[Music] hello and welcome to this video on uh this is for OCB or the Salters course uh this is for atomic structure my name is Chris Harris and I'm from Aller tutors.com and yeah the whole point of this video is for revision purposes so we're basically just going to go through an overview of the atomic structure section of the uh elements for Life Topic in the Salter's course um now the slides that I'm using here um they are available to uh purchase they're great value for money if you just click on the link in the description box be able to get a hold of them there and but they are uh great for um your revision enhancing your revision all the revision techniques you've got you can put them on your tablet smartphone Etc uh it's just a different way and I suppose that because each bit comes in little bits um it's maybe a little bit more manageable um to use but they're there if you want them so like I say this is dedicated to OCB Salters and it matches the specification points taken from the syllabus so if you're doing the Salters course this should be perfect for you okay so we're going to start with the atom now the atom is uh is actually obviously very small uh and we have an incredibly small nucleus okay it's it's really really small um you're probably talking about um relative size some people have have ained this to if you put a garden p in the center of Wembley that is probably about the size of the nucleus uh of an atom compared to the the perimeter of uh of the stadium now that's just you know what people what we've heard from um from from some sources so um some people may correct me on that but that basically gives you the idea of the of the scale of this thing but the nucleus is very small contains protons and neutrons anyway in the middle electrons are in the shells and they orbit the nucleus um and they take up most of the space um of the atom now you need to know the relative charges and masses of these so for proton the relative charge is plus one the mass of it is one uh neutrons have no charge Neutron neutral so that's zero charge relative mass is the same as that of a proton and electrons have a negative charge that's minus one but their relative mass is 1 over 2,000 so it's not zero and they do have a mass that's just very very small remember this is the relative mass as well not the actual mass okay so in the periodic table obviously we have the mass number this is the top number this tells us the number of protons and neutrons in the nucleus um which is this top number here the atomic number or also known as the proton number uh just tells us the number of protons in the in the nucleus um and remember in atoms as well um all atoms are neutral so the number of protons equals the number of electrons in atoms obviously if it's an ion then that's going to change a little bit so that's an important note to make okay so we're going to look at the history of the atom and how it's developed because it hasn't just arrived we haven't just known about it it's actually been added to and amended over the time period so you can see here that we start in 1803 with John Dalton and he basically came with this idea he said that all atoms are spheres and he said that each element was a different sphere um very simple idea but it was a start okay uh and that was contributed by John Dalton way back in 1803 uh a good while after that actually after John Dalton came up with that JJ Thompson decided to have a go and he actually discovered the electron he added to that model uh and he said the atom wasn't solid uh and was actually made up of other particles and he came up with the plum pting model uh basically he said that most of the the uh atom was positive and you had negative electrons that floated around inside it and he called the positive bit the pudding bit and the negative electrons were like the plums in it obviously back then they used this model to try and explain it to people and they must have eaten a lot of Plum pulling back then um but um yeah that's basically why it's called that uh and very shortly afterwards uh we had Ernest ruford who came along just over 10 years later and he discovered the nucleus so um he said that the nucleus was incredibly small uh it was positively charged and he also concluded the atom was mainly empty space as well but he said it was made up of this negative cloud of electrons it was like a fuzziness around uh around the atom now he did an experiment to prove this um well his students did actually um him and his students which were guy and Marsden they basically took a lot of credit for this experiment um but he did the gold leaf experiment and what he did is he fired alpha particles at a thin bit of gold leaf most of them went through the gold leaf and that basically concluded that allowed them to conclude that most of these were empty space a small number were deflected back now an alpha particle is positively charged uh they were deflected back because they hit something that was had the same charge it was positively charged so um if they were deflected straight back it means they' hit the new nucleus which very very few of them did but some were deflected because obviously they came close to the nucleus but not exactly to it so that concluded that the nucleus was actually positive and the nucleus is incredibly small because most of them went through