General Chemistry Lecture Notes

all right welcome to chem 1a so this is the first class in the general chemistry series here so we&#39;re going to go over we&#39;re going to start with just some general introduction to the course and some fundamentals and these are the things that you&#39;re sort of already expected to know when you walk into the class we have a bunch of homework on that set up for you so that you can go through and you can learn everything you need to know about it in the meantime I&#39;m going to cover some of the important aspects of it today and maybe next class so over the course of the class we&#39;re going to cover the first four chapters in your book in the Atkins book so we&#39;ll start off just a cursory overview of the fundamentals things that you would have learned in high school or chem 1p and we&#39;ll go over that in just skimming the surface of it and let you take care of most of that at home then we&#39;ll it start into chapter 1 and this talks about quantum mechanics and atoms at the very very basic level and we&#39;ll do lots of lots of material on that and and spend pretty much the first 4 weeks or so on that your first midterm will cover just chapter 1 from there we&#39;ll move on and we&#39;ll start building molecules out of these and we&#39;ll go into a little bit more complicated structures will learn about geometry and we&#39;ll learn about all of the ways that these look and interact and how they form bonds in more detail rather than just saying that they bond together how do from that point we&#39;ll also learn how they interact with each other how one molecule can interact with another molecule and the way in which these these can change based on on the different properties of the molecules and that&#39;ll be what your second midterm is on at that point we move on to chapter 4 which we start learning about these in both properties so we&#39;ll start learning about gases and how gases interact with each other and and we&#39;ll it will do that for the final so for the entire fundamentals section where this is the things that you already sort of know and I say that theoretically because it&#39;s probably back there somewhere from 3 years ago when you took high school chemistry in 10th grade so go back and review it all that&#39;s you know a through n in your book for a JK and L we&#39;re not going to really talk about that at all I gave you a little bit of homework on it that&#39;s gonna be really important for one seat and if you have me for one seat I&#39;ll test you on that when we get there for this class I&#39;m not going to test you on that at all and I&#39;m not going to talk about it at all but everything up and through J is your responsibility and is what we&#39;ll sort of go over in class today so with all that in mind let&#39;s start in on this we&#39;re going to start with significant figures this is really important and sometimes gets forgotten about and this is a way that we measure how precise we can be in any of our calculations so for every calculation you do in this class you&#39;re going to have to worry about significant figures so there&#39;s a few different rules for this the first one is sort of nice anytime you have a nonzero number this is going to be a significant figure so in every calculation you&#39;re do you&#39;re going to count up all your significant figures you&#39;re going to decide how accurate you can be so for instance with this one it says 54 we have two significant figures and what that means is that we can be accurate to this 54 place or to this ones place right here now when we get to zero that&#39;s when things start to get a little bit more complicated so first we&#39;re just going to talk about what is and isn&#39;t a significant figure then we&#39;ll go on how to calculate um with them so if you have a zero that&#39;s between two other digits so for instance the zero where you have a zero in between a five and a four that&#39;s going to also be significant so in this case where we have five hundred and four the five and the four are significant as well as the zero that&#39;s between them now if we have zeroes that are left of the first non-zero digit so I asked some examples here we have zero point zero zero five zero four something that you&#39;d see pretty regularly you know a decimal point and then this one which is a little bit more strange and not something that you would ever see really written out but just in case I&#39;ve included it in this case we don&#39;t count either of these zeros these zeros I think we can kind of see why they&#39;re not significant these they&#39;re just placeholders we can&#39;t write point five zero four and how&#39;d it be the same number as point zero zero five zero four there are simply placeholders so they&#39;re not significant now if you have numbers that are greater than 1 and you have zeros that are to the right of the decimal place those are definitely significant if you can if you think about it you can think about this without actually memorizing the rule could we just write two well sure of course we could just write two that wouldn&#39;t change the number at all so there&#39;s no reason to include this point zero zero zero zero unless you&#39;re doing it for the sake unless you are doing it for the sake of showing how precise you can be that you cannot only just page two this one this one place but you can go all the way out to here and so those are all going to be significant now when you compare that to up here remember I said you can&#39;t just write point five zero four that changes the number so here these are placeholders here these show precision now this next part says trailing zeros aren&#39;t significant unless the decimal point or scientific notation is used so for instance here I had just have four thousand two hundred there is no decimal point after those two zeros aren&#39;t significant and that&#39;s because you can&#39;t just write 42 there and have it be the same number those zeros are just placeholders anytime we have a zero that&#39;s a placeholder it&#39;s not going to be significant anytime you have a zero that isn&#39;t a placeholder like for instance here those are now what if we wanted all of these digits to be significant we can force them to all be significant by putting a period at the end so if we just put a period at the end or a decimal point at the end then that forest is that tells whoever&#39;s looking at your work that you really can measure out to the ones place it just happens to be that in this case both the 10 and the ones place is 0 now what if we wanted just for two and we wanted that first zero to be significant there&#39;s a way to do that to scientific notation is the way to say exactly what want to be significant and what you don&#39;t so in this case we can write out 4.20 and that says hey everything that we have written in the scientific notation that&#39;s significant so if you have it and you have written out in scientific notation whatever is there is going to be significant so if you ever get to an exam it rounds up to something like four four thousand two hundred and you say but I need three significant figures how can I write that down how can I get that point on the test well it&#39;s going to be by going through and putting it into scientific notation so that I know that you know that is three significant figures now the next part of this is how do you do calculations with these because of just being able to count how many scenes he figures you have is great and for something like taking a measurement that would that would be fine but you also you&#39;re going to be doing actual calculations you&#39;re going to be plugging things into equations maybe something that has three significant figures and something that has four significant figures and you need to know how many come out at the end so there&#39;s two different sets of rules there&#39;s rules for if you&#39;re doing addition and subtraction and they&#39;re all sort of you&#39;re doing multiplication and division so for addition and subtraction you use the lowest number of places or decimal points so you&#39;re not actually going to be counting significant figures as we&#39;ve just talked about on the previous slide for addition and subtraction so for example let&#39;s say we&#39;re adding on point two four so something with a once place in a tenth place and something like point three four five where you have a one up to the thousandths place you round this to the lowest number of decimal places so in this case two decimal points or two decimal places and so you would round it to point five nine you&#39;re not counting significant figures here you&#39;re counting decimal places so what if you don&#39;t have a decimal what if you&#39;re just sitting in the higher numbers well in that case you just round to the number of places so here we&#39;re all the way out to the ones but here we&#39;re only at the hundreds so when you round this you round to the nearest hundred and so you end up with forty five hundred so that&#39;s for addition and subtraction you&#39;re not counting sig figs just play whether that be decimal places or places before or to the left of the decimal point with multiplication and division that&#39;s where you&#39;re going to bring in all that significant figures that we did in the previous slide so for multiplication and division you go to the lowest number of sig figs so if we look at 23 we can see that there are two significant figures if we look at 436 we can see that there are three significant figures so when we want to round this we want to round to what there are two significant figures now if you go ahead and plug this into your calculator for me real quick you&#39;ll see that when it rounds we end up with a 1 and a 0 and we can&#39;t and you might say well how do I round that can I just put you know 10,000 well you can&#39;t just put 10,000 because that would then have just one decimal or just one place one significant figure and you need to have two so you would say okay well now I have to convert it into scientific notation so that I can put the point 0 there so let&#39;s do another one with division so here we have four hundred and fifty three divided by three point two so sure we have a decimal place here but that doesn&#39;t make any difference we don&#39;t have to pay any attention to the decimals we just go through and count how many sig figs do we have so here we have three and here we have two so when we get all done with that that means that we&#39;re going to have two significant figures and so we&#39;re left with 140 now some rules for how to actually work with these so these are the rules for coming up with an answer that you&#39;re going to turn in and that&#39;s fine if you only have one or one step you can just say okay well I&#39;ve added these two numbers I&#39;ve multiplied these two numbers whichever and go ahead and put it down on the paper but if you have five or six different steps you&#39;re taking an answer for one equation and filling in another equation now you have to kind of keep track of this it is not a good idea to round at every single step that introduces a little bit of an error every single time and there&#39;s a good chance that you&#39;ll start getting answers wrong especially on you know sort of on line systematic homework so what you want to do is you want to hold out a few decimal points to be honest when I I just keep them my calculator and second answer the whole way through if you want to write about that&#39;s fine to just write out a couple points past the significant figure the last thing event figure then you might say okay well how am I supposed to keep track of what&#39;s going on then how can i if I take the answer from one equation and I add all these extra sig figs how do I know how many sig figs I have there just put a little underline under the lasting fan one and then you&#39;ll see this when I start doing some work but every time I get done with an answer that I need to use someplace else I put a little underline under the last significant figure so I can keep track of it so that&#39;s some kind of hints for actually going about doing this and you know real problems okay so that&#39;s one of the most basic things that you&#39;re going to have to know to do every single calculation problem in this class now the next set of things that you&#39;re really need to have a good background on is something called dimensional analysis or conversion factors and these two are sort of very much interrelated to each other the idea with a conversion factor is you have something that says this much is equal to this much of something else so 100 centimeters equals one meter that&#39;s a conversion factor now the way we use this is through something called dimensional analysis it&#39;s one of the main ways anyways where you can go through and you can convert one item into something else using conversion factors the easiest way to do this is to actually go through and do a few example problems and so that&#39;s what we&#39;re going to do all right so we have your worksheet that you&#39;ve printed off from the internet and we started out by saying the average speed of helium at 25 degrees is twelve hundred and fifty-five meters per second and I say convert that to miles per hour so the way that you want to always think about conversion factors is writing down what we have and write it on what we&#39;re trying to get