Investigating the Periodic Table with Experiments - with Peter Wothers

disappeared, it has reacted with water to form. lithium hydroxide, okay, so we form lithium hydroxide and hydrogen gas, okay, it's completely gone, well actually, it's not just lithium that does this, some of the other elements also react with water to form alkalis, potassium and sodium. Lithium is not on this list because it was not discovered when Marseille wrote this edition of the book. Let's try the next element under lithium and this is the element sodium, so I'm going to try a little bit of sodium with water, so I'm just going to take a little bit of sodium and add it.

This in the water. There it is and it's actually bubbling on the surface of the water or there's a little flash of flame. This is a remarkable substance. I mean, nothing like this had been seen before when Davy first isolated this, he thought. Is this really a metal? Metals are not lighter than water. They shouldn't vote. They do not react with water in this way. This is something that has never been seen before, but all the elements in our Group one, except hydrogen, which is a gas. Everyone reacts to water the same way now, that was a bit disappointing, we couldn't really see what was going on there.

You should try a larger piece, what do you think? Try a larger piece. Okay, okay, I think Chris's hair has a special tank designed to do this reaction safely, okay, so this is a special tank designed to do this reaction safely. I can't just a few for this one if you can back up a little this is a one you'll need to get right thanks so it's made of super strong polycarbonate there is water at the bottom of the tank and there are actually three different lids on top and this is to make sure that it's safe to do the experiment because we're going to use a bigger piece of sodium, so I have some bigger pieces here, okay, and here's my biggest piece, it's definitely bigger now I should have a little bit.

Be careful when I add this because, as I say, there are three different tapas, which are for walking, okay, okay, as we go this way, are we okay? It's always a little stressful this one, okay, okay, we were ready with this, so I need to make sure that Understand this, there are, let's say, three caps and three holes that I need to line it up. Okay, you're ready. Good, Chris. Well, now I especially like doing that experiment. I think it is very important to do so because this is one of the elements that is often used. shown in schools in schools is, um, the GCSE syllabus, the teacher tests the little bit in the water there like you saw and you can hardly see anything and then they go on to use a little bit bigger and then they say, okay, I use a bigger net and I'm telling you, I've heard so many cases where what happened is that the sodium was in the water and it exploded and then spilled burning molten sodium everywhere, which sounds funny and unless you're one of students covering themselves with burning molten sodium. and so it is really very important to show this.

Interestingly, in the descriptions of one level, you say that lithium just bubbles silently, sodium bubbles but there is no flame, potassium goes with a flame, well, as you saw, it's nonsense, we certainly have a flame there. sodium, but surprisingly, even though this reaction has been known since Davies' time in this explosion, it was thought to be exploding due to the hydrogen that is released during this reaction, but in reality it is not and the reason for this is only recently within It has been discovered in recent years what happens during the chemical reaction is sodium. Remember that the outermost electron was buzzing with our entire group.

That electron is easily lost and if an atom loses its electron it becomes positively charged and what happens here. the charge on our molten sodium is becoming more and more positive and of course we know that like charges repel each other and therefore what happens when the charge builds up too much and separates is called a Coulomb explosion Bukh or a charge explosion, that is the reason we have the explosion there, this has been studied recently so with high speed photography you can see the sodium literally separating and this has been modeled using theoretical computers to demonstrate that this is what happened there, but this is all relatively new, well, let's go to our group of two elements so that you remember that they all have two electrons in their outermost shell.

I'm not going to show you any beryllium at the top of the graph here. Because all beryllium compounds are very toxic, I can't show you any beryllium, but I can show you some of the others. In fact, let's look at the element magnesium and I have a little piece of magnesium here and This reacts with the oxygen in the air and gets a fantastic bright white light. The white smoke here is magnesium oxide. Okay, but the formula for the magnesium oxide that we're making there is good, it's one magnesium times one oxygen or they use the Mendeley system.

There are two atoms of the element, so two magnesium combined with two oxygens and magnesium are in group two. Well, try a larger piece of magnesium. Yes, exactly. I have a nice big chunk of magnesium. This is magnesia. Leave it airy, very light. it's pure magnesium so I just put this on the flame okay I'm heating the end there so while we're waiting for it to work well we saw that the lithium and sodium reacted very violently with the water without our magnesium so yeah take a little piece of the magnesium ribbon, so here is the magnesium, if I add it to a little bit of water, it sinks, in fact, it's just the metals in our group one, the lightest, so it's lithium, sodium, potassium, these are the only metals that are less dense. and water, so even all of group 2 sink, but in reality even this one does not react very quickly.

