we will go ahead and get started so what we’re going to do is finish up chapter four okay fix it whatever we’ll finish up chapter four so you’ve got that homework that’s posted I’ve given you enough homework to probably get through all the material we’re going to talk about today and then hopefully I’ll have more homework for tomorrow which will cover some new stuff so thursday we looked at atomic notation how we end up representing individual elements may your textbook does refer to this as atomic notation think it’s a little bit better to refer to it as nuclear notation why what reference within that symbology tells you anything about the electrons nothing to tell you about the electrons in your outfit right which means we don’t we don’t care about the electrons all we’re really focused on with this notation is just the nucleus okay we can interpret some information about the electrons by taking a guess at it but it turns out that notation really doesn’t give us that information alright anybody that’s seen some further information where do we find information about the number of electrons could look at the number of protons but that doesn’t guarantee it as we’ll see later in the semester upper right hand corner tells us about our charge that’s going to give us information about the number of electrons within that individual molecule or element okay and we will see that uh before exam two I don’t know when exactly but we’ll see that come up as pretty soon all right then we’ve got our periodic table I which organized all of this information so that we could then find it and kind of look at a new organization for it so we’re used to seeing the periodic table in theory now at this point in the current format that we’ve dealt with but that wasn’t the original beginning point port remember we put up Dalton’s old experiments or his notations for his theory he only had to deal with something like 20 different elements and he had a slightly different order than what we currently have didn’t have it nice and shaped out okay so where did this shape in organization come from and that was ultimately trying to find different comparisons with our patterns within the elements hi sorry I thought we were there we aren’t there yet yeah we’ve got to talk about isotopes so when we looked at our notation and gave us information about the protons the protons do what what information does that tell us okay they define the element that we’re going to be working with so if you have four protons you know the element you’re looking at is beryllium okay or you could cheat TBE what happens we look the number of neutrons that’s really going to determine our mass for the individual elephant elephant it’s early right define our element ah sorry elephants were completely wrong elephants don’t even rhyme with matts define our maths I our protons and neutrons contribute but our protons can’t change once we’re looking at an individual element the number of neutrons can potentially change and that’s how our mass changes alright the other thing we could look at is instead of looking at defining the mass for an individual element we can then separate it into a different category and we can look at it as defining what is known as the isotope hi your isotope is the same element it just has differing numbers of neutrons since those neutrons don’t contribute a charge a lot of the chemistry of that element is the same it does change some minor effects but for the most part we see the same reactivity we’ve seen sort of the same general properties for that compound or that element so what’s happening when we look at an isotope all atoms like we just discussed have the same number of protons rubber our protons define the element if we go through and look at the individual

elements though particularly if we look at the molecular weights or sorry atomic weights of each of our elements you’ll notice that they don’t come out to whole numbers there is some variation off of the whole number and when we’re totaling we’re just looking at the number of protons and neutrons within so we should expect to see a whole number and we don’t for a lot of the elements so why do we not see that whole number that’s because what we’re reporting on our periodic tables is the average atomic weight for that particular element okay so some elements have more neutrons or less neutrons that changes the wait for our mass and we end up getting a different mass element to account for that weight or to make sure that we report we show that in a weighted average that shows up on our periodic table yes the electrons or what wait contribution one 1827 yeah if you add a lot say like a hundred you’re now getting up close not even close if you had a hundred electrons okay that’s now a hundred over 1826 that’s getting more but it’s not that big of a weight contribution okay so even when we push up to the higher elements the weight contribution of our electrons is still relatively minor it does contribute if you shift out far enough decimal places but in most cases that you guys are going to be working with this semester the electrons don’t contribute to it the overall maths so we’re concerned about our protons and neutrons so our isotopes are the same element but have different masses because of differing amounts of neutrons in them all right so one of the big classic examples which is actually relevant for organic chemistry we can look at hydrogen I had the most common isotope for hydrogen is hydrogen one any guesses why it might be hydrogen one how you might know that it’s the atomic weight of hydrogen reported as one okay which means when we look at a weighted average there’s not a whole lot of something