to and seeing what you need to do in between so we&#39;ll start by writing down what we have so we know we have this and we know at the end of the day we need to have miles per hour so now how do we get between them using only conversions that we know or can easily look up I ask you to memorize all of the metric conversions I don&#39;t care about the other conversions I would give them to you the metric ones you have to know so if we have meters on top we need to do something to get rid of meters having something in the numerator is saying that you&#39;re multiplying it so the opposite of multiplication is division so we put that on the bottom and we know that we can get from meters to miles through using some sort of conversion factor that we either look up or have memorized more likely look up and so we&#39;ll put miles up here now we go when we find that conversion factor and we say well for every one mile there&#39;s 1609 point three meters when you look up these sorts of conversion factors that aren&#39;t nice round numbers it&#39;s not something like in the metric system where you have one in ten and a hundred and a thousand you want to keep one place more than or one significant figure more than what your actual number that you&#39;re starting with is so if we think about how this cancels we now would have miles per second if we keep track of all or all of our units we don&#39;t want miles per second we want miles per hour so now we have seconds on the bottom and we want to get rid of that so that means we have to put seconds on the tops to cross that out and we want hours on the bottom so we&#39;ll do this and then we fill in this conversion factor of course this would be one that you&#39;d be expected to know and if you didn&#39;t remember that off the top of your head you know how many seconds are in a minute so you could convert to minutes and you know how many minutes is in an hour so you can convert to hours from this point now we can look and we can see that our meters cancel and we can see that our seconds cancel and we can see that we have miles per hour so our units are all set which means our answer is going to be fine and we can do 2807 so you can see that that&#39;s much easier to figure out how to do than to try to memorize well am i multiplying by this conversion factor am i dividing by this conversion factor what am i doing so this way you can just trace your units around okay we have one more of these to do see how many minutes does it take light from the Sun to reach Earth given that the distance from the Sun is 93 million miles and the speed of light is 3 times 10 in the m/s or 3 times 8 meters per second okay so to do this one now this one I&#39;m kind of asking you a real question but it really turns out to just be a bunch of conversion factors put together if we know that we have a certain amount of miles and it&#39;s 93 million which means it&#39;s 93 times 10 to the 6 and now the end of this we want to get to time so we need to trace through all the conversion factors that we can find in order to get this well we can start by saying we have we have miles here and we know our speed is in meters per second so we have a distance here and we have a time that&#39;s going to be a good way that we can go through and try to get to time but it&#39;s not going to work with miles so let&#39;s change miles into meters and we&#39;re going to do that the same way that we did here now notice on the second problem though if you look back to your first one the the ordering is flip-flopped and that&#39;s because we&#39;re converting from miles to meters instead of 4 meters to miles so we can write in those numbers and you can also hold off and write in all the numbers at the very end - so now we know that we have meters on top and our miles cancel out and we can look at what else we can do we want to get from a distance to a time so we need something that has both distance and time in it now from there we need to decide well we&#39;re going to multiply by this number or are we going to divide so again we trace through our units we have meters on top and we don&#39;t want meters so we divide by it so that leaves us with seconds on top which is what we want because that&#39;ll end up with our time in it so now we fill in our numbers the number here goes with the meters because it&#39;s on top three so three point zero zero times 10 to the 8th and we put one second here now at this point we want to look at what I had asked you for so we could do this in seconds if we wanted but I had actually asked for minutes and so at this point we can see well we have seconds so we need to convert that into minutes and we know that we have 60 seconds in one minute so that gets rid of this unit leaving us with minutes which is what we wanted and we can solve for that now it&#39;s time to take a look at our significant figures here for both of these so now we have them both up now notice on this one I put I left it as four significant figures now I need to go back and say okay for all of these calculations did we do this right we started with four significant figures here we divided by five here and we did that on purpose all right we looked up that number and we said okay well we have four significant figures here I need to keep one extra now what about this one that 3,600 does that mean that we should round 228 or 2800 well no whenever you have a definition you don&#39;t run into that so there is exactly 60 seconds in one minute there is exactly 60 minutes in one hour there is exactly 3600 seconds in one hour it&#39;s defined that way and so you can think of it as being infinite significant figures however many you need there to be so that means that this is going to be left as 4 because we started with 1 now when we come down here we started with 2 here we again look this up I put it as 5 basically just because I had that number handy but you could have got rounded it to 3 if you had wanted we have this number which has 3 significant figures and then we have this one which looks like 1 but remember it&#39;s a definition and so because of the definition it&#39;s actually infinite and so the only thing that matters for our significant figures is the 93 so we have two significant figures here and so we need to have two significant figures here okay so that sort of walks us through some of the calculations that we&#39;re going to be doing in a very general format where you don&#39;t need to have a lot of chemistry background yeah you&#39;re you can always use dimensional analysis and looking at the units and crossing off the units as a double check whenever you go to do anything so every problem that you do you should write out all of the units all of the time and then each time go through and look at where they are and look at how they cancel and make sure that at the end you have a unit that makes sense if you&#39;re measuring distance and you come out with a unit of time you did something wrong if you&#39;re measuring you know velocity and at the end you need to have a velocity and you come out with something like meters and note second per second you did something wrong so this is a great way to go through and make sure that you did everything okay we&#39;ll get to we&#39;ll get to times later on in the quarter where we have a constant that has tons of different types of ways of writing it in and all of the differences are with units how do you know which one to use you can memorize it and you can say well when I use this equation I&#39;m going to use this version when I use this equation I&#39;m going to use this version or you can just look at the units and say okay I know I have liters and atmospheres so I&#39;m going to use this version of our or I know that I have joules so I&#39;m going to use this version of our things of that sort okay so now we&#39;re going to get into the structure of an atom and we&#39;re going to do this at a really basic level right now and then chapter one we&#39;ll get into it in much much greater detail and in some ways I&#39;ll tell you that we lied a little bit here so this is the Bohr model of an atom and I like to sometimes call this the high school model this is sort of the first model that we teach you it has some very good uses some of which we&#39;re going to take advantage of here starting this classroom next but it also isn&#39;t a hundred percent accurate but it&#39;s a good starting point so we&#39;ll kind of start from there here you can think of it as being a nucleus in the middle that has two different parts of it it has protons and it has neutrons the protons have a positive charge the neutrons have no charge at all and then around this nuclei going in right now we&#39;ll think of it as rings and later on we&#39;ll expand that a bit that you have electrons and those electrons are negatively charged so there&#39;s some things you want to be able to look at a periodic table and calculate pretty quickly without having to put a huge amount of thought into so if you don&#39;t know how to do this is fine but you want to go get some practice at it so if you have the number of protons you have and you subtract the amount of electrons your protons do I have a plus 1 charge your electrons have a minus 1 charge so that&#39;s going to give you the charge of the ion now in any sort of neutral compound this is the third atom that&#39;s 0 because you&#39;re going to have the same number of protons electrons but you can also start adding and subtracting protons and electrons as time goes on and making ions out of them and we&#39;ll talk about that in much more detail too so keep this in mind that your charge is always going to be equal to your protons minus your electrons now if you look at your periodic table there&#39;s a bunch of different numbers that you can you can deal with one of them is your atomic number that&#39;s your number of protons and then there&#39;s also an atomic mass an atomic mass is your number of protons plus your number of neutrons and so you can take those and you can add them up and that gives you your atomic mass because you&#39;ll always have a periodic table you&#39;ll always know your number of protons you&#39;ll always know your atomic mass for any sort of exam or anything like that and what you&#39;ll see is a lot of times will King calc back calculate and figure out how many neutrons we have we can take your mass and subtract your protons and get your neutrons and we&#39;ll do that a lot in one scene when we start getting into a nuclear chem now you really have to remember these charges which ones are positive and which ones are negative and in order to help remember that we have a little joke lots of great and simultaneously horrible chemistry jokes out there this is one of them so you have two neutrons and they walk into a bar in the order a couple of drinks as the one about is about to leave the waiter says how much does it cost and Neutron set or in the let me start over okay a neutron walks into a bar orders a couple of drinks as she&#39;s about to leave she asked the waiter how much and the way to reply is for you no charge that&#39;s the joke to sort of remember what a neutron is we have another one here and this one is one of the most famous one that gets repeated over and over and over again and you have these two different atoms and they&#39;re talking to each other and the one says I&#39;m hit im hit I&#39;ve lost an electron and the other one says are you sure and the first one says I&#39;m positive they lost an electron and so they&#39;re positive right so two two nice horrible jokes for you to remember these by lots more of these as a quarter goes on okay so now comes some sort of time for just general definitions so first of all we have something called an isotope what is an isotope so anytime that you have the same number of protons but you have a different molecular mass that&#39;s an isotope and the reason why you get this is because you have different numbers of neutrons and so your neutrons within one particular atom can change and without really changing too much of the properties we&#39;ll see again in one see that some of the properties definitely change the mass definitely changes because you&#39;re adding in a neutron which has it has a mass of about one but most of its properties are very similar now why are the molecular masses on the periodic table of decimal points so you should probably always have a periodic table handy in this class just kind of sitting out starting next class you probably want to do that there&#39;s you know they&#39;re around so whenever you look at this you&#39;ll see that your molecular masses are decimal points and why is that well the reason for that is that they&#39;re actually going to be an average they&#39;re going to be an average of both or all of the isotopes of that compound or that atom so something like silver has two isotopes that make it up sometimes you&#39;ll get silver 1:07 if you were to weigh the Mastiff that one Adam you come out with a unit or 107 sometimes it&#39;s 109 so on the periodic table what they do is they do something called a weighted average and you know weighted averages are a good thing to know how to do if you don&#39;t know how to do that reviewed in your math class it&#39;s also how your grades are figured out you know so when you go to figure out your grades and I say figure out a weighted average that that&#39;s what I&#39;m talking about and that&#39;s how it&#39;s