 So, we have completed the portion on actinides, now we will be discussing the trans actinides and their chemical properties. The trans actinides are shown in this periodic table, they are actually part of fourth transition series and starts from the element number 104, that is ethrophodium and it goes up to element number 118. Now, some of the first few trans actinides, they are experimentally studied and as the later part of the trans actinides are also theoretically studied. Now, they have been determined by physical methods, that is by counting in the physics experiments, but for the chemistry experiments, it is not possible because of the very very short applies of some of the later part of the trans actinides. Nevertheless, the early part of the trans actinides like ethrophodium, element 104, dubnium, element 105, cyborgium, element 106, acium, element 108, these are chemically they have been studied in aqueous medium. Also, gas phase chemistry of these elements have been studied extensively. There is also gas phase chemistry report of element number 112 recently. As mentioned in this slide, these lanthanide and actinides, they are called as the inner transition series and these trans actinides, they are the part of the transition series. So, the chemistry of these trans actinides, they follow the transition elements are shown in the next slide, whether they are really D block elements. Now, you see from the electronic configuration, titanium, the Z of 22, zirconium, Z of 40, hafnium, the Z of 72, zirconium, Z of 104. They have a similar electronic configuration like they have the D2 and H2 type of configuration all of them. Only in case of the hafnium and the zirconium, they have 4F 14 and the 5F 14 that is the filled F levels are also there. Same also we can do about the plus 5 oxidation state transition elements like vanadium which is 23 Z, niobium 41 Z, tantalum 73 Z and dubnium 105 as the Z. Their electronic configurations you can see that they are similar that is D3 and H2 type of configuration is there. And finally, the plus 6 oxidation state that is chromium, the Z24 molybdenum, Z42 tungsten which Z as 74 and seborgium with Z as 106. They also have similar electronic configurations that is D5 and S1. As we will be seen later in this lecture, the second and the third transition series elements are considered as the homologs of the transactinides. For example, zirconium and hafnium are homologs of rutherfordium, niobium and tantalum are for dubnium and molybdenum and tungsten are for seborgium. Now the properties of this yearly transactinides and see that these transactinides their half-lives are mentioned here. Some of the early transactinides which have been synthesized in the last century are given here like 261 rutherfordium which has a t-half of 28 seconds. And all these transactinides are actually produced by nuclear reactions in accelerator facilities. This 261 rutherfordium is formed either by a 248 curium target with a oxygen 18 beam or 244 plutonium target with a neon-22 beam. In both cases, 5 neutrons are emitted. But for this reaction, the cross-section is significantly different. For the first reaction that is the reaction from 248 curium or 10 nanoburn as the cross-section and for the plutonium 244 as the target, the cross-section is around 4 nanoburn and also the rate of production also varies even though the product is same. But from 248 curium, the rate of production is much higher because of the higher cross-section that is 3 to 4 atoms are produced per minute. And from the second reaction that is from 244 plutonium, only one atom per minute is produced. Now coming to 262 dubnium that is element 105, it has a half-life of 34 seconds and the target required for this is 249 bercelium where an oxygen 18 beam is used which again 5 neutrons are emitted and with a 6 nanoburn cross-section you have the product around 2 atoms per minute and with a 248 curium target with a 19 fluorine as the beam you have 5 neutrons are emitted and with 1 nanoburn which is a 6 times lower cross-section and that is why the production also is less you have only 0.5 atoms per minute. For the 263 dubnium, it has a half-life of 27 seconds and it is produced from 249 bercelium target using an oxygen 18 beam with a 10 nanoburn as the cross-section which is 3 atoms per minute. Now coming to the cyborgium isotopes, there are mainly two isotopes of cyborgium one is 265 cyborgium the 7.4 second half-life for this is 248 curium target with a near 22 as the ion beam reaction is done with a 0.24 nanoburn as the cross-section and 5 atoms are produced per hour. For the 266 cyborgium which has a relatively longer half-life that is 21 seconds again the target is 248 curium and the projectile is 22 neon and 4 neutrons are emitted in this case but the cross-section is nearly 1 order magnitude lower with a production rate of 0.5 atoms per hour. Now the challenges in case of the transactinite without the production and transport this is a challenge because as I have already mentioned the cross-sections are very very low in the nanoburn with less than nanoburn for cyborgium nucleates and also what type of nuclear reaction one has to carry out and finally efficient detection as well as identification. The detection it is done by the characteristic alpha decay and the time correlated alpha of the mother to the alpha of the daughter in the decay chain. I have shown that in this diagram here where you have 263 cyborgium which is decoing to 259 rathophodium so 263 cyborgium has a half-life of only 0.9 seconds and this is decaying to 259 rathophodium with a half-life of 3 seconds which is subsequently decaying to 255 nobelium the 3.1 million as the half-life. So the alpha particles you see are from 263 cyborgium has nearly 50% alpha and 50% spontaneous fission. For 259 rathophodium you have 97% of alpha and 3% spontaneous fission and for the nobelium 255 we have 62% alpha and 38% electron capture. So ultimately when you do the counting the cyborgium as only a rathophodium must have already decayed and so necessarily you have to count your 255 nobelium and if you are able to