in there that has a higher atomic week otherwise when we looked at our average you wouldn’t be exactly one hi turns out that we can add another Neutron to a hydrogen element or the hydrogen atom and we can make it deuterium right it gets a special name in this case because it’s commonly used particularly in organic chemistry so the more common isotopes we have to work with as far as chemistry goes typically pick up an extra name right how else could we refer to it without having to know that extra name because that could be a bit td’s some of these have two or three different isotopes and we had to name all of the elements on here and then name all of their isotopes on top of it it’s going to be a lot of effort how could we write it out so that we know what we’re looking at a couple of big ways that we could do it one we could look at the symbols and you’ll notice what I’ve circled here is the max bringing in that tube now says we’re looking at a different atomic mass for the hydrogen element okay but if we had to then speak that to somebody when we say 1 superscript H okay or superscript 2 H it’s a bit tedious to go through and say so how could we actually refer to that mass well it’s our hydrogen element with maths one or our hydrogen element with mass too high we typically don’t refer to hydrogen to as hydrogen too because we have that other name for deuterium all right another common are not common isotope but another isotope of hydrogen any guesses what do you think we could refer to it as another neutron there we go hydrogen three yes it does it does how many neutrons does a hydrogen atom house hydrogen has zero neutrons a hydrogen

atom does not have any neutrons deuterium has a neutron why did we add neutrons to begin with okay neutrons contribute to the mass but why did we need that mass in there remember we said there was two reasons why we could postulate the existence of a neutron mass was one what was the other reasoning repulsive forces within the nucleus okay if we take a look at hydrogen how many protons are there one what’s the repulsive force within the nucleus is there any positive positive repulsion no there’s nothing to repel against why do we need a neutron you don’t all right what happens when you move up to healing so now what happens when we move to helium we now have two protons what happens we bring those positive charges very close to each other they repel we now need some kind of glue or neutral feature to keep those two positive charges connected to each other how do we do that now we bring in the neutrons okay and what you were talking about before Thor was that one-to-one relationship between protons and neutrons that holds true for everything above hydrogen and even then once you get too far up it stops starts to fall apart all right because if we get further and further into our radioactive isotopes we have to add more neutrons then we have protons because the proton repulsive forces start to contribute too much all right so hydrogen and it’s of most common state has no neutrons it’s just that proton I am officially an electron when we move to deuterium what’s happened how many protons do we have still one why only one what happens if we made it to so we made it to its not the element okay so it’s still one proton how do we get that mass of two we have to add effectively the same mass as a proton without the charge would we do that with a neutron what happens when you move up to hydrogen three how many protons do we have has to be one to make up the rest of that mass what do we need we need two neutrons yeah all you add our neutrons exactly right if we add do we change the number of protons it’s no longer hydrogen we can only change the number of neutrons so when you’re moving within isotopes the only thing changing within an isotope is the number of neutrons yes yes and no so no there’s not a theoretical limit we can jam in as many neutrons as possible yes what ends up happening is eventually decomposes and falls apart and that’s what accounts for the radioactive elements we’ve got so many different things in there that eventually just falls apart okay which is why when we look at the isotopes for hydrogen we only end up with really three we end up with our standard hydrogen one we get hydrogen to hydrogen three is pretty much the last one that I’ve ever heard of and if we tried to jam in a fourth neutron we probably could jam it in there but then eventually it would quickly spit itself back out because there’s no need for it hi any ideas on a name for hydrogen three other than hydrogen three try because we’re looking at a mass a larger mass along looking at oof anybody know how to spell that properly good didn’t say that’s right ah tritium alright so we’re looking at hydrogen three we’ve now added two neutrons to that structure alright so are isotopes are just changing the number whoops don’t look at that how many protons and neutrons is an atom of lead 206 have what’s our first thing that we’re going to have to do identify our element on the periodic table lead has what symbol hi where’s the 206 go in our notation 206 what’s the last piece of information we would need we need the number of protons so our atomic number so we find