that&#39;s how it&#39;s determined here so in this case we would have 107 silver making up 51% 109 silver making up the rest well it will do this out on the document camera in just a minute you&#39;ll notice some of these are even more complicated some of these will end up with two or three different isotopes now the reason we do a weighted average as opposed to just averaging it you may say why can&#39;t I just take this and say well 107 plus 109 divided by 2 well we want to know what the mass of this is we go out into the world and we take some silver out of the you know some silver out of the ground clean it up get rid of all the ore and purify it how much is that silver what&#39;s the molecular mass of that silver and now all of the silver is split 50/50 107 and 109 and this is where the idea of weighted averages come in so we&#39;ll do this one out on the document camera so we can see it all worked out okay so we have 51 point eight three nine percent of silver is 107 so we need to figure out how much of how much there is at each so we know this because the problem says so now we also need to know what percent is 109 well it&#39;s the rest of it so we just take 100 subtract that so this is 100 minus the silver 107 percent which gives us the forty eight point one six one now we do what we call a weighted average so I&#39;m going to do it out in two steps you can do it out in one it&#39;s you find either way so if we know that we have 107 grams of this we can just say that we have 107 grams per mole and 109 of this what we&#39;ll do is we&#39;ll go through and we&#39;ll multiply that by the percent and the same thing here so we&#39;ve taken 107 multiplied it by the percent that makes it up in in nature this multiplied by the percent that makes it up in nature and we get those two numbers and then we add them all and we get that now with everything in chemistry you want to be thinking does this make any sense now in this case we have a weighted average between two things it&#39;s 107 and 109 and it&#39;s about 5050 right ones 51 ones 48 it&#39;s about 5050 so we would expect the answer to be close to what the normal average would be or what the real average is which is 108 so since we have this in this being added together almost equal proportions we want it to be close to 108 with a little bit less because the 107 the lower number has a little bit higher percentage and that&#39;s exactly what we see we see that as close to 108 just a little bit less than 108 so that makes sense based on the averages and what we know about how averages work and so that&#39;s it now this was a case where we only had two Isis hopes that we were averaging you could do this for more something like carbon has one main one and then two smaller ones you could do that for each and you would just do this three times and then add it all up okay so now that we know all these things about atoms we know they&#39;re protons we know there are electrons we know they&#39;re neutrons they&#39;re masses we need a nice way of looking at all this data and figuring things out very quickly and this is where the periodic table comes in we have all the elements arranged in order of increasing atomic number so atomic number remember that&#39;s the number of protons that we have now they&#39;re arranged in these repeating patterns and we&#39;ll get into more detail about exactly how that is but for right now what you can know is that they have the same number of what we call valence electrons outside shells if you think about the Bohr model you can kind of think about they&#39;re those rings right and whether they&#39;re filled or well how many they have in those outside rings and so what happens there is that gives certain columns or groups similar properties so everything that&#39;s going to be in Group one is going to have a relatively similar property to each other now of course there&#39;s going to be differences because the atomic mass here is much much bigger than here the number of protons the number electrons are much bigger and there&#39;s some trends that we&#39;ll be able to pull out of the periodic table later on but for the most part this group would have the same sort of trends as E or the same sort of properties as it struck each other this group same sort of property does each other all the way across the periodic table so if you go down a column you have very similar properties now this happens to be my sort of favorite periodic table that I I carry around and you don&#39;t have all my books I actually replace a lot of my book periodic tables with this one you know find your favorite periodic table from the internet we&#39;re in it out and keep it with you all the time in class and when you&#39;re doing chemistry I don&#39;t really expect you going to the bars with them and such things but keeps them around you whenever you&#39;re doing your homework keep them out in class with you because I&#39;ll refer to them a lot okay now something that we&#39;re going to get into a little bit with naming and this is probably all of the freshman chemistry students least favorite part about this class because there&#39;s a lot of memorization in general I say with chemistry you shouldn&#39;t be memorizing hardly anything if you&#39;re memorizing things you aren&#39;t in general are not learning them um and in chemistry that gets dangerous if you memorize how to do a problem you&#39;re probably going to have problems on an exam because I&#39;m going to give you one that&#39;s a little bit different and if you don&#39;t really know what you&#39;re doing you&#39;re not going to be able to solve it because it&#39;s not going to be the exact same as your homework problems this is sort of the exception to that you have to do a lot in a lot of memorization for the ionic naming it&#39;s a pain just do it you&#39;re going to need it for one B you&#39;re going to need it for one C and you just need it to be around chemistry in general which includes the biology that you&#39;re going to be in you you want to have a good idea of what&#39;s happening you want to be able to look at a compound and name it quickly without having to think about it too much I can test you on this in the first midterm just by saying here&#39;s a name you know give me the formula here&#39;s the formula give me the name I can do it on the second midterm by saying draw me this compound and if you don&#39;t know how to name it you don&#39;t know how to pull the formula out of the name I gave you you won&#39;t be able to do it so make sure you just go through and do all of this so before we can get into naming too much we have to figure out how do we know what type of naming we&#39;re going to do so up here I have we have ionic molecular acids inorganic now we&#39;re going to get very much into ionic molecular in acids those are the ones that your testable on in this course for organic you have a homework assignment on this we&#39;ll talk about it a little bit don&#39;t worry about it too much in general that&#39;s all going to be covered in really great detail next year but you should have a general idea of how it works because I&#39;m going to talk about it I&#39;m gonna say things like methane and ethane and you know ethanol and propanol and you should have some idea of what I&#39;m talking about I&#39;ll also always have the structure up there but you don&#39;t want something like that that to throw you off and so just have a general idea of how it works be able to answer questions on it if you have the book in front of you we&#39;re just not going to get too into it this or this class that&#39;ll be more for next year these three are the ones we&#39;re going to focus on now all of these are going to be named very differently if you have an ionic compound is named completely differently than a molecular compound you&#39;ll learn to like the molecular ones for the naming purposes here and assets are going to be sort of based off the ionic nomenclature but that&#39;s still very different and so before we can actually get into the rules for naming we have to get into how we know which one is which type of compound so to do this we have to talk a little bit about bonding and how things bond so whenever whenever something is trying to bond with another atom it&#39;s trying to do what we call complete an octet now we&#39;ll see some atoms don&#39;t actually do that exactly but they&#39;re trying to they&#39;re trying to get a full octet which means that they would have eight atoms or eight electrons in their outside shell so if you have one atom that has six in its outside shell and another one that has six in this outside shell it can go and it can form a bond now in this case it&#39;s going to want to share those electrons because you have six here and six here so this one can&#39;t just give two of it away or it&#39;s going to have some problems this one can&#39;t just give two of them away or it&#39;s going to have some problems there are times when you can do that when you can just trade electrons and there&#39;s times when you have to share electrons and that&#39;s your difference between your two different types of compounds there are two different types of bonds so for ionic compounds that have ionic bonds they&#39;re going to trade electrons one one atom is going to give away its electrons to the other one so something like sodium chloride so if you take and you look at your periodic table a minute and you look at sodium three here and you look at chloride right here you can see that sodium has one electron it&#39;s outside shell and the periodic table is really nice for looking at this quickly because you can look here and say okay this has one valence electron this has two valence electrons three four five six seven and eight all the way across so we can use this to look and see how many valence electrons we have very quickly so sodium has one and chlorine has seven so they can just trade electrons the sodium will say well I don&#39;t really want one electron sitting there by itself you take it and gives it to the chlorine the chlorine says great this gives me eight so now they both have eight in covalent bonding they&#39;re sharing the electrons so this would be something like carbon and oxygen or two oxygens or two fluorines where they don&#39;t they can&#39;t just give them away they&#39;d still be too short of electrons and so instead they&#39;ll share them carbonyl gives let oxygen take some of them oxygen rule that you know did you solve them and then you count those electrons for both we won&#39;t get too into metallic bonding but it is important to talk about and have sort of in the background now and metallic bonding you have these big networks in these big networks of electrons that can move back and forth between all of them here and here you sort of have the electrons that are relatively associated with one or two groups here they&#39;re completely delocalized which means that you can kind of move them from one side to the other if you do the right sort of thing to it and we call this you know a wire right we can take a wire and we can stretch it out that&#39;s all metallic bonds we can put electricity through it and the fact that you have these delocalized electrons that are going across this entire group is what would what allows that to happen and those are for metallic bonds but these are the two we&#39;ll be focusing on for the sake of naming okay and one last thing we need to talk about here is something called empirical versus molecular formula now this comes up in covalent bonding not anionic so keep that in mind you may even want to write that down this is just for covalent issues with ionic compounds we&#39;re always going to listen as the lowest whole number ratio so we would never say ng 2 O 2 or na 2 CL 2 we always want to reduce them down to the lowest amount with covalent bonding that&#39;s not necessarily how things work something like hydrazine if you look at this we have n 2 H 4 and you could say well can I reduce that down to NH 2 well you can&#39;t because it changes the whole compound n 2 H 4 is not the same thing as NH 2 so we have to have some nomenclature for this that we&#39;re going to refer to from time to time so we have an empirical formula which is our lowest whole number ratio doesn&#39;t actually tell us a lot about the molecule itself but it does tell us how many of each atom are in the substance and then what the molecular formula is going to tell us is it&#39;s going to go through and say well this is how this is what the molecule actually has in it one molecule hydrazine actually has two nitrogen&#39;s and four hydrogen&#39;s or ethane two carbons and six hydrogen&#39;s now we&#39;ll do some examples using this where you can see that we can find the empirical formula fairly easily experimentally and we can find the molecular mass fairly easily experimentally which is why one of the reasons that this is so important to have these differences here so that goes into a little bit more of covalent bonding definitions now I&#39;ll spend some time on ionic bonds and then we&#39;ll learn how to actually name them so this is the day filled with bad jokes so we have another one so the way that ionic bonding works is by the fact that these atoms will trade electrons and when you trade electrons electrons have a negative charge and so there&#39;s going to be a charge development if you trade electrons like that so we have you have this teacher up here and