The Incredible Discovery of the LEAST Reactive Elements (The Noble Gases)

[Music] I'm holding in my hands a book that was written by a Scottish chemist called Sir William Ramsey the man who discovered the least reactive elements in the entire periodic table the noble gases this is a second edition which is particularly cool for a very specific reason that I'll explain later it was printed over 120 years ago and it's a magnificent story about the discovery of the gases in the atmosphere by the late 1800s it was well understood that air was not a single gas but that it was a mixture of gases mostly nitrogen and oxygen in March of 1893 an English scientist called John strut more commonly known as Lord rley due to his title as a baron published a paper where he described his method for determining the densities of different gases and he noted a strange anomaly after successfully measuring the density of oxygen he used a couple of different methods to obtain nitrogen in order to measure its density one method involved removing oxygen from regular air by passing dry air over hot copper here the oxygen reacts with the copper to form copper oxide leaving behind atmospheric nitrogen another method involved the combustion of ammonia which produces nitrogen he measured the densities of both of these sources of nitrogen and consistently found that the atmospheric nitrogen was slightly denser than the nitrogen prepared from ammonia or as he named it chemical nitrogen now the difference was only about half a percent but this was too big to be a result of experimental error so it was puzzling to really after a bit of thought he came up with a few possible explanations for this difference in density one there might have been some residual oxygen in the atmospheric nitrogen since oxygen is heavier than nitrogen this would increase the density of atmospheric nitrogen two the chemical nitrogen from ammonia might contain traces of hydrogen since hydrogen is lighter than n nitrogen this would decrease the density of chemical nitrogen three as well as the normal N2 molecules the atmospheric nitrogen might contain some N3 molecules as the N3 molecules are heavier than N2 molecules this would increase the density of the atmospheric nitrogen the first explanation was quickly disregarded because it would have required a relatively large amount of oxygen to cause such a difference in density the second explanation was more reasonable so he tested it by intentionally adding hydrogen to the nitrogen then passing the mixture over red hot copper oxide which oxidizes the hydrogen to water after doing so the hydrogen was once again removed but the nitrogen was the same density as it was before so the difference in density couldn't be due to the presence of any hydrogen the third explanation was also a reasonable one it was known that oxygen could be converted into ozone by passing it through an electrical discharge so he attempted to do the same to his samples of nitrogen to see if it had any effects on the densities but they remained unchanged no matter what he did the atmospheric nitrogen remained half a percent denser than the chemical nitrogen reallyy was at a loss but his paper caught the eye of the head of chemistry at University College London William Ramsey Ramsey had previously attempted to synthesize ammonia by passing nitrogen and hydrogen gas over various heated Metals although this was unsuccessful he found that red hot magnesium was a very good absorbent for nitrogen as it readily formed magnesium nitride after reading about ry's strange anomaly with atmospheric and chemical nitrogen Ramsey asked Ry for permission to run some experiments on atmospheric nitrogen to find out if any portion of it was different from the rest reallyy happily accepted and Ramsey got to work setting up a beautifully elegant experiment for 10 days he passed atmospheric nitrogen back and forth between two gas holders here labeled A and B the gas passed through tube G which contained The Red Hot magnesium to absorb the nitrogen the gas also passed through tube e which contained red hot copper to absorb any residual oxygen and red hot copper oxide to oxidize any hydrocarbons or dust to carbon dioxide and water the carbon dioxide would then be absorbed in tubes F and I which contained a mixture of soda or sodium hydroxide and lime or calcium oxide both of which are basic so they would react with the acidic carbon dioxide any water would be absorbed in tubes D and H which contained phosphorus pentoxide a powerful drying agent by the end of the 10 days most of the atmospheric nitrogen had been absorbed along with any residual gases that were known to exist at the time the apparatus was modified for a smaller volume of gas and the experiment was continued for a few more days finally after around 2 weeks ramsy was left with a tiny volume of gas which was around 1 18th of the volume of the atmospheric nitrogen that he started with by weighing this unreacted gas he found that it was around 20 times heavier than hydrogen this allowed him to calculate that this gas made up less than 1% of dry air The Next Step was to examine the emission spectrum of the gas this is when you supply energy in the form of heat or an electric current to a substance and observe the spectrum of light that it gives off by dispersing it through a prism each element displays its own characteristic colored lines we now know that these lines are caused by electron transitions within the atoms but at the time the reasons for these lines weren't clear since the electron hadn't been discovered yet Ramsey noted that the spectrum of this new gas contained groups of red and green lines which did not appear to belong to the spectrum of any known gas meanwhile while Ramsey was performing his experiments rley was himself continuing to work on the problem he was working on his own method of removing the known gases from Air he did so by repeating experiments made by Henry Cavendish over a century earlier the idea was to trap atmospheric nitrogen and oxygen in an inverted test tube over a solution of costic soda or sodium hydroxide by creating an electric Arc in the test tube the nitrogen will react with the oxygen to form various oxides of nitrogen all of which are acidic so they react with the basic sodium hydroxide solution below and are therefore removed from the test tube when Cavendish originally did this in the 1700s the volume of gas in the test tube gradually reduced until he was left with a small residue of gas that would not disappear upon sparking with oxygen Ry repeated this experiment and noted the same result