Reacts very, very, very slowly. If I heated it to a high temperature, it would react, but if I choose the element below the magnesium, this is calcium, this reacts a little more vigorously, so if I take a little piece of calcium, here's a little calcium and I add this to the water again, the calcium sinks, but we instantly get bubbles of hydrogen gas coming out here in the chemical reaction. Calcium reacts with water to form calcium hydroxide. That's the same substance that we made here, but I'm there in action with our calcium oxide with water, so we're producing calcium hydroxide, that's what makes the water very cloudy here at the moment because it doesn't actually it dissolves really well but we're also getting hydrogen gas, they're good at it, well, without my magnesium, it doesn't seem to be reacting and actually that's probably a good thing, it would be a bad day.

Yes, this thing caught fire but it's because it's too big, okay, it's too big to react and this is because at this moment it has taken away all the heat from this Bunsen that while I was heating it there and the heat has been spreading and it's been little a bit absorbed into the block here and dissipated from the block as well so actually I can still pick this up it's not hot enough but it can't get hot enough for the reaction to start and combine with oxygen okay it's too much big. Well, yeah, what we actually need is a very thin magnesium ribbon to get a nice quick reaction here, so this was too big there to react.

In fact, this was cut from an even larger piece and an ingot of magnesium that was made by pouring molten magnesium into a mold and this would actually melt before reacting with the oxygen in the air and bursting into flames there, okay, yes, it's perfectly safe to heat it up, but I still feel relieved anyway, now back to Mendeleev's

table

. for a moment and we will see that one of the true geniuses of Mendeleev was and is probably why we are celebrating the anniversary of his

table

and not the true first table, this is due to some of these gaps that he has in his Present these horizontal lines , some of them, for example, the line we see here is where he thought that maybe the trio element should go here, so underneath he put the question mark YT.

Well, YT is not the symbol we use now. just why, but he was right, the atrium should go to that space, okay, so one was a known element, but some of them were actually elements that were not known at the time and elemental. I said well he thinks there should be some elements here and he even predicted the properties of these elements and the compounds of these elements and he was right and this is what he recognized and this is probably why his system everyone paid attention to this, they thought well if you can predict these properties so well there must be something in your system and that's why we're celebrating your system today so let's take a look at one of these we have the symbol EB and this is under B we have B and then Al. and then e BL then EB this means eco boron echo was the Sanskrit meaning one, it is a space under the boron there if we ignore the aluminum okay and the EO is a space under the aluminum so this element EB was discovered shortly after and was work named after the discoverer of the element scandium Mendeleev predicted that its atomic weight was 44 turns out to be 45 but the most important thing is that he predicted the formula of the oxide of this and how it behaves, so he said that the formula should be two atoms of the element with three oxygen atoms and when scandium oxide was discovered, it was found to be two scandium atoms with three oxygen atoms in there, so all of Mendeleev's predictions were right, well, where did he scan it.

I'm in the Mendeleev system. there he actually mixed some of the elements from group 3 and with those from group 13, this is because both groups have three electrons in their outermost shell that are available to form bonds and that is why they are sometimes in his system al less grouped together, okay, but they should be in this modern way, separated like this, okay, let's look at some scandium, so I have some scandium here and it's very expensive because it's actually very rare. why Mendeleev didn't know about it because it hadn't been discovered because it's quite rare and that's why it's quite expensive, but I thought I should get some to show you because I'm sure you want to see how it burns, who would?

Yeah, he's never seen scandium burning before, so let's try it, so I've got some very finely divided scandium here and if I heat it up it should burn with a bright white flame. It was quite exciting, was it with a bright white flame? called that forms scandium oxide, a very violent reaction, but in fact it is two atoms of scandium with three atoms of oxygen, okay, let's choose one of the group three elements, so we have boron on the top and below boron we have aluminum, can we do it? Same thing with aluminum, so now I have some aluminum.

Who thinks that aluminum is going to burn very easily? Who thinks it won't burn very easily? Well, let's try it, so I have aluminum foil. Well, of course, it doesn't burst into flames. We wrap our turkeys with this when we put them in the oven. Oh, not because I'm a vegetarian, but it doesn't burn anyway and in fact part of the reason is that rust forms and the formula for rust is again two. atoms of the element with three oxygen atoms, but that's part of the reason it doesn't burn because it's actually protected by a layer of aluminum oxide that prevents it from bursting into flames, which is probably a good thing when we use it . or of course with our saucepans if we have a large aluminum saucepan it does not burn instantly and again it is because it is quite large like this but it is also protected with a thin layer of aluminum oxide but the rust forms and So this probably has quite a rust now so we can form this rust.