uh 1913 so again very very shortly after so they're coming thick and fast now Neils ball had a go with it and actually he said well Rutherford couldn't actually be right um he said about especially about the cloud bit he said uh he said the cloud would actually collapse into the positive nucleus CU obviously oppositely charged um and what he proposed was he said there were actual shells we had fixed energy shells and these energy shells had a defined amount of energy and he did an experiment to prove it just like Ernest Rutherford did so basically he fired electromagnetic radiation um and it was um absorbed by the atom the electrons in particular absorbed some of this and the electrons obv you moved from a lower energy shell to a higher one and when they move back down to the lower energy shell after they've emitted it um they give out some uh radiation or emit radiation and that was proof for um Neil's ball that actually there was shells and you had defined levels so you couldn't have this Cloud Theory so um basically this is kind of what we see today now obviously we can adapt to that and we've added extra bits onto there as well because we know we don't just have shells we now have these subshells uh and we call this the quantum model okay this is the model that we have today um and basically this allows us to explain ionization Trends which you'll which you'll see later on in the course um but we had P and D orbitals Etc and you'll see them later on this in this video um and that was evidence for obviously we've got subshells in our atom okay we need to look at something called nuclear fusion because we're looking at the atom so we need to look at what things we can do with the atom so elements have been formed through Fusion reactions okay really common in the sun okay the sun has got loads of fusion reactions happening all together when you fuse things together it means you're bringing them together you're you're forcing them together so Fusion like I say is the force together of two nuclei in particular okay and these make a heavier nuclei and if we got a heavier nuclei it means we have a new element so um this type of reaction understandably obviously needs to be done at very very high temperatures and pressure presses um you have strong repulsive forces between two nuclear remember they're both positively charged um so trying to push these things together is going to be remarkably difficult to do and obviously due to the extreme conditions that we need um these reactions are very common in the sun because the sun does have these extreme conditions um and obviously we form helium from two isotopes of hydrogen um just be prepared to write an equation down to show nuclear fusion you can see here that we've got obviously there's hydrogen and there's another hydrogen isotope um we fuse them together all we do is just add the top and bottom numbers together so it's pretty straightforward but this number here is unique to the element so whatever the proton number is will be unique to that element so that's how we know this is helium because helium is the only element with a proton number of two so look at the proton number and that will tell you what the element is okay so make sure they all balanced obviously that's pretty important okay larger Stars these are like really really big stars these can fuse nuclei to form heavier elements than helium okay so these are stars which are bigger than the Sun even these are huge Stars so for example oxygen and silicon could be fused together um and well we can fuse other atoms together to form oxygen silicon but they can fuse together as well uh these obviously uh have higher temperatures and pressures to allow this to happen because you're now trying to fuse really positively charged uh nuclei together so you're going to need really exteme extreme conditions to do that and obviously large Stars eventually what they do is they explode at their end of their life uh and we call this a supernova um which is a massive explosion of a large star of a giant star should we say and uh what it does it it sends all these bits of elements and fragments right across the universe some of these fragments are huge and some of them have actually been um uh formed to form some of the elements that we have on the Earth today um so actually we are a product of a star that exploded um um a long long time ago so yeah that's basically where these elements come from so thanks to these Suns uh and these Stars sorry that are fusing these elements elements together then we have the um materials and metals and elements that we do today okay so we're going to look at electron configuration now these electron shells are split them into four subshells we have the S subshell which has one orbital this can hold two electrons we have the P subshell it has three orbitals and can hold six electrons in total the D orbital has five uh or the D subshell sorry has five orbitals and that can hold 10 electrons remember each orbital can hold two electrons each so that's where we're getting the 10 from and the F orbital has uh the F subshell sorry has uh seven orbitals and can hold 14 electrons again each orbital can hold two electrons so you'd see like an example here so if we look at Shell number one um the subshells in Shell one is just one s and that can hold two electrons in Shell number