lead on the periodic table it’s 82 which means the number of protons are careful what says 207 so we look at lead there are two numbers up there 82 and 207 what is 207 stand for you’ll notice writing them oddly here 207 according to our key represents the atomic weight not the atomic number the atomic number is your number of protons so you’ll notice vital don’t ask me why they swap the order on what they did so our number of protons is how many to figure out our number of neutrons neutrons plus protons equals to 0 6 neutrons + 82 equals 206 our neutrons equal 206 minus 80 to go if you look any but it’s Annie all right questions about that so we’ve got to be careful when we’re saying bottom in top we take a look at that element again if I’m going to write out the atomic notation I get PB 206 82 in the atomic notation what is 206 our atomic mass what’s the 82 our atomic number when we shift the periodic table and we look at the numbers on our periodic tables let’s go ahead and draw this in here we’re saying it’s our box on our periodic table we let in the middle I don’t know why I have to look it up but I’m doing 82 and then to a 7.2 what’s the number on the top it’s our atomic number okay so top versus bottom you have to be careful with right the top in our atomic notation is our atomic mass when looking at the periodic table in most situations your atomic mass is at the bottom of the symbol again I have no idea why they do that all right how can you make sure that you’re comfortable with that one memorize the atomic notation that format you will get directly tested on the next part is how do you get that information from the periodic table well potentially the periodic tables could change so that can make it more difficult okay but you know you need the atomic mass in the atomic number okay so if you’re looking at a new periodic table how can you tell which ones which look at the key or the legend on the periodic table to give you that information so in our case we’ve got a key with bromine in it pointing to our atomic number and our atomic weight I or our atomic mass right make sense so be careful with how you’re looking at that make sure you’re you’re watching out for those kind of simple mistakes next part of this is recognizing what happens when we look at our atomic weight on the periodic table and the atomic weight is not that whole number that we looked at with our isotopes it’s slightly different than that for hydrogen it’s darn close to exactly one but it still says 1.01 Louise at all it’s just a estimation issue that may be the contribution of the electron it’s not but let’s pretend it is all right what happens when we move up to lead we jump to lead it’s now 20 seven point two point two is not point one that’s a pretty big jump there why is that happen and we haven’t added enough electrons to make it a point to write or for mercury it says point five nine how can we get that point 59 contribution your periodic table does not give you the atomic weight or mass of an isotope it gives you the atomic mass for the element okay when we look at an individual sample for an element some of it is one atomic weight summer saw the atomic weight some of it is another because you have differing neutrons within the same group of elements unless you go through and purify and separate the isotopes away from each other okay what you’d have to look at is an average a molecular atomic

weight all right so what we’d be looking at is your simple versus weighted averages and most people are comfortable with simple if we’ve got two things not sure I can come up with a quick example like that simple average we just look at the part over the total all right when we look at a weighted average we now have to take into consideration how much does that particular thing contribute so when we look at grades for instance your homework contributes only ten percent of the total points in your final grade if we look at its current value as far as points it’s worth a little bit more than that okay because we’re only looking at the total possible we aren’t looking at how much it’s supposed to contribute that’s where our weighted averages come in we take a look at say hydrogen we have some elements so our atomic mass we have hydrogen with an atomic mass of say 1 but then we also have the atomic mass of deuterium and the atomic mass of tritium contributing to this and we divide that by our total possible or are three but within say three molecules actually change that three let’s make it a hundred so let’s take a look at a hundred Adam sample if we just look at the isotopes one two and three as possibilities what we’re saying is that each of those is contributing equally to our total atomic max turns out that’s not the case okay within a sample that has a hundred atoms it’s probably something on the order of 99 of them have an atomic mass of one okay after that now we kind of run into problems because I said numbers instead of percentages so let’s say 98 have an atomic mass of 11 has an atomic mass of 21 has an atomic mass of three now when we go through and calculate we would get a much more accurate representation of the atomic mass of that whole solution what we’ve done is looked at a weighted averages or the percent contribution per each of those isotopes to go through and do this let’s see if we got an example here if we wanted to figure out the average atomic mass for gallium okay so what we want to do is the same general ideas we did before try and figure out what our atomic mass should come out to be so first off do we know what the answer is it is 69.7 to how do you know that will say atomic mass how do you know it’s 69.7 to periodic table tells you okay so what we now have to do is see how that number was calculated so what we would go through and do is look at our mass contributions hey there’s two isotopes gallium 69 and gallium 71 okay gallium 69 contributes a mass of 68.9 to 6am us and our ozl 171 contributes 70.9 25 if we just looked at this as an average and we now just divide it by those two possible elements do we get 69.7 to anybody do that calculation so we want to add the two numbers first and then divide by two what do you guys get so too early well I did you already get the average 70 point for something that’s not our atomic weight so we not calibrated appropriately so what we need to go through and do is say that they aren’t in there in equal amounts try to do that what we effectively said was that fifty percent of the sample whoops fifty percent of it was that and fifty percent was the other one I well according to the information that we’re given is that true no we have to