I'm going to try this a different way. The formula for aluminum oxide is two aluminum atoms with three oxygen atoms and I can do it, but. I need very finely divided aluminum. Remember that my big block of magnesium didn't really react if I split the Magni aluminum very finely. It should be fine, but I'm going to do this a slightly different way. Well, I have it in the pot here. aluminum powder mixed with iron oxide. Well, now the aluminum really wants to combine with oxygen. It is a very vigorous reaction when aluminum oxide is formed. So what's going to happen here?

The aluminum powder is going to steal the oxygen from the iron oxide and this. It's going to form aluminum oxide, which is the driving force of this reaction, but the other byproduct, this is fine, if the iron has had all the oxygen removed from the iron oxide, we'll be left with iron, so we should be making a little iron, this is another one. I'm just going to ask you to back off a little bit if you don't mind and kiryat, it will be the best for you, okay, then, okay, maybe just a little more. You can just come back later, that's great, that's lovely, okay, thank you, so now sticking out of this, I have a little piece of magnesium tape, so initially I'm going to like it and that will then start the reaction.

We will see a white flame and the bright white light of magnesium and some of the magnesium oxide smoke, sothe extra electrons that we have essentially don't go between the nuclei, they go or out of the regions here and this starts to separate the atoms again, okay if we go from nitrogen to oxygen, the bonds weaken we still have an extra electron per atom and again These electrons are now in regions outside the two nuclei, here they are starting to separate the atoms, we call it, we say these electrons have to go into antibonding. levels those in the middle here keep everything together these are bonding electrons we say that these here are entering antibonding levels and if we continue with Floreen they are weakening even more so they almost separate everything and then finally yes We went to the neon, well, neon has just the right amount of electrons and any bonding we had would be completely more than canceled out by these electrons at these antibonding levels, there is no bonding at all, that's why all of our noble gases exist as individual atoms. it's because we can't have bombs because we have too many electrons, we would form equal nuns, bonding and antibonding electrons, there are no net bonds, this same pattern, when your bonds become stronger and stronger and stronger and then we can, we can, we can heal.

Let's see not only as we cross the first row of the

periodic

table but also as we cross the next row, so the elements below we see again the same peak in the middle for the element below carbon, this is the element silicon that goes down again. We see the same pattern in the next row where we see germanium in group 14 with the strongest bond and then they become increasingly weaker in the individual atoms of our noble gases. In fact, surprisingly we even see the same pattern for the same reasons that we cross the line with the transition metals, this is the last one and it's quite fun now, actually, but before I show this, I'll just show you a different way.

I've seen this, so let's say we see. Same pattern here, so the bonds with potassium, sodium and lithium are all very, very weak than the really strong bonds in the middle with carbon and then individual atoms on the other end, but I can show how weak the bonds are with my Group One items, where is it? my glasses, what have I done? Oh, thank you, yes, okay, I'll put them on. I'm going to show you how weak the bonds are, so remember the graph here says how much energy it takes to separate these atoms, but what I have here.

There are a lot of potassium atoms, so this is a piece of potassium metal and what I'm going to do is just heat this piece up. Now there is no oxygen in my flask to react with the potassium, so we have completely evacuated the flask and it is empty. apart from the bit of potassium at the bottom, but I hope we can see a reaction when we just heat this up, we just heat this up. I hope it's easy enough to separate the potassium atoms so this is what I'm trying to do if I heat it up, which is pretty fun.

So this has now created a potassium mirror. Because it is quite easy to separate the atoms by simply heating this piece of metal, everything boils easily and turns into potassium gas which is now condensed in the cold flask, there is nothing for it to react with. okay, so it instantly covers the entire flask with this beautiful potassium mirror. If there was something I reacted to, I would react. In fact, if I turn on the tap and let some oxygen in, it will gradually react with some of this in MVCC is already losing its color there and is forming white potassium oxide there as it reacts with some of the oxygen in the air, so It is a beautiful experiment.