count 255 nobelium or if you are able to detect it then you can always assume that 263 cyborgium has formed. Now the experimental challenges because the production and detection rate is very very less this is a very big challenge actually carrying out these experiments so this is called as a single atom chemistry or atom atom time chemistry when you carry out the chemical reactions then you are basically dealing with only one atom at a time and as I already mentioned they are very very short half-lives ranging from few seconds to microseconds and also there is uncertainty about what time the lipid is exactly formed but that is not known as it is a statistical process with all this it is very difficult actually carrying out these experiments and many times thousands of experiments have to be carried out continuously over a period of several days and data obtained are to be finalized after getting the results. Now the requirements in the experimental setup we need a fast transport and separation system we also need an online detection system of high efficiency as well as high resolution these challenges can be met with highly sophisticated automated instrumentation now when we are talking about the transactinides many times there is this feeling that these are called previously as super-ary elements so these super-ary elements or the transactinides as they are known they are the heavy actinides which are undergoing spontaneous fusion and their half-lives becomes very very short this we know already that these heavy actinides like Lorentzium it has very short half-life I have given this table here where this 254 Lorentzium which has a 13 second half-life and like that it goes on 255 Lorentzium 21.5 seconds half-life 256 Lorentzium with a 27 second half-life 259 Lorentzium with 6.2 seconds half-life 260 Lorentzium with 2.7 minutes half-life 261 Lorentzium with 44 minutes half-life 262 Lorentzium 3.6 hours half-life 264 Lorentzium 4.9 hours half-life 266 Lorentzium with 10 hours half-life So with the exception of 259 Lorentzio, you can see that mostly the neutral number increasing the half-life becoming higher. On this basis, the transactinides should have much, much lower half-lives because they are that heavier radionuclides. Also from the nuclear physics point of view, there was prediction that there will be a island of stability predicted on the basis of the cell model at z of around 114, that is proton number of 114 and the neutron number of 184. So this was predicted much earlier and subsequent theoretical calculations have suggested that this island of stability may be at a neutron number of around 162 and with a z value of may be around 126 or may be 120, this may give the most stable nucleates. If this is the case, then based on the neutron number, we can say that element number 104, which may be giving a very stable radionuclide. So that means the super heavy elements with the island of stability may start somewhere around even element number 104. So that is the rutherfordium can be considered as one of the super heavy elements. So it starts from rutherfordium and most of the transactinides, they can be called as the super heavy elements. Now from the nuclear physics point of view, the super heavy elements, they exist mostly because of the cell effects, that is because of the magic numbers to get the extra stability and those with a lifetime of greater than 10 to the power minus 14 second can be considered as a chemical element. That means if some radionuclides which are having lower than this as the lifetime, we need not consider them as the elements. So the stability of a nucleate mainly based on the spontaneous fission, which is taking place with the heavier actinides or the transactinides and this is given by a parameter called the facility parameter, which is defined as z square by a, where z is the charge of the radionuclide and the reflection of this proton to neutron ratio, this is also depending on the z square by a or the facility parameter. Now based on the liquid drop model, we can calculate this lifetime of this or the decay lifetime, that is the spontaneous fission of this radionuclide, the red line here what I have drawn now, this gives this calculated line from the liquid drop model and those which are falling below 10 to the power minus 14 seconds, we call them as non-existent. So that way somewhere between nobilium and rathaforium, we find this region with the x value of 0.88, so x is nothing but the facility parameter at z square by a, so with this value, we can say that those elements will be non-existent. However, this is not the case and we know that this actinides lie up to Lorentzium are there and also the transactinide elements were discovered subsequently, suggesting that this cannot be predicted based on the facility parameter and the liquid drop model. So, the experimentally determined values suggest that the cell effects are very, very important and the transactinides are same as the super, or it can be considered as same as the super heavy elements based on this. Now coming to the synthesis of the transactinides, heavy elements beyond fermion that is z equal to 100, they are done by the fusion reactions and before up to fermion, these are done by neutron capture reactions and then nuclear reactors or by the in-pile reactions. Now, there are two types of fusion reactions, one is the cold fusion where the excitation energy is relatively less that is your 10 to 15 MeV. So, in that case, we use medium to heavy projectiles that is iron 58, nickel 62, these type of projectiles are used and also the targets are like lead 208 and bismuth 209. In this case, we have relatively neutron deficient products have formed and the products have relatively short half-life. The other way of producing by fusion reaction is the hot fusion where the excitation energy is as high as 40 to 50 MeV and the target actinides are 248 curium, plutonium 244 etc. and light projectiles such as oxygen 18, neon 22, 26 magnesium etc. in this case 4 to 5 neutrons are evaporated as compared to only one neutron by the cold fusion reactions and the relatively