but he then used a spectroscope to observe the Sparks and just like Ramsay saw a spectrum that didn't match up with any known gas in his book Ramsay says at this stage the two discoverers joined forces and letters passed almost daily between them they both scaled up their experiments and were able to isolate larger quantities of this new gas they found that it was extremely unreactive and would remain unchanged after exposure to some of the most reactive substances even in pretty extreme conditions no matter what they tried they couldn't get it to react with anything whatsoever this inspired the name for the gas argon after the Greek word for idle or lazy it has the same root word as the word Lethy next they carefully measured its density and specific heat and by doing some very elegant calculations they were able to determine that argon had a relative atomic mass of around 40 they were also able to Lish that it was monatomic meaning it floated around as individual atoms as opposed to diatomic oxygen nitrogen and hydrogen now 2 years before all of this in 1883 two polish chemists called Carol olevsky and Zigman breski had become famous for being the first people in the world to liquefy oxygen and nitrogen after the discovery of argon Ramsey sent olvi a sample of this new gas using his novel cooling technique osvi was able to freeze argon which in turn allowed him to precisely measure its melting point and boiling point these precise values gave further evidence that argon was indeed a Pure Element since a mixture would have melted and boiled over a range of temperatures accounting for all of this as well as its unique Spectrum it had been conclusively proven that argon was an entirely new element the discovery of argon in 1894 was a huge deal in the science scientific Community as it didn't seem to fit with any other element in the periodic table every other known element had properties in common with other elements but argon seemed to defy categorization entirely due to its extreme inertness over the next couple of years Ramsey continued to try and get argon to react with something anything he began a search for a substance that released argon when it reacted to give a clue as to what types of substances could bond with Argon this line of Investigation led to another amazing Discovery but you'll need a little bit of backstory before we get into it almost 30 years before the discovery of argon a French astronomer called Pierre Jansen traveled to India a total solar eclipse was predicted to occur in gur on the 18th of August 1868 and he was Keen to observe the spectrum of the sun's chromosphere he set up his equipment waited for the eclipse to occur and like clockwork the moon passed in front of the sun exactly when predicted using his spectrometer he examined the colorful solar prominences and he saw something interesting the Spectrum showed a clear line that had never been found on Earth before there seemed to be a mysterious elements that only existed within the Sun a few months later a couple of English astronomers called Norman loia and Edward Frankland observed the exact same inexplicable line when they looked at the sun's Spectrum loia suggested the name helium after the Greek word for the sun Helios it's interesting to note that the ending ium probably shouldn't have been used here as it normally only applies to metallic elements but loia being an astronomer was probably unaware of chemical conventions loia would go on to found the famous scientific journal Nature now for years this sun element wasn't thought to exist on Earth nobody could find it anywhere that all changed in 1881 an Italian physicist called Luigi Palmieri was studying the eruptions of Mount Vesuvius overlooking what was once Pompei he collected samples that he found near the edge of a volcanic Vents and when he heated them up in his lab and examined the gas that they released with a spectroscope he saw the distinct line for helium this made Palmieri the first person to detect helium on Earth although some scientists were still skeptical skipping ahead a few years to 1895 Ramsay was searching for a substance that contained argon he learned that the American chemist William Francis hillbrand had heated a rare mineral called cite and had collected a large volume of nitrogen from it by this point Ramsey had become an expert at analyzing nitrogen so he sent off for a sample of the mineral and started investigating it himself he heated it up with sulfuric acid collected the gas that was produced and used Ra's method to remove the nitrogen and oxygen hoping to be left with argon but when he looked at the Spectrum of this gas he found that it was different to argon he compared the Spectrum to the spectrum of the Sun and found that he had discovered terrestrial helium Ramsey got straight to work investigating its properties and found that it was very similar to argon like argon it was extremely unreactive and like argon it was monatomic in his book Ramsey said that it is therefore reasonable to place it in the same class of elements as argon so suddenly the completely unique element known as argon that didn't seem to fit anywhere in the periodic table had a sibling helium Ramsey said after the discovery of helium it appeared certain that other gases remained to be discovered now it was known that these inert gases could be found by heating different substances a very large number of minerals were heated in a vacuum and the gases they gave off extracted however despite all his searching Ramsey was only ever able to find more argon or helium Ramsey suspected the the atmospheric argon might contain a small quantity of an Undiscovered inert gas he set out to liquefy a large volume of argon so that he could use a technique called fractional distillation to separate out anything that was in there the idea was to very slowly raise the temperature of the liquid argon since different liquids typically boil at different temperatures if there were indeed other elements mixed in there they would boil at different temperatures to each other and one by one they could be separated there's a great article on chemistry World about Ramsey's life which describes his Fierce rivalry with James duer who is probably most famous today for his invention of the je flask also known as the vacuum flask according to the article to confirm the status of argon and helium and to isolate any further atmospheric gases ramsy needed large scale facilities for liquefying and fractionally Distilling air but Britain's leading expert in this field was his opponent JEA instead Ramsey turns to William hamson