incorporate those correct percentages into this how do we know it was fifty percent before what’s 1/2 fifty percent there’s where our 50s came from so what we need to incorporate is the actual percentage compositions for each of these four are 69 we’re looking at 0.6 0 1 1 percent for our other 10.3 989 right yes when we go through and calculate that the number we get you had at NATO right exactly 6 9.72 alright so we’ve now accounted for that appropriately so in trying to figure out your atomic mass for an individual element you have to take into consideration the percent composition how much of that is actually present within an individual sample okay a standard average as we look down before assumes that we have equal amounts for each which we can’t do hi questions about that we don’t have to divide by two the dividing by two in the first case gets us effectively our percents so if we take our i’m just going to write 6969 plus 71/2 is the same as saying that i have 0.5 percent of our 69 1 plus 0.5 percent of our 71 okay so we don’t have to incorporate that division number because that’s already involved in our percent calculation all right questions about that say white I didn’t and there’s some pseudo reasons behind that I was wondering the same thing where did this am you come from textbook just threw it in there so I was wondering why I didn’t show up our atomic mass unit is a way to represent the mass of an individual atom without having to look at the kilogram value so I don’t think I’ve got it on the slides anybody happen to remember the mass of a proton in kilograms nobody remembers I’m just going to make up a number it’s like 1.7 1 times 10 to the negative 13th kilogram right if we add it up a whole bunch of those our number is going to be awful that we would have to report on the periodic we’d have this massive exponent number okay that’s a pain to work with so what we go through and do instead is now say well an atomic mass unit is roughly 1.7 1 times 10 to the 13th kilograms so what ends up happening is we can then go through and count based on the number of protons or the number of neutrons okay so it helps simplify the mat mat so it’s an extra conversion factor which I don’t think the textbook is shown yes that number in particular no please God do not memorize that number I just made that up 24 since you’ve got it i’ll go ahead and write it up there six seven times ten to the negative 24th okay that one’s a little bit more appropriate okay so now if we took up all of our protons and added them up we could get our mass in kilograms that number is ridiculously small we could even convert it into grams it’s still going to be ridiculously small if we wanted to report that on our periodic table that’s going to be a pain to write out for every single one of the elements so what we’ve done is further converted into what’s known as am use a for atomic because we’re looking at the atom em mass you unix right so we effectively invented our own mass unit for this particular issue of looking at just an individual atom okay so that’s where that amu comes from it is convertible into kilograms if you so desired we will probably end up looking at that later in the semester and we’ll get rid of the AMU all together and convert it into something altogether much more useful again later in the semester alright some connections that we could draw on here since they mentioned it you can look at something known as heavy water right all that’s happened is that we’ve

take the same compound it’s still water still has hydrogen and oxygen in it except we’ve added neutrons and in particular we’re looking at heavy water we’ve added neutrons to the hydrogen atoms to make deuterium oxide hi so what’s happened if we look at our formula because remember deuterium is one of those common ones that we’ve used a lot instead of referring to it as hydrogen too they gave it a new symbol d so when we look at the water or the formula for heavy water it’s going to be d 20 because there’s two deuterium atoms per oxygen to generate our water it’s called heavy water because it’s got a heavier mats alright so it does change some of the properties of water they do use it apparently a nuclear reactors slow down neutrons of being released during the fission process so any questions on that there’s kind of a neat neat application to this okay so now we’re going to do is jump to chapter five and that because is because the next section in chapter four is looking at waves and light and particles and starts get all kind of loopy weird though thankfully we don’t have to go into a lot of the mathematics which you could look as a plus or minus in that case because you don’t get the explanations on where these things are coming from you just get told what they are so chapter five what we’re going to do is look at the periodic table now we have some idea of what we have as far as elements we now want to try and organize those elements into some fashion that’s already been done with for us in the periodic table but when we go back in time that wasn’t already built for us okay so there’s some history and I’m going to apologize in this case i have not had time to make my own slides