you have these little atoms here all these positive ions since perhaps one of you gentlemen wouldn&#39;t mind telling me just what it is outside this window that you find so attractive so remember positives and negatives are always going to attract each other right so if you take an electron you take it away from one atom you make it a positive charge you&#39;re taking a negative charge away you&#39;re making it a positive charge you&#39;re giving it to another atom which means that that atom is going to be a negative so you have a positive atom now and a negative atom those two are going to attract just like a magnet would and that&#39;s how you form your ionic bonds so how do we actually write this out quickly well we do this we can do this this way where we have ionic bonding here we take something like potassium and if you look at your periodic table you&#39;ll see that potassium has one electron it&#39;s in that first group and so it has one valence electron if you look at iodine so you&#39;re you know you&#39;re looking at your periodic table you&#39;re finding it on the periodic table you see iodine is in the seventh group so it means it has seven electrons so how can we get this so they both have a full octet well we&#39;ll take the electron away from potassium we&#39;ll give it to iodine when we do that potassium develops a plus charge you&#39;ve given away one of its electrons iodine has developed a negative charge because you&#39;ve given it to iodine and so you get this structure where you form the positive and the minus they attract and they form potassium iodide the exact same thing can happen where now instead you have to give one electron away to two different atoms so if you&#39;re trying to combine something like magnesium along with something like fluorine now you have an issue where you have two electrons in magnesium outside shell and fluorine only can take one well you just take double the amount of fluorines so now magnesium says okay I&#39;m going to give you one electron I&#39;m going to give you an electron both of the fluorines develop a negative one charge the magnesium gets a +2 charge and they all tracked each other and they form this structure which means that then you would have ngf 2 1 mg in two fluorines now that&#39;s how you want to know what what&#39;s going on and how these are treating whether they just trade one and become k+ and i - in this case or sodium chloride would be the same same form or whether you have MGF - it&#39;s all about the charges and making sure that the charge is balanced now there&#39;s a quicker ways of doing this though than trying to write this out each time and think about exactly where the electrons are moving around each time so here&#39;s a helpful trick to remember it so you can kind of take the charges and you crisscross them now you might be saying how do I know what the charges are basically through memorization and we&#39;ll get into that in just a moment so if you write down the charges here and the charges here and you know that your ions have these charges you can crisscross them down you can say well I&#39;m going to Chris I&#39;m going to move this down to the oxygen I&#39;m going to move this down to the aluminum now what that ends up doing is it gives you a compound where your charge is balanced you can say okay aluminum has a +3 charge and I&#39;m going to multiply it by 2 now that it means I have plus 6 oxygen has a minus 2 charge and that but there&#39;s three of them so minus two times three that&#39;s minus six so now you add up here plus charges and your minus charges and they need to equal zero and in this case you see that they do so this is sort of a helpful trick for getting you to this neutral compound faster you want your ionic compounds to be neutral there is one major caveat to this though that you have to watch out for if you&#39;re going to use this little quick trick and that is that goes back to this idea of empirical formula and molecular formula and how that&#39;s only true in covalent we only deal with that in covalent ionic always need to be the lowest whole number ratio what if you have something that had the same charge and it isn&#39;t one or same magnitude a charge I should say and it isn&#39;t one something like magnesium that has a plus two oxygen that has a minus two you crisscross them down you form mg - OH - that&#39;s an ionic compound you have to have the lowest whole number ratio so this isn&#39;t okay so you need to then reduce down to the lowest whole number ratio so when you do sit down it becomes MgO so at that so whenever you have this sort of situation and you&#39;re you could probably just say okay well these are the same charge so I&#39;m going to say that that&#39;s just NGO but if you didn&#39;t catch that right away you did do the crisscross trick and you saw that this is mg 202 you have to reduce that down now something that we are going to just sort of show you and then move on with is that these form these big crystal lattices and 1b when you first start 1d this is what you&#39;re going to start with and you&#39;re going to learn all about these different shapes in these different forms and you&#39;ll put names to them and all of that and for this class I just want you to know that this exists that when you get these you don&#39;t have one sodium chloride it just stuck together and you have this one little out of the sodium chloride all by itself what you actually have is you have these crystals if you go to you know your pantry and you pull out salt you actually have all these little crystal lattices inside of it and that&#39;s what&#39;s forming so just keep that in the back of your head that this is what these ionic compounds look like okay now how do you know what the ions are so I&#39;ve said that it&#39;s memorization that wasn&#39;t really a hundred percent true so you can look at the periodic table and you can find out what the charges are for the most part there&#39;s there&#39;s some exceptions here but for the most part so if you look at this first row we have one valence electron and you want to find a way to get rid of that so you can go through and you can just take that one electron off giving it a plus one charge or you can take two electrons off from this group giving it a plus two charge this group you would have three valence electrons so you take three off when you start getting into this group now it&#39;s not really going to be able to just gain - or loose there excuse me gain four or lose four as easily so those aren&#39;t going to be big on forming ionic compounds at all when we&#39;re to the right side of the periodic table we look at here how many valence electrons does that have well it has seven what&#39;s going to be easier taking away seven Tron&#39;s or just adding in one well of course adding in one would be easier and so because of that you&#39;re adding an electron you&#39;re adding in a negative charge and so it&#39;s going to be a negative one if you look at this row you have six valence electrons it&#39;s in group six Eve six is it going to be easier to plus six or at into it&#39;s going to be easier to add in two and so you get a negative two charge same thing here easier to pull off five or add in three will add in three so that&#39;s going to be a negative three charge this section in here your transition metals in this little group right here for right now you pretty much just have to memorize them after we start talking about electron configurations in more detail and how to go about dealing with those and seeing where electrons are removed from will actually be able to explain most of them however for right this moment there&#39;s really no way to explain it easily so these groups you just have to sort of memorize and when we get into check the very end of chapter one we&#39;ll learn why all of those are now I do want to help member help you memorize one of this section so this little group right here we&#39;re going to sort of pull out and we&#39;re going to look at in more detail so there&#39;s something called the inert pair effect and I don&#39;t want to go into exactly why this is at the moment um if you&#39;ve had a lot of chemistry and you want me to explain it I can do that later but for now we&#39;re just going to leave it as this is how it works and then at the very end of chapter one we&#39;ll go back and we&#39;ll explain it using electron configurations so for right now you can notice though that these have these groups of 1 3 2 4 3 5 so they&#39;re always off by 2 you can form this top lower ion or you can form this bottom ion and they&#39;re always off by a factor of 2 so use this to help you remember it for right now and we&#39;ll explain why it is later on ok now we&#39;ll finally be able to get into naming these so for here a lot of these listed and there&#39;s copies of all of these sorts of things online this is from a different book but we&#39;ve pulled out all of the ions and put them online for you so the idea to get out of this and the lists online is that there&#39;s also all of these polyatomic ions that we need to talk about those for the most part are going to be memorization but there&#39;s some hints for memorization so everything that I&#39;m about to say we&#39;ve also put into an online study guide that is available um so that you can kind of go through and see what I&#39;m saying when I say eight and i&#39;ts because it&#39;s a little bit hard to hear so these are lists of things that you effectively need to have memorized but there&#39;s tricks to memorizing it that will make life a lot easier so there&#39;s these two these different types of endings and these different types of prefixes so you have eight sites and IDEs as your endings if you have something with an ID ending that is just the compound nut or the atom on its own something like phosphide or sulfide or oxide if you have something with an eight or a knight ending like this that&#39;s going to be your oxygens so something like phosphate or phosphite are going to have oxygens on the end and the ice in the eight refers to how many oxygens or it&#39;s oxidation numbers so what we&#39;ll do here is whenever you have is you should memorize one version of these you memorize all of the eights or you memorize all of the ice you don&#39;t memorize both if you have something with an eighth ending that&#39;s what I happen to memorize when I did this back in high school um or college and I memorized through and I memorized ha State and carbonate in sulfate and then I knew that every time that I changed that to a night ending I just took away in oxygen so if phosphate is po4 three 9s phosphite is po3 three - okay so that&#39;s kind of your hints for doing this now you&#39;ll also see times where you have something like if you look at iron iron has two different oxidation states two different charges so three plus and a two plus and we have a different nomenclature for certain compounds for instance iron where we call it ferrous or ferric and those us in ache endings those refer to the charges if you have an ache ending you would have a three plus charge if you have an us ending you would have a two plus charge the us always refers to the lower charge the it always refers to the higher charge and so keep that in mind when you&#39;re memorizing those weird named ones like iron and lead is another one Stannis and static 410 so there&#39;s these groupings of ones that have two different names one comes from the original Latin root the other one is the name that we know it by and these are pretty easy to pick out of the periodic table because they&#39;re the ones where the element symbol doesn&#39;t really match up with what we know we know that iron does is Fe we know that tin is SN and so those are pretty easy to pick out of the periodic table and I have those highlighted on the study guides as well so make sure you go in you know start working on memorizing those and start working on making sure that you can form those ionic compounds using the ions that you have memorized because again you&#39;ll be tested on this all through general chem and you better just it&#39;s better to just do it now and get all the points starting now rather than waiting till the end to do it next class we&#39;ll get into how to name acids and how to name covalent compounds which are significantly easier than this just because there&#39;s a lot less memorization to it um if this didn&#39;t make a huge amount of sense you know make sure you go and look at the study guide online where it&#39;s all written out with the owe us AAT e and ite endings to help you