It's very easy to separate these atoms, but I say while moving down one of the last full rows of the

periodic

table, we see the same patterns, it's easy to separate the cesium atoms. I could have made cesium even more reactive and more expensive, so I could have made a good cesium. mirror and as I go along we are putting electrons in good bonding levels, we get really very strong bonds in the middle with the element W, what is W tungsten? Oh, well, yeah, very good, okay, so tungsten, actually, when I said carbon has the highest melting point. period, maybe with one exception, well this exception is tungsten and that's why tungsten used to be used in light bulb filaments because it could be heated to really high temperatures and it wouldn't melt or boil, so you would get it . red hot to emit light is not very efficient of course, because it is also very hot, it is red hot, that is why we now have much better light bulbs that are energy efficient, of course, these light emitting diodes, but the Tungsten is the highest melting point.

The maybe snow point between that in carbon is very difficult to measure, but if you keep adding electrons, they end up with weaker and weaker bonds and this is because we are essentially starting to put electrons into antibonding levels and mercury is a liquid, okay? and it is very easy to convert it into a very poisonous mercury vapor. This actually has another interesting consequence and this is with the density of these elements, so when I move from one atom to the next, remember that I am moving from one element. to the next we are always increasing the number of protons by one and can increase the number of neutrons and the number of electrons, so atoms always get heavier as we go from one to another, but without the density, so the density of an element depends on the mass of each atom L, but also on how closely and how tightly they are all packed together, so tungsten has the strongest bond here, so we actually see A slightly interesting curve with the densities, so even though the masses of the atoms are getting heavier, this shows the density of the solid, there is a slight delay, so it turns out that actually the osmium and the Iridium are the densest, there are still pretty good bonds and the atoms are getting heavier, but even though the atoms continue. they get heavier because the bonding is not as good, the density goes back down, it turns out gold au and tungsten W have about the same densities and this is actually quite heavy and I need a very strong one, maybe someone wants volunteer there, there, there. maybe your parents, if someone really strong there says I went up there, if that's good, then if you could come down to the front please, we will see how strong you are, this could be embarrassing, good night, then what do I would like you to do?

What you have to do, please, is just lift the bar, the bar closed for me with one hand without sliding with one hand without sliding oh, she's very easy, isn't she? So this, actually, oh, don't do that yet, okay, I'm incredibly light. this is solid it is solid it is actually made of magnesium this is even lighter than aluminum it is one of the first elements on the periodic table there are not many protons neutrons electrons per atom they are not particularly strong bonds they are quite large atoms it is really very very Turn this one on, we have more protons, more neutrons, more electrons, better bonds, smaller atoms, can you try to pick it up for me? so actually prove it, yeah, so you can wait for the good, you can write that, don't try it, you know, it's really very heavy, now you should, okay, you should try this for yourself later, we'll take out both bars outside.

Now, by the way, this was completely unfair of me because it was not a practice to do that, but whatever, we've made them the same size as a pretty standard gold bar, that's what a gold bar feels like because the tungsten and gold have the same densities okay and it's really quite heavy so I mean hold this if you try it later with all so it really is quite heavy that's the same thing that's what it feels like with a bar of gold, as if you couldn't escape with many. one of those, is that okay with you, but the other interesting thing is that in all the movies that you see, apart from the fact that they are clearly not gold bars because they really weigh a lot, remember that in one of the James Bond movies he has it in your pocket and it slides down, you don't, you could do it very easily, but they always put the gold bars in the wrong position in the movies, so they should be like that so you can easily pick them up with one hand.

This now God, yes, yes, we are around all of those, okay, and this way is really not a sensible way to have them, which is why they must be like this, so thank you very much for that, sir, hopefully. Well, I say tungsten and gold have pretty much the same densities and that's why some very naughty people drilled out gold bars, some gold bars and put tungsten in its place and then covered them with gold on the other end and can. I don't know because it has the same density just when you cut it, can you see?

You can't x-ray it, you can't see through it, so I'm not giving you any ideas here, but anyway, tungsten gold has the same density. Let's go without after, we'll take this outside so there won't be too much work here. Well, that brings me to the end of the conference. I hope you enjoyed this I hope you had a fantastic time. Think before we go, maybe we should look at the most abundant element in the universe, the number one element, this is hydrogen, so where are you up there? So we're going to look at the hydrogen one last time before we go, so I think Chris has to do it. to have another hydrogen balloon, that's fantastic, okay, so we have one more hydrogen balloon.

I should just say that there is no oxygen inside the balloon, okay, so it won't be a very, very, very loud pop, so you should be fine, no. You don't need to cover your ears if you don't like the current bangs, please do of course, but you'll be fine, but you should. I hope everyone leaves with a nice warm glow okay so I hope you enjoyed the conference thank you very much for coming so thank you very much really thank you