Promethium - Periodic Table of Videos

many people don't think promethium is very important including the makers of my tie you can see here praesidium neodymium and promethium is round the back promethium is element 61 between neodymium element 60 and samarium element 62 now people realized that there must be an element between those two before promethium was discovered and the way that they argued this the way that they thought that they must be an element was by looking at atomic weights relative atomic masses so this is a book from 1922 which i bought as a secondhand book when I was a schoolboy has a table of atomic numbers and atomic weights and down here you can see the table of the atomic weights now it's called relative atomic mass between most of these elements the difference in weight is somewhere between two and three units occasionally it's a bit more but most of the time it's two or three and when you come to neodymium and samarium the difference is six so the gap just seemed too big so people thought they must be an element there they went through many claims we have found element 61 which turned out to be wrong and the reason why none of them found it was because element 61 promethium is radioactive it's longest-lived isotope has a lifetime of 3.7 years the most common one is even shorter you mentioned that they deduced him there must be one between neodymium and samarium because of the gap in the in the waste yet in the masses couldn't I have done the same by looking at the valence of neodymium and samarium what those things reacted with and figured out hang on this one must have 60 electrons and this one must have 62 therefore there must be one with 61 I think that when people started doing this they didn't really know about it trongs as far as I know Mendeleev didn't believe in electrons and the other thing is that these elements not so much promethium but the other ones can have variable valence so they can make different numbers of it chlorides or oxide or oxides but it is true that one chemist did used by looking at the reaction of hydrogen that neodymium reacted with two atoms of hydrogen samarium reacted with none so that he thought there should be an element that would react with one atom of hydrogen so you see Brady you really clever it was only when the Manhattan Project the nuclear weapons project started in the United States when there was a large amount of radioactive research being done that enough radioactive isotopes were formed that people had a chance of detecting it and in fact the paper announcing the discovery of promethium not by its name but as element 61 was published just a few weeks probably only four weeks before I was born so I feel a certain resonance with this element we were born and more or less the same time still a very long time ago and so I've got the paper here and what's interesting about this paper is that it is extremely modest compared to modern papers describing discovery of a new element where they're press conferences big ceremonies you can see our video about some of these ceremonies here at the end of a paragraph it just says in this paper is reported the successful separation of these three elements the first have been achieved with Radio isotopes of neodymium and these are the four words that describe new discovery and development 61 you can't get much lower key than that the paper is by three authors Mariinsky Glendenning and Coryell who were working at the Clinton laboratories at Oak Ridge Tennessee this is a laboratory that has been involved with the birth of many elements most recently they participated in the synthesis of element 117 Tennyson which is named after Tennessee now the way that these three authors separated promethium was by of what was then a very new technique called ion exchange chromatography in which they had a column of essentially plastic beads that had acid groups on it and the elements forms positive ions which can interact with the acid to form a salt and if you have liquid flowing through the column in this case it was a solution of a salt then if you put in a mixture of metal ions at the top they are the different elements are attracted with different strengths to the beads of this solid acid and they come out at different times at the bottom it turns out that the heaviest element comes out first and they have graphs which show how these different elements come out here this is the key graph where they show the number of liters going along here and the amount of radioactivity that they measure and there are different Peaks and this is the peak for element 61 once they have isolated some solution with this element in it they can distinguish it say from neodymium because the radioactive decay has a different half-life the energy of the electrons coming out is different and so on so they knew they had something different I really like reading this paper I read this one on the tram when I was going home I got really excited by the time when the tram got to the final stuff this element has had a number of different names when people have thought they discovered it and hadn't because in the old days there wasn't a committee that looked at the evidence before an element was named so it was called or people thought they would call it a lynnium presumably after illinois fleur NT 'm after Florence in Italy cyclone iam I don't know what about and finally promethium promethium comes from the Greek legendary figure Prometheus who stole fire from the gods the naming was a reference to the discovery of nuclear weapons and in a way sort of stealing the power from the gods the promethium is formed as a product from the nuclear fission of other elements and I think it's important to realize that when say a uranium atom splits not all the uranium atoms split the same way so there are a number of different pathways and one of them fairly minor pathway leads to promethium so once people started carrying out nuclear activities on the large scale nuclear reactors then in the reaction products the fission products they accumulated significant quantities of promethium so that you could start thinking about their uses and there is one use which i think is fascinating of promethium which is fairly short-lived it was a good technology but it didn't last very long with making batteries so called nuclear batteries there are a number of applications where you want a battery to last as long as possible for example heart pacemakers when you have an Electrical unit embedded inside somebody's chest thankfully I don't have one and you want the battery in that case to last as long as possible conventional batteries even the ones in our phones really don't last very long as you probably know you charge it up every day but the idea was to make so-called nuclear batteries and the idea of the premium battery was that promethium decays by beta decay that is emitting an electron which in itself is promising for making a battery because the electrons don't go very far so it's easy to stop the electrons coming out of the battery so the idea is that you mix the promethium with a material which if the atoms are hit by an electron they give out light so-called fossil fossils used to be used on old-fashioned television screens where you had a clothing which was bombarded by electrons and light came out so you could see the picture so the idea is that you have a mixture of pre medium and the phosphor which glows light comes out and you sandwich this between two photo cells and the photo cells take the light and produce a voltage and it has one enormous advantage over conventional batteries a conventional battery like this one all the ones you have in your cars are very temperature dependent if the weather is very cold it's difficult to start your car because the battery has lower voltage the Promethean battery was much less temperature dependent so it could be cooled to very low temperatures and potentially say on the spacecraft and would still produce a very similar voltage because it was not relying on the chemical reaction but on this photoelectric effect the problem and the reason why the technology has now largely been superseded is that the half-life of the Promethean is very short so the amount of promethium in your battery decayed by half every two point something years so if you were trying to travel to a distant star the battery would have gone flat long before you got there if you want one set of facts to impress your friends you can tell them that premium hydroxide is brown premium chloride is yellow and premium nitrate is pink

Channel: Periodic Videos

Views: 575,776

Rating: 4.9608564 out of 5

Keywords: periodic, videos, chemistry, promethium

Id: HplP_MY78NQ

Length: 11min 43sec (703 seconds)

Published: Wed Apr 11 2018