so what I’ve done is cut and paste the text book lecture slides around kind of condensed them and organized it a little bit better but as far as at least the history goes pretty much just what the textbook is telling you I so 1829 ah that guy with a d3wd went through and observed that elements had different repeating patterns at that point in time we didn’t have a lot of elements to look at probably only had 20 so when he went through and started to compare what he knew about the different elements that they did have he started to notice some patterns within it hi and those patterns he saw happening in groups of three so he started to classify the elements that they had as far in triads if we take a look at our final periodic table be seen in groups of three nope so not a bad theory but wrong so we try again 1865 ah this will be fun jar Newlands this death suggested the elements be grouped according to sevens according to their atomic maps interesting interestingly enough no one believed him but he actually had at that point in time but probably one of the most accurate and it’s actually something that’s really really close to what we have now called it the law of octaves so I don’t know why they referred as groups of seven there’s many groups of eight what you were saying is every eight element repeats I so some of the properties start to cycle over so as we move across the periodic table and we could see hydrogen to helium we can see those properties being different if we then do lithium and compared with in that row of our periodic table the properties are slightly different but what he did notice is that when you get down to sodium the properties of sodium were very similar to those of lithium but not so similar to all the other elements that’s what were what they were trying to do is look at tables of physical properties okay densities boiling points melting points solubilities and looking at those in trying to group elements in the periodic table according to those properties okay what made it more difficult they didn’t have all of the elements right but some of their patterns that they picked up allow them to be able to predict new elements say hey there should be an element here because I know what’s above it I know what’s underneath it okay so there has to be some intermediary element that we haven’t yet discovered so it was kind of neat as far as discovering new elements and trying to theorize our new ones as well yes as far as the periodic table goes no the

one name that I do highly recommend you memorize will be Mendeleev because he’s considered the father of the periodic table okay so his name is important the first two guys I will not test you on that particular because i can’t say their names if I can’t say their names it’s probably a good estimate that I won’t test you on it hi but that brings up an interesting point about the history that we talked about on Thursday ok we did mention a couple names then anybody remember those names Dalton Thompson Milliken mentioned Curie and I’m running out of fingers Rutherford all five of those names are important names you do need to know those names right those were the ones that actually led us to our understanding of an individual atom these guys were just trying to organize the periodic table and were wrong if they’re wrong typically not a good name to memorize hi ah Mendeleev came along and went through and started to organize the elements according to their atomic maps which also turns out to be wrong but if you go through and look at our current periodic table and compare how they’re organized go they are set up via atomic number but if you go back and compare atomic mass holds pretty true hydrogen with atomic mass of one helium for bigger what about lithium bigger still beryllium still bigger so the atomic mass does translate fairly closely to the atomic number because the mass was easier to grasp hey why might it be easier to grasp did we have an idea of the number of protons and neutrons at that point we’re looking at it’s actually interesting that 1865 he came up with this oh that’s still atomic mass why do we not associate it at this point according to atomic number what an atomic number tell us protons and neutrons when did we know that we had protons 19th century there’s no way that they would be able to organize these according to their atomic mass or are sorry our atomic number because they didn’t even think there was something smaller than an atom so you can’t make that comparison for them the only thing that they really had to be able to measure would be the mass of those particles right so they’re looking at the mass not the number so he went through and organized it according to atomic mass and he kind of did the best organization he could do and he took it a step further and was able to actually predict new elements I had the big ones are labeled with the ekka and this Oh are labeled with eka in the middle C am I still drawing yeah okay we know what eka stands for he was Russian nobody knows what that means okay it means like so what he was saying is that this is eka aluminum whatever this element is is similar to aluminum whatever this element is similar to what’s above okay so that eka prefix he was just guessing he didn’t have an element to put in there so he just took a guess and said it had to be similar towards the previous helmet again a cub I have no idea what that means I did just make that up too and so that’s where he was able to predict these new elements so he went through and did it took a look at silicon and he knew that there was some element underneath it okay this is where he called it eka silicon similar to silicon and he had a list of all of those properties okay it was gray he knew that the weight he knew the density he knew the melting point right he knew how react with oxygen he just couldn’t predict or had actually discovered it yet right give it what is that eighteen years later 1716 a number less than twenty years later they end up discovering germanium where’s germanium on the periodic table directly underneath silicon he was able to predict the properties of that element