all right welcome to chem 1a so this is the first class in the general chemistry series here so we&amp;#39;re going to go over we&amp;#39;re going to start with just some general introduction to the course and some fundamentals and these are the things that you&amp;#39;re sort of already expected to know when you walk into the class we have a bunch of homework on that set up for you so that you can go through and you can learn everything you need to know about it in the meantime I&amp;#39;m going to cover some of the important aspects of it today and maybe next class so over the course of the class we&amp;#39;re going to cover the first four chapters in your book in the Atkins book so we&amp;#39;ll start off just a cursory overview of the fundamentals things that you would have learned in high school or chem 1p and we&amp;#39;ll go over that in just skimming the surface of it and let you take care of most of that at home then we&amp;#39;ll it start into chapter 1 and this talks about quantum mechanics and atoms at the very very basic level and we&amp;#39;ll do lots of lots of material on that and and spend pretty much the first 4 weeks or so on that your first midterm will cover just chapter 1 from there we&amp;#39;ll move on and we&amp;#39;ll start building molecules out of these and we&amp;#39;ll go into a little bit more complicated structures will learn about geometry and we&amp;#39;ll learn about all of the ways that these look and interact and how they form bonds in more detail rather than just saying that they bond together how do from that point we&amp;#39;ll also learn how they interact with each other how one molecule can interact with another molecule and the way in which these these can change based on on the different properties of the molecules and that&amp;#39;ll be what your second midterm is on at that point we move on to chapter 4 which we start learning about these in both properties so we&amp;#39;ll start learning about gases and how gases interact with each other and and we&amp;#39;ll it will do that for the final so for the entire fundamentals section where this is the things that you already sort of know and I say that theoretically because it&amp;#39;s probably back there somewhere from 3 years ago when you took high school chemistry in 10th grade so go back and review it all that&amp;#39;s you know a through n in your book for a JK and L we&amp;#39;re not going to really talk about that at all I gave you a little bit of homework on it that&amp;#39;s gonna be really important for one seat and if you have me for one seat I&amp;#39;ll test you on that when we get there for this class I&amp;#39;m not going to test you on that at all and I&amp;#39;m not going to talk about it at all but everything up and through J is your responsibility and is what we&amp;#39;ll sort of go over in class today so with all that in mind let&amp;#39;s start in on this we&amp;#39;re going to start with significant figures this is really important and sometimes gets forgotten about and this is a way that we measure how precise we can be in any of our calculations so for every calculation you do in this class you&amp;#39;re going to have to worry about significant figures so there&amp;#39;s a few different rules for this the first one is sort of nice anytime you have a nonzero number this is going to be a significant figure so in every calculation you&amp;#39;re do you&amp;#39;re going to count up all your significant figures you&amp;#39;re going to decide how accurate you can be so for instance with this one it says 54 we have two significant figures and what that means is that we can be accurate to this 54 place or to this ones place right here now when we get to zero that&amp;#39;s when things start to get a little bit more complicated so first we&amp;#39;re just going to talk about what is and isn&amp;#39;t a significant figure then we&amp;#39;ll go on how to calculate um with them so if you have a zero that&amp;#39;s between two other digits so for instance the zero where you have a zero in between a five and a four that&amp;#39;s going to also be significant so in this case where we have five hundred and four the five and the four are significant as well as the zero that&amp;#39;s between them now if we have zeroes that are left of the first non-zero digit so I asked some examples here we have zero point zero zero five zero four something that you&amp;#39;d see pretty regularly you know a decimal point and then this one which is a little bit more strange and not something that you would ever see really written out but just in case I&amp;#39;ve included it in this case we don&amp;#39;t count either of these zeros these zeros I think we can kind of see why they&amp;#39;re not significant these they&amp;#39;re just placeholders we can&amp;#39;t write point five zero four and how&amp;#39;d it be the same number as point zero zero five zero four there are simply placeholders so they&amp;#39;re not significant now if you have numbers that are greater than 1 and you have zeros that are to the right of the decimal place those are definitely significant if you can if you think about it you can think about this without actually memorizing the rule could we just write two well sure of course we could just write two that wouldn&amp;#39;t change the number at all so there&amp;#39;s no reason to include this point zero zero zero zero unless you&amp;#39;re doing it for the sake unless you are doing it for the sake of showing how precise you can be that you cannot only just page two this one this one place but you can go all the way out to here and so those are all going to be significant now when you compare that to up here remember I said you can&amp;#39;t just write point five zero four that changes the number so here these are placeholders here these show precision now this next part says trailing zeros aren&amp;#39;t significant unless the decimal point or scientific notation is used so for instance here I had just have four thousand two hundred there is no decimal point after those two zeros aren&amp;#39;t significant and that&amp;#39;s because you can&amp;#39;t just write 42 there and have it be the same number those zeros are just placeholders anytime we have a zero that&amp;#39;s a placeholder it&amp;#39;s not going to be significant anytime you have a zero that isn&amp;#39;t a placeholder like for instance here those are now what if we wanted all of these digits to be significant we can force them to all be significant by putting a period at the end so if we just put a period at the end or a decimal point at the end then that forest is that tells whoever&amp;#39;s looking at your work that you really can measure out to the ones place it just happens to be that in this case both the 10 and the ones place is 0 now what if we wanted just for two and we wanted that first zero to be significant there&amp;#39;s a way to do that to scientific notation is the way to say exactly what want to be significant and what you don&amp;#39;t so in this case we can write out 4.20 and that says hey everything that we have written in the scientific notation that&amp;#39;s significant so if you have it and you have written out in scientific notation whatever is there is going to be significant so if you ever get to an exam it rounds up to something like four four thousand two hundred and you say but I need three significant figures how can I write that down how can I get that point on the test well it&amp;#39;s going to be by going through and putting it into scientific notation so that I know that you know that is three significant figures now the next part of this is how do you do calculations with these because of just being able to count how many scenes he figures you have is great and for something like taking a measurement that would that would be fine but you also you&amp;#39;re going to be doing actual calculations you&amp;#39;re going to be plugging things into equations maybe something that has three significant figures and something that has four significant figures and you need to know how many come out at the end so there&amp;#39;s two different sets of rules there&amp;#39;s rules for if you&amp;#39;re doing addition and subtraction and they&amp;#39;re all sort of you&amp;#39;re doing multiplication and division so for addition and subtraction you use the lowest number of places or decimal points so you&amp;#39;re not actually going to be counting significant figures as we&amp;#39;ve just talked about on the previous slide for addition and subtraction so for example let&amp;#39;s say we&amp;#39;re adding on point two four so something with a once place in a tenth place and something like point three four five where you have a one up to the thousandths place you round this to the lowest number of decimal places so in this case two decimal points or two decimal places and so you would round it to point five nine you&amp;#39;re not counting significant figures here you&amp;#39;re counting decimal places so what if you don&amp;#39;t have a decimal what if you&amp;#39;re just sitting in the higher numbers well in that case you just round to the number of places so here we&amp;#39;re all the way out to the ones but here we&amp;#39;re only at the hundreds so when you round this you round to the nearest hundred and so you end up with forty five hundred so that&amp;#39;s for addition and subtraction you&amp;#39;re not counting sig figs just play whether that be decimal places or places before or to the left of the decimal point with multiplication and division that&amp;#39;s where you&amp;#39;re going to bring in all that significant figures that we did in the previous slide so for multiplication and division you go to the lowest number of sig figs so if we look at 23 we can see that there are two significant figures if we look at 436 we can see that there are three significant figures so when we want to round this we want to round to what there are two significant figures now if you go ahead and plug this into your calculator for me real quick you&amp;#39;ll see that when it rounds we end up with a 1 and a 0 and we can&amp;#39;t and you might say well how do I round that can I just put you know 10,000 well you can&amp;#39;t just put 10,000 because that would then have just one decimal or just one place one significant figure and you need to have two so you would say okay well now I have to convert it into scientific notation so that I can put the point 0 there so let&amp;#39;s do another one with division so here we have four hundred and fifty three divided by three point two so sure we have a decimal place here but that doesn&amp;#39;t make any difference we don&amp;#39;t have to pay any attention to the decimals we just go through and count how many sig figs do we have so here we have three and here we have two so when we get all done with that that means that we&amp;#39;re going to have two significant figures and so we&amp;#39;re left with 140 now some rules for how to actually work with these so these are the rules for coming up with an answer that you&amp;#39;re going to turn in and that&amp;#39;s fine if you only have one or one step you can just say okay well I&amp;#39;ve added these two numbers I&amp;#39;ve multiplied these two numbers whichever and go ahead and put it down on the paper but if you have five or six different steps you&amp;#39;re taking an answer for one equation and filling in another equation now you have to kind of keep track of this it is not a good idea to round at every single step that introduces a little bit of an error every single time and there&amp;#39;s a good chance that you&amp;#39;ll start getting answers wrong especially on you know sort of on line systematic homework so what you want to do is you want to hold out a few decimal points to be honest when I I just keep them my calculator and second answer the whole way through if you want to write about that&amp;#39;s fine to just write out a couple points past the significant figure the last thing event figure then you might say okay well how am I supposed to keep track of what&amp;#39;s going on then how can i if I take the answer from one equation and I add all these extra sig figs how do I know how many sig figs I have there just put a little underline under the lasting fan one and then you&amp;#39;ll see this when I start doing some work but every time I get done with an answer that I need to use someplace else I put a little underline under the last significant figure so I can keep track of it so that&amp;#39;s some kind of hints for actually going about doing this and you know real problems okay so that&amp;#39;s one of the most basic things that you&amp;#39;re going to have to know to do every single calculation problem in this class now the next set of things that you&amp;#39;re really need to have a good background on is something called dimensional analysis or conversion factors and these two are sort of very much interrelated to each other the idea with a conversion factor is you have something that says this much is equal to this much of something else so 100 centimeters equals one meter that&amp;#39;s a conversion factor now the way we use this is through something called dimensional analysis it&amp;#39;s one of the main ways anyways where you can go through and you can convert one item into something else using conversion factors the easiest way to do this is to actually go through and do a few example problems and so that&amp;#39;s what we&amp;#39;re going to do all right so we have your worksheet that you&amp;#39;ve printed off from the internet and we started out by saying the average speed of helium at 25 degrees is twelve hundred and fifty-five meters per second and I say convert that to miles per hour so the way that you want to always think about conversion factors is writing down what we have and write it on what we&amp;#39;re trying to get to and seeing what you need to do in between so we&amp;#39;ll start by writing down what we have so we know we have this and we know at the end of the day we need to have miles per hour so now how do we get between them using only conversions that we know or can easily look up I ask you to memorize all of the metric conversions I don&amp;#39;t care about the other conversions I would give them to you the metric ones you have to know so if