long lead neutron isopropes have formed. The cross sections are from nanopons to picobons for this hot fusion reactions, but you have few atoms per minute for rathophodium and dogmium, but only 5 atoms per hour for 265 cb. The schematic of this cold fusion and hot fusion is given here and this is the compound nucleus formed by given reaction that is 58 iron and 208 lead, you have the fusion, you get the compound nucleus 266 potassium and it gives out one neutron and forms 265 potassium. In this case, we have 5 to 10 to power 16 projectiles on the target to produce only one atom. In case of the hot fusion, we have the curium 248 as the target and the projectile is 26 magnesium as given here, you have the fusion and you have the compound nucleus as 274 potassium and it is giving out around 4 to 5 neutrons to give either 269 or 270 potassium. In this case, we have 1 into 10 to the power 17 projectiles on the target and we are getting one atom. The experimental setup is given here where you have actually this is the reaction chamber is there where you have the beryllium packed this target is there as shown here and the oxygen 18 beam is coming this way and this is that is whole system is enclosed and the cooling is done by nitrogen gas passing through this at 0.2 milligram per centimeter square and this reaction is taking place and the recoils whatever is coming out of this nuclear reaction, they are actually transported by the helium gas rate in the presence of aerosols and this gas gel outlet which is going to the collection site where the experiments are carried out with the special experimental setups like Olga or Arka. Now for the target because the very large beam current is there so this target is going to be burnt very easily that is why the cooling of the target has to be done and also we need to have this target rotated so here one such schematic is given here where you have three banana shaped targets and this field actually is where it is mounted this gets rotated and then it gets cooled also so that at one time one target is only seeing the beam after that this target is moved and then the second target is seeing the beam and finally the third target is seeing the beam that is how it is rotated and alternatively we get this target exposed to the beam. Now the product from the radio nucleates are collected in the solution form for the solution phase experiments and in the gas form for the gas phase study. Now one important part here is the atomic time chemistry the single atom chemistry now this becomes very vague if you have only one atom because when you are carrying out the chemical reaction and we know this chemical equilibrium which is given here that is A and E reacting to give X and Z so the reactants are A and E so A atoms of A and E atoms of E they are reacting to give X atoms of X and Z atoms of Z as the product and the Gibbs free energy for this is given by this equation which is simplified to give del G 0 equal to minus RT ln K the problem is when you have a bulk quantity then it is fine but when you have only single atom it can either exist as A or as X so it can either be in the left side or it can be in the right side so the equilibrium constant in that sense has no meaning however this studies how it has to be carried out so it has been proposed that such studies can be carried out by partitioning experiments where the element which is formed it will be only in one phase that means if you have a solid liquid partition or even partition between a gas phase also depending of the type of the experiment the metal which is formed which will be either in one of these phases which are in equilibrium so which is shown here this figure shows that the reaction coordinates versus the del G values and if you see this delta G value if it is for this reaction Mx plus y which is the reactant which is the the transition state is y Mx and final product is My plus X now whether it will be depending on the Mx or My depends on this activation energy whether the forward reaction is taking place or the backward reaction is taking place I mentioned here in this equilibrium reaction now if the delta G is less than 15 kilocal then the reaction time will be less than 1 second so accordingly this if you carry out the reaction it's a very very short time that is less than 1 second then we have to find out the conditions in which the delta G value should be less than 15 kilocal please. Another important aspect is the relativistic effect which is very important for the trans actinates or the heavier elements the relative effect effect is important and it has three different types of relativistic effects are there one is called the direct relativistic effect now this direct relativistic effect is thought to apply only to the innermost k and the L cells however in case of trans actinates it applies to the outermost s and p cells as well and that is how this outermost of orbitals are also gets contracted the indirect relativistic effect this leads to the expansion of the outer d and f orbitals so far the cyborgium the level sequence of 7 and 7s and 6d are inverted I have shown here a picture actually where these energy levels are given and you can see for cyborgium there is really reversal of this 7s falling below that of the 6d levels so this is how this relativistic effects becomes important which decides the chemistry of this trans actinate now there is a third relativistic effect that is called the spin orbit splitting or the SO splitting and this is called the third relativistic effect and this SO splitting decreases with increasing number of sub cells that is it is much stronger for the inner cells than that of the outer cells so each of these are of the same order each of these means this all these three relativistic effects are of same order and grows as z square that means increasing the charge it increases this relativistic effects and this is becomes very very important for the trans actinates while seeing the chemistry of these trans actinates sometimes you find that it is not matching well with the homologs because of these relativistic effects