based on the other information that he knew from the other elements right he got colors he got weights right he got densities what they were doing is just predicting based on current patterns okay so it’s actually kind of neat to be able to do that oh darn I put another slide in here uh for germanium did he get the credit for discovering it probably not yeah what does so well he got credit for plenty of other things he got credit for determining the periodic table and organizing it into a fashion where you could predict it which is pretty huge if you take a look at discovery of the neutron who got credit for the discovery of the neutron Chadwick I think was his name and somewhere in the slides Rutherford was the one that predicted that it should exist he didn’t actually find it right so he’s tied in as potentially a footnote saying he provided the information that allowed for somebody else to discover it same kind of thing is happening here though in defense of Mendeleev in this case who did discover germy good call probably some German the name associated with it whose name is associated with it then to live hi so just because you discover something doesn’t mean that you necessarily get them what is it the historic popularity of it hi so there’s some kind of interesting history behind building that I would recommend you read up on it in a text book you can expect I really thought I have another slide in here I must accidentally deleted it the textbook I’m pretty sure we’ll go through and list at least in the homework a couple properties okay before and after an unknown element and you would be expected to predict the properties of the unknown element okay how would you do that well if you know the atomic mass of the one above it is 15 and the one below it is 20 what’s the one in between be somewhere in between 15 and 20 okay so use that information to kind of pick your middle ground and decide what’s going on that’s how he was able to predict the properties of germanium other things that you could see who’s the father of the current periodic table mentally okay so kind of simple approaches to this kind of material how to historical facts and and given a bunch of data can you analyze it and come up with effectively educated guesses about those new materials right after that we can start to look at some classifications within your periodic table the inert noble gases were discovered where is that in 1894 and they discovered that I think with argon if I read that somewhere why would they get called a nerd or noble gases what does a nerf mean not active inert means it doesn’t react so one of the things that’s interesting about our noble gases or the inert gases so you’re looking at the far right of your periodic table starting with helium working down in neon argon Krypton xenon and radon all of those elements okay when they were first discovered they could not get them to react with anything are the most common thing to react species with was oxygen okay they could not make a compound with those elements in oxygen it just was physically impossible because they did not react we called them inert all right we’ve since adapted down a little bit because it’s a funny word we came up with another word noble what is noble referring to it’s the uber-rich hoity-toity not going to interact with anybody at all just going to party okay the British there we go blame it on the British okay we’re looking at the noble gases in that respect they just really don’t react very well with anything okay you’ll notice that the end of that I said very well for the most part those compounds are fairly unreactive it turns out as we get them big enough okay how do they get

bigger how does any element get bigger okay neutrons changes the mass but what happens as we go from say argon to Krypton would you predict about size let’s discuss this yet but see what you can come up with why would it be bigger as we go from argon to Krypton why would Krypton be bigger there’s more protons there’s more electrons there’s more of everything in it what happens when you eat more get bigger okay same things happening with your periodic table the more protons and electrons and neutrons you put into it the bigger it gets okay what ends up happening is the larger you get the electrons on the outside of that atom start to become more reactive so if we get big enough into that xenon and krypton area we can actually force those molecules or those atoms to react with other species there are very difficult reactions or relatively difficult reactions to run we do kind of have to force it to occur all right so officially the noble gases aren’t completely inert which is why we typically don’t refer to them as a nerd anymore look at more as the noble gas classification they’re difficult to get to interact with anything else hi periodic law so now what we’re doing is starting to look at our periodic table read the properties of our elements recurring repeating pattern altima tlie what Mendeleev was looking at if we look at individual periods period on the periodic table is which direction row or column okay we’re saying it’s periodic law and the properties of the elements in an individual period have very similar chemical properties