we have meters on top we need to do something to get rid of meters having something in the numerator is saying that you&amp;#39;re multiplying it so the opposite of multiplication is division so we put that on the bottom and we know that we can get from meters to miles through using some sort of conversion factor that we either look up or have memorized more likely look up and so we&amp;#39;ll put miles up here now we go when we find that conversion factor and we say well for every one mile there&amp;#39;s 1609 point three meters when you look up these sorts of conversion factors that aren&amp;#39;t nice round numbers it&amp;#39;s not something like in the metric system where you have one in ten and a hundred and a thousand you want to keep one place more than or one significant figure more than what your actual number that you&amp;#39;re starting with is so if we think about how this cancels we now would have miles per second if we keep track of all or all of our units we don&amp;#39;t want miles per second we want miles per hour so now we have seconds on the bottom and we want to get rid of that so that means we have to put seconds on the tops to cross that out and we want hours on the bottom so we&amp;#39;ll do this and then we fill in this conversion factor of course this would be one that you&amp;#39;d be expected to know and if you didn&amp;#39;t remember that off the top of your head you know how many seconds are in a minute so you could convert to minutes and you know how many minutes is in an hour so you can convert to hours from this point now we can look and we can see that our meters cancel and we can see that our seconds cancel and we can see that we have miles per hour so our units are all set which means our answer is going to be fine and we can do 2807 so you can see that that&amp;#39;s much easier to figure out how to do than to try to memorize well am i multiplying by this conversion factor am i dividing by this conversion factor what am i doing so this way you can just trace your units around okay we have one more of these to do see how many minutes does it take light from the Sun to reach Earth given that the distance from the Sun is 93 million miles and the speed of light is 3 times 10 in the m/s or 3 times 8 meters per second okay so to do this one now this one I&amp;#39;m kind of asking you a real question but it really turns out to just be a bunch of conversion factors put together if we know that we have a certain amount of miles and it&amp;#39;s 93 million which means it&amp;#39;s 93 times 10 to the 6 and now the end of this we want to get to time so we need to trace through all the conversion factors that we can find in order to get this well we can start by saying we have we have miles here and we know our speed is in meters per second so we have a distance here and we have a time that&amp;#39;s going to be a good way that we can go through and try to get to time but it&amp;#39;s not going to work with miles so let&amp;#39;s change miles into meters and we&amp;#39;re going to do that the same way that we did here now notice on the second problem though if you look back to your first one the the ordering is flip-flopped and that&amp;#39;s because we&amp;#39;re converting from miles to meters instead of 4 meters to miles so we can write in those numbers and you can also hold off and write in all the numbers at the very end - so now we know that we have meters on top and our miles cancel out and we can look at what else we can do we want to get from a distance to a time so we need something that has both distance and time in it now from there we need to decide well we&amp;#39;re going to multiply by this number or are we going to divide so again we trace through our units we have meters on top and we don&amp;#39;t want meters so we divide by it so that leaves us with seconds on top which is what we want because that&amp;#39;ll end up with our time in it so now we fill in our numbers the number here goes with the meters because it&amp;#39;s on top three so three point zero zero times 10 to the 8th and we put one second here now at this point we want to look at what I had asked you for so we could do this in seconds if we wanted but I had actually asked for minutes and so at this point we can see well we have seconds so we need to convert that into minutes and we know that we have 60 seconds in one minute so that gets rid of this unit leaving us with minutes which is what we wanted and we can solve for that now it&amp;#39;s time to take a look at our significant figures here for both of these so now we have them both up now notice on this one I put I left it as four significant figures now I need to go back and say okay for all of these calculations did we do this right we started with four significant figures here we divided by five here and we did that on purpose all right we looked up that number and we said okay well we have four significant figures here I need to keep one extra now what about this one that 3,600 does that mean that we should round 228 or 2800 well no whenever you have a definition you don&amp;#39;t run into that so there is exactly 60 seconds in one minute there is exactly 60 minutes in one hour there is exactly 3600 seconds in one hour it&amp;#39;s defined that way and so you can think of it as being infinite significant figures however many you need there to be so that means that this is going to be left as 4 because we started with 1 now when we come down here we started with 2 here we again look this up I put it as 5 basically just because I had that number handy but you could have got rounded it to 3 if you had wanted we have this number which has 3 significant figures and then we have this one which looks like 1 but remember it&amp;#39;s a definition and so because of the definition it&amp;#39;s actually infinite and so the only thing that matters for our significant figures is the 93 so we have two significant figures here and so we need to have two significant figures here okay so that sort of walks us through some of the calculations that we&amp;#39;re going to be doing in a very general format where you don&amp;#39;t need to have a lot of chemistry background yeah you&amp;#39;re you can always use dimensional analysis and looking at the units and crossing off the units as a double check whenever you go to do anything so every problem that you do you should write out all of the units all of the time and then each time go through and look at where they are and look at how they cancel and make sure that at the end you have a unit that makes sense if you&amp;#39;re measuring distance and you come out with a unit of time you did something wrong if you&amp;#39;re measuring you know velocity and at the end you need to have a velocity and you come out with something like meters and note second per second you did something wrong so this is a great way to go through and make sure that you did everything okay we&amp;#39;ll get to we&amp;#39;ll get to times later on in the quarter where we have a constant that has tons of different types of ways of writing it in and all of the differences are with units how do you know which one to use you can memorize it and you can say well when I use this equation I&amp;#39;m going to use this version when I use this equation I&amp;#39;m going to use this version or you can just look at the units and say okay I know I have liters and atmospheres so I&amp;#39;m going to use this version of our or I know that I have joules so I&amp;#39;m going to use this version of our things of that sort okay so now we&amp;#39;re going to get into the structure of an atom and we&amp;#39;re going to do this at a really basic level right now and then chapter one we&amp;#39;ll get into it in much much greater detail and in some ways I&amp;#39;ll tell you that we lied a little bit here so this is the Bohr model of an atom and I like to sometimes call this the high school model this is sort of the first model that we teach you it has some very good uses some of which we&amp;#39;re going to take advantage of here starting this classroom next but it also isn&amp;#39;t a hundred percent accurate but it&amp;#39;s a good starting point so we&amp;#39;ll kind of start from there here you can think of it as being a nucleus in the middle that has two different parts of it it has protons and it has neutrons the protons have a positive charge the neutrons have no charge at all and then around this nuclei going in right now we&amp;#39;ll think of it as rings and later on we&amp;#39;ll expand that a bit that you have electrons and those electrons are negatively charged so there&amp;#39;s some things you want to be able to look at a periodic table and calculate pretty quickly without having to put a huge amount of thought into so if you don&amp;#39;t know how to do this is fine but you want to go get some practice at it so if you have the number of protons you have and you subtract the amount of electrons your protons do I have a plus 1 charge your electrons have a minus 1 charge so that&amp;#39;s going to give you the charge of the ion now in any sort of neutral compound this is the third atom that&amp;#39;s 0 because you&amp;#39;re going to have the same number of protons electrons but you can also start adding and subtracting protons and electrons as time goes on and making ions out of them and we&amp;#39;ll talk about that in much more detail too so keep this in mind that your charge is always going to be equal to your protons minus your electrons now if you look at your periodic table there&amp;#39;s a bunch of different numbers that you can you can deal with one of them is your atomic number that&amp;#39;s your number of protons and then there&amp;#39;s also an atomic mass an atomic mass is your number of protons plus your number of neutrons and so you can take those and you can add them up and that gives you your atomic mass because you&amp;#39;ll always have a periodic table you&amp;#39;ll always know your number of protons you&amp;#39;ll always know your atomic mass for any sort of exam or anything like that and what you&amp;#39;ll see is a lot of times will King calc back calculate and figure out how many neutrons we have we can take your mass and subtract your protons and get your neutrons and we&amp;#39;ll do that a lot in one scene when we start getting into a nuclear chem now you really have to remember these charges which ones are positive and which ones are negative and in order to help remember that we have a little joke lots of great and simultaneously horrible chemistry jokes out there this is one of them so you have two neutrons and they walk into a bar in the order a couple of drinks as the one about is about to leave the waiter says how much does it cost and Neutron set or in the let me start over okay a neutron walks into a bar orders a couple of drinks as she&amp;#39;s about to leave she asked the waiter how much and the way to reply is for you no charge that&amp;#39;s the joke to sort of remember what a neutron is we have another one here and this one is one of the most famous one that gets repeated over and over and over again and you have these two different atoms and they&amp;#39;re talking to each other and the one says I&amp;#39;m hit im hit I&amp;#39;ve lost an electron and the other one says are you sure and the first one says I&amp;#39;m positive they lost an electron and so they&amp;#39;re positive right so two two nice horrible jokes for you to remember these by lots more of these as a quarter goes on okay so now comes some sort of time for just general definitions so first of all we have something called an isotope what is an isotope so anytime that you have the same number of protons but you have a different molecular mass that&amp;#39;s an isotope and the reason why you get this is because you have different numbers of neutrons and so your neutrons within one particular atom can change and without really changing too much of the properties we&amp;#39;ll see again in one see that some of the properties definitely change the mass definitely changes because you&amp;#39;re adding in a neutron which has it has a mass of about one but most of its properties are very similar now why are the molecular masses on the periodic table of decimal points so you should probably always have a periodic table handy in this class just kind of sitting out starting next class you probably want to do that there&amp;#39;s you know they&amp;#39;re around so whenever you look at this you&amp;#39;ll see that your molecular masses are decimal points and why is that well the reason for that is that they&amp;#39;re actually going to be an average they&amp;#39;re going to be an average of both or all of the isotopes of that compound or that atom so something like silver has two isotopes that make it up sometimes you&amp;#39;ll get silver 1:07 if you were to weigh the Mastiff that one Adam you come out with a unit or 107 sometimes it&amp;#39;s 109 so on the periodic table what they do is they do something called a weighted average and you know weighted averages are a good thing to know how to do if you don&amp;#39;t know how to do that reviewed in your math class it&amp;#39;s also how your grades are figured out you know so when you go to figure out your grades and I say figure out a weighted average that that&amp;#39;s what I&amp;#39;m talking about and that&amp;#39;s how it&amp;#39;s that&amp;#39;s how it&amp;#39;s determined here so in this case we would have 107 silver