two we now have a p orbital uh within shell two so it's 2s and 2 p so in total shell two can hold eight electrons and shell three h can hold up to 18 electrons you got 3 S 3 p and 3D and you can see here that we form 18 electrons in total so um yeah as long as you know obviously how they structured to gives you an idea of the number of electrons in each shell okay these are also known you might know these see these numbers as well instead of shell number you might hear them called principal quantum numbers um so just be aware that they could be used they could be using that term in the exam as well it's just the same as shell number okay basically the higher the shell number um the further away from the nucleus it is so shell number three is further away than Shell One um these have much much higher energy um than their other ones because they are a lot further away from the nucleus so um as long as you can relate the distance from the nucleus in terms of the shell number and energy that's the main thing so the further away you are from that nucleus in terms of the shell number then the more energy it has as well okay so let's look at some orbital shapes okay remember we looked at the um the four different um orbitals that we looked at um or the four different subshells that we looked at and then we looked at the orbitals within that subshell so now we're going to look at obviously um we're going to look at the S orbital um and um we're going to see what it looks like and how many electrons would would fit in Now You See obvious fit two electrons in there but it's a spherical in shape um it's a sphere holds two electrons and basically the electrons can move anywhere within that sphere anywhere within there okay that's what it basically means now the p orbital is a little bit more complicated we have three orbitals each one can hold two electrons so we got 2 * 3 so that's six electrons in total so they give them really kind of boring names Unfortunately they call it a p X orbital which is looks like a figure of eight as you can see um and that's the one that's lying on its side horizontally the py orbital is vertical and the pz orbital is coming out towards you it's like a 3D shape um now all these orbitals are 90° to each other um as you'll see there so they all kind of cluster together obviously you've got all three um closed together like that and this forms the P subshell we take all these three orbitals the PX p y and pz orbital that forms the p sub shell now there are three p orbitals like I say they're in the shape of dumbbells um or the figure of eight as you can see on there they can hold to electrons and basically that electron can move anywhere within that colored bit of the of the of the shell so anywhere within the blue bit the electron can be okay that's where the electron can move to um you might also and you're going to hear this um maybe a little bit later on as well um in the course where you hear about spin pairing basically is where we've got two electrons are occupying one orbital um as long as they spin in the opposite directions that's the lowest energy confirmation so you might have two electrons in this orbital here one will spin one way one will just spin the opposite way um so we just call that spin pairing as long as you got an awareness of that that's the main thing you'll see diagrams with arrows going up and down that's to show the uh the spin which way they're moving okay so you'll see them on these diagrams this diagrams I talking about so let's look at electric configuration okay so we need to know the different parts the big number in the front tells you the shell number the letter tells you the subshell that it belongs to and the little number there on the top tells you the number of electrons in that subshell so this is 1 S2 for example so let's have a look at the electric configuration for iron now what we need to do is look at the um because this is an element we're looking for this is the number of protons but the number of protons equals the number of electrons so ion will have 26 electrons in total so it has 1 S2 2 S2 and you can see here just with the arrows they're going up and down so that's showing the different spin that's what I was talking about before 2 P6 3 S2 3 P6 4 S2 3d6 so basically if you add up all of them they should add up to give 26 um but this is the electron configuration um of the elements and this is just showing the energy diagram showing uh how the electrons build so 1 s is the lowest energy remember this the one that's closest to the nucleus as you go further away from the nucleus like 3D it's higher in energy okay and this is just showing how the electrons fill and the Box represents an orbital whereas one of the levels here represents a subshell and obviously the number in front tells you the actual shell number okay so we always fill from the lowest energy upwards as you've just seen before um so that's quite important and we fill the orbital singly first then we pair them up so you notice here we've got them all singly paired we're not pairing these ones up they'll always occupy uh single orbitals first this because of electron repulsion they repel each other um I liken this a little bit to like a bus um I certainly find this where I live anyway where you where do you get on a bus uh and um Everybody sits on their own seat