r o three and h b r o four do you remember what these anions are called so we don't get mixed up let's start from the middle remember we start from the middle and start with the one with more oxygens so here we have bro3 bromate so this becomes bromine acid right above it we have bro2 which remember is bromide so this is going to become bro mus acid that corresponds to chloros acid over here on the slide we go one fewer remember and that gives us hypo hypobromic acid finally if we go back down to the bottom hbro4 would be per bromic acid now we have to talk about one more species that's pretty common to see and that's an acid salt an acid salt is kind of an incomplete acid right so let me give you an example if we have h2so4 we can lose one proton from h2so4 and become hso4 minus this is technically not a neutral acid but it is an acidic compound and there's two ways to name this we can name this hydrogen sulfate let me circle this so we make sure we know we're talking about hso4 minus or this is also called bisulfate which is considered a common name in other words it's non-systematic so you can see if we have this special case where we're creating a kind of new polyatomic anion by the addition of hydrogen it's not yet neutral making it an acid then we just call out the hydrogen and name the anion here's another example hpo2 for two minus this would be called hydrogen phosphate now especially in the case of phosphate you want to be careful because you could also have h2 po4 minus we can add one more hydrogen and we're still not neutral yet what do you think this is called well this is one of those cases where we have to give it a numeric prefix to totally avoid confusion any other way to name this is going to be confusing so it's one of the rare cases we see a numeric prefix in something that is an ionic compound or close to an ionic compound this is going to be dihydrogen phosphate now these are not quite acid salts yet but an acid salt would be something that is a kind of in-between acid anion as we just mentioned here but we make it neutral with the addition of something like potassium or sodium potassium or sodium so let's take our first example hydrogen sulfate what if we make this a neutral compound with sodium well if you think about this this is a salt in other words an ionic compound so what we want to do is we want to name this like we would name any other ionic compound cation anion what is the cation the cation is sodium what is the anion the anion is hydrogen sulfate so this is sodium hydrogen sulfate we could also name it sodium bisulfate so very often if you see something with an extra sodium or potassium out front just try to name it like a salt and even though the anion part might be a little bit more complicated than you're used to seeing you can usually puzzle it out and figure out what it name is so let's do a little self test let's see if we can figure out which of these compounds is named incorrectly kno3 well k is potassium and no3 is nitrate not nitrite so that one's okay let's look at this compound well here remember titanium is a transition metal in order to figure out the charge in the transition metal we have to look at the anion part here we have two oxygens we assume each oxygen is an oxide so two oxides equals a minus four that means the titanium has to be titanium four to make this compound neutral so b is named incorrectly in c we have sno oh4 hydroxide is -1 there's four of them that makes a total of minus four charge that means the tin sn has to be plus four so that one's okay here we have a non-ionic compound a covalent binary compound we have five bromines and one phosphorus phosphorus penta bromide that one's okay and here at the end we have cro4 two minus which is chromate so this is calcium chromate that's okay okay so let's do a quick final quiz on a couple of these i'll give you a chance maybe to think about these in your head or maybe write them on your paper the first one is if3 no metals in this compound so this is a covalent compound we need to specify both element and number iodine trifluoride this next one is a little bit tough it's an acid correct because it has the h out front so we know this is an acid what is the anion c2o4 what is that anion that i anion is oxalate so an oxalate making it an acid we change the eight to an ick acid this is oxalic acid here we just did this example a couple minutes ago we have a salt a sodium salt the anion is bisulfate or hydrogen sulfate so this is sodium hydrogen sulfate and finally we have a metal containing compound but it's a transition metal so we have to be careful we have two oxides for a total of minus 4 on the oxides that means the v the vanadium has to be vanadium 4 to make it neutral here's a few more we can go through and get the formula from the name for some people getting the formula from the name is easier and for others going the other way around is easier it's always a little bit easier for me to get the formula from the name nickel 2 phosphate that means we have i guess i'll write it over here we have nickel two plus the phosphate ion which is three minus i know i have the answer here but this is a case where we can kind of crisscross the subscripts and i three po4 two there we have it eidoic acid idoic acid so the the first um feeling you have is it's probably hi right because that's iodine but remember this simple binary acids get that hydro out front so this hi is hydroidoic acid so what's eidoic acid we have to kind of work backwards in ik acid comes from an ate so that's i this comes from iodate iodate is io3 minus so idoic acid is going to be hio3 this is one of the tougher ones diphosphorus pentoxide well that means two phosphorus and five oxygens these are usually pretty straightforward to get and potassium superoxide well here we want to remember what superoxide is superoxide is o2 with a single minus so we have to make that neutral with potassium so it's ko2 okay so that's it for chapter two first chapter of the semester i hope we have a good semester together and um hopefully this is just a supplement for you and we're actually in person but if this is the main thing then we'll see you in class to do some in-class activities