right when we talked about the reactivity of lithium we compared it to what reactivity of sodium or potassium we’re all where are those elements in a column your period is looking within an individual column all right so our periodic law is stating that the properties of elements within that column all have very similar properties how do we decide where those periods are that’s based on increasing atomic number all right when do we decide to loop back and start repeating within an individual period two approaches to that one you test it found out what it reacts the same there it goes must be there the other option is that you have to have some understanding of how an atom was built and what’s going on with increasing atomic number okay which is looking at the wave properties for life okay so we haven’t quite covered that yet alright so that’s the next sentence here looking at neils bohr niels bohr was able to really finally put the nail in the coffin and get us set up with the periodic table that we have today because he was able to predict what’s changing as we move through the periodic table and what’s accounting for those physical properties turns out if not the nucleus it’s the electrons okay how those electrons interact with other particles or other atoms is what’s determining a lot of the reactivity and the patterns that we see within the periodic table and a lot of the groupings that are technically up there so we will come back to that once we talk about Niels Bohr but that’s going to be a little ways out so there’s some other things that we can look at so I really label that wrong so apparently I misspoke about periods you guys were right or at least a few of you were right saying we’re in a horizontal row I’m not quite sure I liked how that previous sentence was phrased in so a vertical column we’re looking at a group or a family within a group or a family we get very similar chemistry right lithium will respond the same as sodium okay same as potassium so the chemistry within an individual family or group our vertical column is going to set us up with similar chemistry’s okay so we get repetitive chemistry’s along that direction when we look at a horizontal row that’s where we’re looking at our period or series the chemical properties change pretty drastically along that all right do we have any evidence or proof of that beryllium metallic are not metallic how do we determine metallic vs not

metallic we could look at physical properties or we look at our periodic table and we notice what was this bolded line going downwards a representation of the semi metals were on that line to be a semi metal you need to be transitioning between metals and nonmetals when we move across a period right what happens beryllium is a metal boron nonmetal okay that’s a gray area one so let’s push to carbon what’s carbon nonmetal nitrogen okay nonmetal what’s going on within a period what happens to the chemistry does that change yeah that changes a lot ok so it’s within the column that we get very similar chemistry across a row power within allegedly the period the chemistry changes rather drastically right it’s not what that last slide said I just missed read it oh that that’s what I misread this says periodic law is not referring to a period it’s saying that there are repeating patterns periodic in this case does not refer to a period I know that’s kind of an odd statement to make but that’s that’s the mistake that I made hi so your periods are by definition your rose your groups are your columns within a row your chemistry can change quite substantially within a column the chemistry stays virtually identical hi questions about that because I know I goofed it when we’re 40 right all right Wow can’t forget that I have like six classes give me a break okay some extra information we can add in here just to have people memorize stuff that said as far as a test question goes what I might ask is which of the following are not a family name and it might throw goats in there so these are your common names for individual families okay or groups so individual columns we take a look at Group one will notice that there is some interesting phrasing here group 12 15 16 17 18 where are those numbers coming from Group one starts with what element as an example I’ve actually lifted it up on the on the whatever that is the slides lithium did not include hydrogen for a very interesting reason which we’ll talk about later okay take a look at lithium okay Group one lithium is in which column why do we call that the first column in a last column we read left to right okay group to our alkaline earth metals start with beryllium where’s beryllium the next column what number proceed or proceeds follows one 20 interesting ok the next group the nick de Jin’s I just like to say that it’s just a fun word you should try and say it too ready 123 see it’s kind of fun in there starts with nitrogen in group 15 3 4 5 6 7 8 9 10 11 12 13 14 oh look at that 15 there’s our nitrogen what are those numbers referring to each column on the periodic table there is some slight debate over what those columns should be referred to a lot of that is just historical your textbook talks about that a little bit i think what they’ve settled on is I you pack just numbering them all the way straight across so you get 1 through 18 there are other numbering systems which if you look at the top of each of those columns you’ll see some of those numbering systems you see some Roman numerals you see some a’s some B’s pretty much all those just confusing and not really all that hopeful okay same with these numbers and even these names all right group 16 starting off with oxygen or refer to your child cogen’s it’s also fun 17 a group 17 or your halogens and we already talked about group 18 our noble gases okay so one thing is nice about column 18 you notice that we actually added some information in that name what information did we add they’re