first if there's a spare seat they sit in it some people even put their bags next to them because they obviously don't want anybody sitting next to them but it's funny cuz people behave like that as well they sit on their own seat and then only if they have to when another person gets on the bus and all the seats are fill are full um then um you have to sit next to another person on the bus um so um it's a little bit like electrod they prefer to sit singly first and only if they have to will they actually sit next to another electron but um yeah it's it's it seems to be very similar that's what I find anyway you might you might think different okay so it's kind of the same same reason okay but don't write about bosses in the exam obviously okay so we're going to look at electric configuration of irons um now with ions all we do is you just add or move electrons from the or remove electrons from the highest energy level first okay we always remove from the highest level first so the electric configuration for calcium or C2 plus basically this loses two electrons uh and these two come from the um the 4S orbital so you can see here this is the electric configuration for calcium we lose the 4s2 uh and now we just have basically this configuration here so this is the configuration for 2+ now obviously you need to check your numbers as well um calcium is given the electric configuration uh has the sorry has the proton number of 20 has 20 electrons um to start off with we lose two electrons uh because it's ca2 plus uh so now we're left with 18 so make sure all these little numbers add up to 18 so we lose on the diagram here we lose the 4S there it goes and what we're left with is that uh configuration there so they might get you to fill in one of these energy diagrams as well okay so as for the configuration we can use noble gas symbols as well um a Shand method as you can see some of their methods are quite long um but you've got to be careful read read the exam question really carefully um and see what they'll accept always best airing on the side of caution unless they allow you to do so so let's have a look at potassium potassium is 1 S2 2 S2 2 P6 3 S2 3 P6 4 S1 okay so this is the electron configuration for potassium now you can see here this bit the first bit has the same electron configuration as argon so what we could do as a shorter version is we can just put a r in a square bracket instead so for example we can write it like that and that's just the shorthand version and this is using the noble gas symbol to symbolize that so this is basic tell is the noble gas configuration of argon plus that is the same as that but please read the question care because they might not get a Mark if you just write that they might want the full configuration okay transition metals they're a little bit different these okay so they behave differently so we've got the electric configuration for fe3+ what they do is they lose three electrons okay it's a form OB the fe3+ two from the 4S and one from the 3D okay which is a little bit strange so let's have a look here's the configuration here as you can see and um and what we're going to do is we're going to remove the uh 4S orbital first or the two from here and then only one from here so when we do electron uh transition metals we always remove from the 4S first if there are any electrons in there so let's have a look there it goes and there it goes on to 3d5 now if we look at the obviously the numbers and we add all the numbers up then they should give 23 because iron is 26 obviously minus the three and that gives 23 now what we do is we lose the 4S then from the 3D so we lose it from there and obviously that is the new configuration for ION so as long as you remove from the 4S first that's the main thing okay let's have a look at some electron blocks as well just the final thing um so the group number relates to the number of electrons in the outer shell um so for example group two elements have two electrons in the out shell group threes and group one sorry have group one electron the out shell Etc so um that's pretty important the ones on the left here that are highlighted in red these are called These are known as s block elements um basically the outermost electron sit in the S orbital that's why we call them s block uh these group here this group here in green are known as P block elements because the outermost electrons sit in the p orbital the purple Block in the middle here these are known as DB block elements and the blue light blue box here known as F block elements at the bottom there so you might not even have that um you might even use any of them ones but as long as you know that are F block okay and that's it um that's basically just a quick overview of um atomic structure for OCB Salters um please subscribe to the channel your support is much much appreciated um it's free to subscribe all these are free uh if you just click on the little subscription button the circle in the middle and you can subscribe to the channel and see um loads more videos to do with a Lev chemistry um also um just reminder that these slides here if you like the look of them um and you'd like your own copy then you can you're free to purchase them uh just click on the link in the description box there um they're really good value for money all right that's it now bye-bye