making up 51% 109 silver making up the rest well it will do this out on the document camera in just a minute you&amp;#39;ll notice some of these are even more complicated some of these will end up with two or three different isotopes now the reason we do a weighted average as opposed to just averaging it you may say why can&amp;#39;t I just take this and say well 107 plus 109 divided by 2 well we want to know what the mass of this is we go out into the world and we take some silver out of the you know some silver out of the ground clean it up get rid of all the ore and purify it how much is that silver what&amp;#39;s the molecular mass of that silver and now all of the silver is split 50/50 107 and 109 and this is where the idea of weighted averages come in so we&amp;#39;ll do this one out on the document camera so we can see it all worked out okay so we have 51 point eight three nine percent of silver is 107 so we need to figure out how much of how much there is at each so we know this because the problem says so now we also need to know what percent is 109 well it&amp;#39;s the rest of it so we just take 100 subtract that so this is 100 minus the silver 107 percent which gives us the forty eight point one six one now we do what we call a weighted average so I&amp;#39;m going to do it out in two steps you can do it out in one it&amp;#39;s you find either way so if we know that we have 107 grams of this we can just say that we have 107 grams per mole and 109 of this what we&amp;#39;ll do is we&amp;#39;ll go through and we&amp;#39;ll multiply that by the percent and the same thing here so we&amp;#39;ve taken 107 multiplied it by the percent that makes it up in in nature this multiplied by the percent that makes it up in nature and we get those two numbers and then we add them all and we get that now with everything in chemistry you want to be thinking does this make any sense now in this case we have a weighted average between two things it&amp;#39;s 107 and 109 and it&amp;#39;s about 5050 right ones 51 ones 48 it&amp;#39;s about 5050 so we would expect the answer to be close to what the normal average would be or what the real average is which is 108 so since we have this in this being added together almost equal proportions we want it to be close to 108 with a little bit less because the 107 the lower number has a little bit higher percentage and that&amp;#39;s exactly what we see we see that as close to 108 just a little bit less than 108 so that makes sense based on the averages and what we know about how averages work and so that&amp;#39;s it now this was a case where we only had two Isis hopes that we were averaging you could do this for more something like carbon has one main one and then two smaller ones you could do that for each and you would just do this three times and then add it all up okay so now that we know all these things about atoms we know they&amp;#39;re protons we know there are electrons we know they&amp;#39;re neutrons they&amp;#39;re masses we need a nice way of looking at all this data and figuring things out very quickly and this is where the periodic table comes in we have all the elements arranged in order of increasing atomic number so atomic number remember that&amp;#39;s the number of protons that we have now they&amp;#39;re arranged in these repeating patterns and we&amp;#39;ll get into more detail about exactly how that is but for right now what you can know is that they have the same number of what we call valence electrons outside shells if you think about the Bohr model you can kind of think about they&amp;#39;re those rings right and whether they&amp;#39;re filled or well how many they have in those outside rings and so what happens there is that gives certain columns or groups similar properties so everything that&amp;#39;s going to be in Group one is going to have a relatively similar property to each other now of course there&amp;#39;s going to be differences because the atomic mass here is much much bigger than here the number of protons the number electrons are much bigger and there&amp;#39;s some trends that we&amp;#39;ll be able to pull out of the periodic table later on but for the most part this group would have the same sort of trends as E or the same sort of properties as it struck each other this group same sort of property does each other all the way across the periodic table so if you go down a column you have very similar properties now this happens to be my sort of favorite periodic table that I I carry around and you don&amp;#39;t have all my books I actually replace a lot of my book periodic tables with this one you know find your favorite periodic table from the internet we&amp;#39;re in it out and keep it with you all the time in class and when you&amp;#39;re doing chemistry I don&amp;#39;t really expect you going to the bars with them and such things but keeps them around you whenever you&amp;#39;re doing your homework keep them out in class with you because I&amp;#39;ll refer to them a lot okay now something that we&amp;#39;re going to get into a little bit with naming and this is probably all of the freshman chemistry students least favorite part about this class because there&amp;#39;s a lot of memorization in general I say with chemistry you shouldn&amp;#39;t be memorizing hardly anything if you&amp;#39;re memorizing things you aren&amp;#39;t in general are not learning them um and in chemistry that gets dangerous if you memorize how to do a problem you&amp;#39;re probably going to have problems on an exam because I&amp;#39;m going to give you one that&amp;#39;s a little bit different and if you don&amp;#39;t really know what you&amp;#39;re doing you&amp;#39;re not going to be able to solve it because it&amp;#39;s not going to be the exact same as your homework problems this is sort of the exception to that you have to do a lot in a lot of memorization for the ionic naming it&amp;#39;s a pain just do it you&amp;#39;re going to need it for one B you&amp;#39;re going to need it for one C and you just need it to be around chemistry in general which includes the biology that you&amp;#39;re going to be in you you want to have a good idea of what&amp;#39;s happening you want to be able to look at a compound and name it quickly without having to think about it too much I can test you on this in the first midterm just by saying here&amp;#39;s a name you know give me the formula here&amp;#39;s the formula give me the name I can do it on the second midterm by saying draw me this compound and if you don&amp;#39;t know how to name it you don&amp;#39;t know how to pull the formula out of the name I gave you you won&amp;#39;t be able to do it so make sure you just go through and do all of this so before we can get into naming too much we have to figure out how do we know what type of naming we&amp;#39;re going to do so up here I have we have ionic molecular acids inorganic now we&amp;#39;re going to get very much into ionic molecular in acids those are the ones that your testable on in this course for organic you have a homework assignment on this we&amp;#39;ll talk about it a little bit don&amp;#39;t worry about it too much in general that&amp;#39;s all going to be covered in really great detail next year but you should have a general idea of how it works because I&amp;#39;m going to talk about it I&amp;#39;m gonna say things like methane and ethane and you know ethanol and propanol and you should have some idea of what I&amp;#39;m talking about I&amp;#39;ll also always have the structure up there but you don&amp;#39;t want something like that that to throw you off and so just have a general idea of how it works be able to answer questions on it if you have the book in front of you we&amp;#39;re just not going to get too into it this or this class that&amp;#39;ll be more for next year these three are the ones we&amp;#39;re going to focus on now all of these are going to be named very differently if you have an ionic compound is named completely differently than a molecular compound you&amp;#39;ll learn to like the molecular ones for the naming purposes here and assets are going to be sort of based off the ionic nomenclature but that&amp;#39;s still very different and so before we can actually get into the rules for naming we have to get into how we know which one is which type of compound so to do this we have to talk a little bit about bonding and how things bond so whenever whenever something is trying to bond with another atom it&amp;#39;s trying to do what we call complete an octet now we&amp;#39;ll see some atoms don&amp;#39;t actually do that exactly but they&amp;#39;re trying to they&amp;#39;re trying to get a full octet which means that they would have eight atoms or eight electrons in their outside shell so if you have one atom that has six in its outside shell and another one that has six in this outside shell it can go and it can form a bond now in this case it&amp;#39;s going to want to share those electrons because you have six here and six here so this one can&amp;#39;t just give two of it away or it&amp;#39;s going to have some problems this one can&amp;#39;t just give two of them away or it&amp;#39;s going to have some problems there are times when you can do that when you can just trade electrons and there&amp;#39;s times when you have to share electrons and that&amp;#39;s your difference between your two different types of compounds there are two different types of bonds so for ionic compounds that have ionic bonds they&amp;#39;re going to trade electrons one one atom is going to give away its electrons to the other one so something like sodium chloride so if you take and you look at your periodic table a minute and you look at sodium three here and you look at chloride right here you can see that sodium has one electron it&amp;#39;s outside shell and the periodic table is really nice for looking at this quickly because you can look here and say okay this has one valence electron this has two valence electrons three four five six seven and eight all the way across so we can use this to look and see how many valence electrons we have very quickly so sodium has one and chlorine has seven so they can just trade electrons the sodium will say well I don&amp;#39;t really want one electron sitting there by itself you take it and gives it to the chlorine the chlorine says great this gives me eight so now they both have eight in covalent bonding they&amp;#39;re sharing the electrons so this would be something like carbon and oxygen or two oxygens or two fluorines where they don&amp;#39;t they can&amp;#39;t just give them away they&amp;#39;d still be too short of electrons and so instead they&amp;#39;ll share them carbonyl gives let oxygen take some of them oxygen rule that you know did you solve them and then you count those electrons for both we won&amp;#39;t get too into metallic bonding but it is important to talk about and have sort of in the background now and metallic bonding you have these big networks in these big networks of electrons that can move back and forth between all of them here and here you sort of have the electrons that are relatively associated with one or two groups here they&amp;#39;re completely delocalized which means that you can kind of move them from one side to the other if you do the right sort of thing to it and we call this you know a wire right we can take a wire and we can stretch it out that&amp;#39;s all metallic bonds we can put electricity through it and the fact that you have these delocalized electrons that are going across this entire group is what would what allows that to happen and those are for metallic bonds but these are the two we&amp;#39;ll be focusing on for the sake of naming okay and one last thing we need to talk about here is something called empirical versus molecular formula now this comes up in covalent bonding not anionic so keep that in mind you may even want to write that down this is just for covalent issues with ionic compounds we&amp;#39;re always going to listen as the lowest whole number ratio so we would never say ng 2 O 2 or na 2 CL 2 we always want to reduce them down to the lowest amount with covalent bonding that&amp;#39;s not necessarily how things work something like hydrazine if you look at this we have n 2 H 4 and you could say well can I reduce that down to NH 2 well you can&amp;#39;t because it changes the whole compound n 2 H 4 is not the same thing as NH 2 so we have to have some nomenclature for this that we&amp;#39;re going to refer to from time to time so we have an empirical formula which is our lowest whole number ratio doesn&amp;#39;t actually tell us a lot about the molecule itself but it does tell us how many of each atom are in the substance and then what the molecular formula is going to tell us is it&amp;#39;s going to go through and say well this is how this is what the molecule actually has in it one molecule hydrazine actually has two nitrogen&amp;#39;s and four hydrogen&amp;#39;s or ethane two carbons and six hydrogen&amp;#39;s now we&amp;#39;ll do some examples using this where you can see that we can find the empirical formula fairly easily experimentally and we can find the molecular mass fairly easily experimentally which is why one of the reasons that this is so important to have these differences here so that goes into a little bit more of covalent bonding definitions now I&amp;#39;ll spend some time on ionic bonds and then we&amp;#39;ll learn how to actually name them