all gases the provided some information about the phase and their reactivity because they are noble no pinky & T right okay everything else on within each of those columns you end up seeing similar chemistry one that will show up repetitive I say that right p diddly diddly all right your halogens the name for that individual column your halogens will show up again and again and again that one I will ask you to memorize you need to know what your halogens are what column that’s referring to that’s everything underneath fluorine fluorine chlorine bromine iodine astatine oh good question doesn’t translate all the way down into these guys okay what do you guys think that column apply all the way in okay so no why no right one thing you can look at for a no there’s a big gap between those two when we look at 85 117 270 look at the gap it is broken off of the periodic table the reason it’s broken off is that those two last column our rows are actually supposed to slide into the very middle of the periodic table very very rarely do you see your periodic table with those two rows slid in there why it makes it really really long stens it out a huge way so instead of having nice 18 rows you don’t get the 18 rows okay these elements because I don’t think I’ve actually listed on the slides are known as your inner transition elements guys go ahead and talk about that let’s list this a couple extra rows that we can add in here or groups group 3 to 12 or refer to as anybody know your transition metals why transition metals what’s happening as we move from our metals to its transitioning towards our non metals so there’s our transition metals in that inner table okay in me now exterior section of it not even quite sure how to number those let’s say elements at 57 271 and eighty nine to 10 357 271 typically refer to as the lanthanides which i’m probably butchering the smelling spelling on the 89 to 103 are referred to as the actinides why element 57 is known as no one memorized that land theme hence everything after it be lanthanides element 89 actinium hence actinides nice to say that wrong as a group those are known as the inner transition metals I typically don’t hear much talked about as far as those go because they tend to be radioactive and not anything that you guys can deal with in the lab okay so we kind of just leave them alone hi some periodic trends that we want to look at here there’s a couple of trends that we want to evaluate we can look at atomic radii so how big an individual element is right if we take a look at our atomic radius I really don’t like how they’ve got this phrased as we add elements or add do this we’re just going to memorize it at this point we’ll discuss it once we do get a little bit more on atomic structure we take a look at our atomic radius when we go down a column what’s happening we’re adding more protons more electrons more neutrons the mass increases which means what happens to the size gets bigger the more things you put in it the bigger it gets so when we look down a column at this stage that’s a relatively easy one to see okay we’ll see it get bigger what they’ve gone through and phrases looked at the negative right what happens to your atomic radius as you go up a group

okay it’s going to get smaller okay the tricky one that’s going to involve knowing a little bit more about atomic structure is looking at the atomic radius purse sorry within a period okay across a row what happens is we go left to right okay initially what might we predict as we go from lithium to beryllium tube or on the carbon nitrogen oxygen fluorine we would predict it to go bigger why the atomic mass is getting bigger we’re adding more protons neutrons electrons what actually happens to it it decreases right so we must be missing some information about how elements are put together it’s not just putting in a bunch of protons neutrons and electrons but it’s where do those protons neutrons and electrons go that are going to contribute to your radius all right which of those three sub upon subatomic particles do you think are going to contribute most to the radius protons neutrons or electrons tricky concept how about the protons and neutrons where do they exist in the nucleus as we add more yes we would expect the nucleus to get bigger we look at an atom okay we said if we took the nucleus of an atom and we made it the size of a marble what was the size of the atom superdome our protons and neutrons were all crammed into a marble yet the size of the atom was much much larger what’s contributing to the size of an individual atom is it the protons and neutrons no it’s the one particle that we haven’t really addressed that’s your electrons so where the electrons are located around the nucleus is what’s going to contribute to our atomic radii as we move down a column where I can’t say that yet as we move down the column where add adding in a lot more electrons as we move across a row it turns out we’re adding those electrons into effectively the same space which means we don’t increase the size if anything it actually shrinks a little bit okay and we will talk about that once we get a better understanding of what makes up our electron clouds right so we’ve got a pictoral image looking at your atomic radii I’m pretty sure that’s pretty much the end of what I wanted to talk about and we’re going to shift back to chapter four on thursday I and we’ll get a look at atomic structure