so this is the day filled with bad jokes so we have another one so the way that ionic bonding works is by the fact that these atoms will trade electrons and when you trade electrons electrons have a negative charge and so there&amp;#39;s going to be a charge development if you trade electrons like that so we have you have this teacher up here and you have these little atoms here all these positive ions since perhaps one of you gentlemen wouldn&amp;#39;t mind telling me just what it is outside this window that you find so attractive so remember positives and negatives are always going to attract each other right so if you take an electron you take it away from one atom you make it a positive charge you&amp;#39;re taking a negative charge away you&amp;#39;re making it a positive charge you&amp;#39;re giving it to another atom which means that that atom is going to be a negative so you have a positive atom now and a negative atom those two are going to attract just like a magnet would and that&amp;#39;s how you form your ionic bonds so how do we actually write this out quickly well we do this we can do this this way where we have ionic bonding here we take something like potassium and if you look at your periodic table you&amp;#39;ll see that potassium has one electron it&amp;#39;s in that first group and so it has one valence electron if you look at iodine so you&amp;#39;re you know you&amp;#39;re looking at your periodic table you&amp;#39;re finding it on the periodic table you see iodine is in the seventh group so it means it has seven electrons so how can we get this so they both have a full octet well we&amp;#39;ll take the electron away from potassium we&amp;#39;ll give it to iodine when we do that potassium develops a plus charge you&amp;#39;ve given away one of its electrons iodine has developed a negative charge because you&amp;#39;ve given it to iodine and so you get this structure where you form the positive and the minus they attract and they form potassium iodide the exact same thing can happen where now instead you have to give one electron away to two different atoms so if you&amp;#39;re trying to combine something like magnesium along with something like fluorine now you have an issue where you have two electrons in magnesium outside shell and fluorine only can take one well you just take double the amount of fluorines so now magnesium says okay I&amp;#39;m going to give you one electron I&amp;#39;m going to give you an electron both of the fluorines develop a negative one charge the magnesium gets a +2 charge and they all tracked each other and they form this structure which means that then you would have ngf 2 1 mg in two fluorines now that&amp;#39;s how you want to know what what&amp;#39;s going on and how these are treating whether they just trade one and become k+ and i - in this case or sodium chloride would be the same same form or whether you have MGF - it&amp;#39;s all about the charges and making sure that the charge is balanced now there&amp;#39;s a quicker ways of doing this though than trying to write this out each time and think about exactly where the electrons are moving around each time so here&amp;#39;s a helpful trick to remember it so you can kind of take the charges and you crisscross them now you might be saying how do I know what the charges are basically through memorization and we&amp;#39;ll get into that in just a moment so if you write down the charges here and the charges here and you know that your ions have these charges you can crisscross them down you can say well I&amp;#39;m going to Chris I&amp;#39;m going to move this down to the oxygen I&amp;#39;m going to move this down to the aluminum now what that ends up doing is it gives you a compound where your charge is balanced you can say okay aluminum has a +3 charge and I&amp;#39;m going to multiply it by 2 now that it means I have plus 6 oxygen has a minus 2 charge and that but there&amp;#39;s three of them so minus two times three that&amp;#39;s minus six so now you add up here plus charges and your minus charges and they need to equal zero and in this case you see that they do so this is sort of a helpful trick for getting you to this neutral compound faster you want your ionic compounds to be neutral there is one major caveat to this though that you have to watch out for if you&amp;#39;re going to use this little quick trick and that is that goes back to this idea of empirical formula and molecular formula and how that&amp;#39;s only true in covalent we only deal with that in covalent ionic always need to be the lowest whole number ratio what if you have something that had the same charge and it isn&amp;#39;t one or same magnitude a charge I should say and it isn&amp;#39;t one something like magnesium that has a plus two oxygen that has a minus two you crisscross them down you form mg - OH - that&amp;#39;s an ionic compound you have to have the lowest whole number ratio so this isn&amp;#39;t okay so you need to then reduce down to the lowest whole number ratio so when you do sit down it becomes MgO so at that so whenever you have this sort of situation and you&amp;#39;re you could probably just say okay well these are the same charge so I&amp;#39;m going to say that that&amp;#39;s just NGO but if you didn&amp;#39;t catch that right away you did do the crisscross trick and you saw that this is mg 202 you have to reduce that down now something that we are going to just sort of show you and then move on with is that these form these big crystal lattices and 1b when you first start 1d this is what you&amp;#39;re going to start with and you&amp;#39;re going to learn all about these different shapes in these different forms and you&amp;#39;ll put names to them and all of that and for this class I just want you to know that this exists that when you get these you don&amp;#39;t have one sodium chloride it just stuck together and you have this one little out of the sodium chloride all by itself what you actually have is you have these crystals if you go to you know your pantry and you pull out salt you actually have all these little crystal lattices inside of it and that&amp;#39;s what&amp;#39;s forming so just keep that in the back of your head that this is what these ionic compounds look like okay now how do you know what the ions are so I&amp;#39;ve said that it&amp;#39;s memorization that wasn&amp;#39;t really a hundred percent true so you can look at the periodic table and you can find out what the charges are for the most part there&amp;#39;s there&amp;#39;s some exceptions here but for the most part so if you look at this first row we have one valence electron and you want to find a way to get rid of that so you can go through and you can just take that one electron off giving it a plus one charge or you can take two electrons off from this group giving it a plus two charge this group you would have three valence electrons so you take three off when you start getting into this group now it&amp;#39;s not really going to be able to just gain - or loose there excuse me gain four or lose four as easily so those aren&amp;#39;t going to be big on forming ionic compounds at all when we&amp;#39;re to the right side of the periodic table we look at here how many valence electrons does that have well it has seven what&amp;#39;s going to be easier taking away seven Tron&amp;#39;s or just adding in one well of course adding in one would be easier and so because of that you&amp;#39;re adding an electron you&amp;#39;re adding in a negative charge and so it&amp;#39;s going to be a negative one if you look at this row you have six valence electrons it&amp;#39;s in group six Eve six is it going to be easier to plus six or at into it&amp;#39;s going to be easier to add in two and so you get a negative two charge same thing here easier to pull off five or add in three will add in three so that&amp;#39;s going to be a negative three charge this section in here your transition metals in this little group right here for right now you pretty much just have to memorize them after we start talking about electron configurations in more detail and how to go about dealing with those and seeing where electrons are removed from will actually be able to explain most of them however for right this moment there&amp;#39;s really no way to explain it easily so these groups you just have to sort of memorize and when we get into check the very end of chapter one we&amp;#39;ll learn why all of those are now I do want to help member help you memorize one of this section so this little group right here we&amp;#39;re going to sort of pull out and we&amp;#39;re going to look at in more detail so there&amp;#39;s something called the inert pair effect and I don&amp;#39;t want to go into exactly why this is at the moment um if you&amp;#39;ve had a lot of chemistry and you want me to explain it I can do that later but for now we&amp;#39;re just going to leave it as this is how it works and then at the very end of chapter one we&amp;#39;ll go back and we&amp;#39;ll explain it using electron configurations so for right now you can notice though that these have these groups of 1 3 2 4 3 5 so they&amp;#39;re always off by 2 you can form this top lower ion or you can form this bottom ion and they&amp;#39;re always off by a factor of 2 so use this to help you remember it for right now and we&amp;#39;ll explain why it is later on ok now we&amp;#39;ll finally be able to get into naming these so for here a lot of these listed and there&amp;#39;s copies of all of these sorts of things online this is from a different book but we&amp;#39;ve pulled out all of the ions and put them online for you so the idea to get out of this and the lists online is that there&amp;#39;s also all of these polyatomic ions that we need to talk about those for the most part are going to be memorization but there&amp;#39;s some hints for memorization so everything that I&amp;#39;m about to say we&amp;#39;ve also put into an online study guide that is available um so that you can kind of go through and see what I&amp;#39;m saying when I say eight and i&amp;#39;ts because it&amp;#39;s a little bit hard to hear so these are lists of things that you effectively need to have memorized but there&amp;#39;s tricks to memorizing it that will make life a lot easier so there&amp;#39;s these two these different types of endings and these different types of prefixes so you have eight sites and IDEs as your endings if you have something with an ID ending that is just the compound nut or the atom on its own something like phosphide or sulfide or oxide if you have something with an eight or a knight ending like this that&amp;#39;s going to be your oxygens so something like phosphate or phosphite are going to have oxygens on the end and the ice in the eight refers to how many oxygens or it&amp;#39;s oxidation numbers so what we&amp;#39;ll do here is whenever you have is you should memorize one version of these you memorize all of the eights or you memorize all of the ice you don&amp;#39;t memorize both if you have something with an eighth ending that&amp;#39;s what I happen to memorize when I did this back in high school um or college and I memorized through and I memorized ha State and carbonate in sulfate and then I knew that every time that I changed that to a night ending I just took away in oxygen so if phosphate is po4 three 9s phosphite is po3 three - okay so that&amp;#39;s kind of your hints for doing this now you&amp;#39;ll also see times where you have something like if you look at iron iron has two different oxidation states two different charges so three plus and a two plus and we have a different nomenclature for certain compounds for instance iron where we call it ferrous or ferric and those us in ache endings those refer to the charges if you have an ache ending you would have a three plus charge if you have an us ending you would have a two plus charge the us always refers to the lower charge the it always refers to the higher charge and so keep that in mind when you&amp;#39;re memorizing those weird named ones like iron and lead is another one Stannis and static 410 so there&amp;#39;s these groupings of ones that have two different names one comes from the original Latin root the other one is the name that we know it by and these are pretty easy to pick out of the periodic table because they&amp;#39;re the ones where the element symbol doesn&amp;#39;t really match up with what we know we know that iron does is Fe we know that tin is SN and so those are pretty easy to pick out of the periodic table and I have those highlighted on the study guides as well so make sure you go in you know start working on memorizing those and start working on making sure that you can form those ionic compounds using the ions that you have memorized because again you&amp;#39;ll be tested on this all through general chem and you better just it&amp;#39;s better to just do it now and get all the points starting now rather than waiting till the end to do it next class we&amp;#39;ll get into how to name acids and how to name covalent compounds which are significantly easier than this just because there&amp;#39;s a lot less memorization to it um if this didn&amp;#39;t make a huge amount of sense you know make sure you go and look at the study guide online where it&amp;#39;s all written out with the owe us AAT e and ite endings to help you

Transcript for:General Chemistry Lecture Notes

Transcript for:
General Chemistry Lecture Notes