with whom JEA was also in dispute now in 1895 hamson patented an Innovative process for liquefying gases and he licensed it to brin's oxygen company which later became the industrial giant British oxygen now known as Bo hamson gave Ramsay some advice and a liter of liquid air so Ramsey and his assistant Morris Travers set off to build their own distillation apparatus a lot of it improvised from recycled equipment by this time they had around 15 L of isolated argon ready to liquefy and distill but since it had taken them months to amass that amount they wanted to use the liquid air that hamson gave them for some preliminary experiments to see if they could find anything before risking their precious argon on the 30th of May 18 1998 they very carefully increased the temperature of the liquid air and allowed most of it to boil off to see if the drgs contained any undiscovered gases after removing oxygen and nitrogen from the leftover portion they were left with a tiny volume of an inert gas the density of this sample was significantly higher than that of argon suggesting a heavier gas was mixed in there with it they then examined it spectroscopically Ramsey said while it showed the well-known argon Spectrum two brilliant lines were also visible one in the yellow and the other in the green part of the spectrum they gave this new inert gas the name Krypton from the Greek word for hidden it has the same root as words like Crypt or cryptic on discovering Krypton they now felt confident to start investigating their 15 lers of argon to see if they could find anything else a few days later they got to work upon ifying their 15 L of argon reduced to a volume of about 11 cubic cm just like with the liquid air they' very slowly increased the temperature of the liquid argon and the first portion that boiled off in other words the gas with the lowest boiling temperature was collected this time its density was found to be significantly lower than that of argon indicating that it was made up of lighter atoms what's more its Spectrum was completely unique another new element had been discovered they named this one neon from the Greek word for new it has the same root word as words like Neolithic and neoclassicism they kept at it performing countless fractionations of the portions they'd already isolated over and over again trying to separate off something new eventually they found that if the Krypton fraction was isolated and pumped away slowly it left a residue behind this residue had a density even higher than that of Krypton in indicating an even heavier atomic mass they examined the spectrum of this residue and once again it was a new element they named it Xenon from the Greek word for stranger it has the same root as words like xenophobe and Xenomorph neon Krypton and Xenon were all shown to be monatomic and extremely unreactive just like argon and helium so in a matter of days Ramsay's inner gas siblings had grown into an entire family five new elements making up a brand new group in the periodic table this really was amazing work a few years later in 1902 Ramsey was knighted in 1904 Ry won the Nobel Prize in physics and Ramsey won the Nobel Prize in chemistry both in relation to their work on the inert gases they were the first ever British recipients of these prizes now I'd like to show you why this second edition of Ramsay's book is so special in his preface to the second edition dated December 1900 so just 4 years after the publication of the first edition he says the following since the publication of the first edition atmospheric air has been found to contain other four inactive gases belonging to the same class of elements as argon these are helium discovered by myself in 1895 in certain Rare Minerals but first separated from the atmosphere in 1900 and neon Krypton and Xenon I mean just imagine that you discover a new element write a book about it and then 4 years later you're following up with a second edition which now details the discovery of four more elements it truly was an incredible achievements but the story doesn't end there a few years earlier on the 21st of December 1898 Pierre and Mari C discovered a radioactive element that was later named radium in 1900 a German physicist called Frederick Ern dor noticed that radium compounds emanate a radioactive gas that he named radium emanation after a recent discovery by the New Zealand physicist Ernest Rutherford who had found that thorium compounds also emit a radioactive gas which he called thorium emanation shortly afterwards a French chemist called Andre Lou dubian discovered actinium emanation now all of these emanations despite being radioactive were found to be extremely chemically unreactive so they naturally drew the attention of Ramsey by now he was a master at isolating gases so he performed an experiment over 2 weeks where he isolated some radium emanation from radium bromide he noted that its Spectrum had a striking resemblance in general character to the Spectra of the gases of the Argon group he suggested that this gas might belong to the same group as his recently discovered iner gases in 1909 Ramsey published a paper where he went into more detail about the properties of radium emanation when you look at the trends in properties of all the previously discovered inert gases this new gas seemed to fit perfectly as the heaviest element in the trend in a paper published in the French Academy of Sciences in 1910 Ramsey suggested the name niton from the Latin word for shining due to the gas's luminescent proper ities this name was initially accepted and Ramsey uses it throughout the fourth edition of his book however in the 192s the international Union of pure and applied chemistry who to this day standardized naming conventions in chemistry selected the name radon after radium the element where this emanation had been discovered by this time the concept of Isotopes had also been discovered and it had been determined that the thorium and actinium emanations were actually just different isotop toes of radon sadly in these early days of radioactivity nobody knew about the dangers of exposure to these substances Ramsey was one such victim after a lifetime of enormous contributions to chemistry he died on the 23rd of July 1916 from nasal cancer at the age of 63 Ramsey was a brilliant chemist whose work affects us to this day his inert gases eventually became known as the noble gases and their unique set properties have given them various applications since their Discovery for instance using an atmosphere of argon allows modern scientists to perform reactions that would otherwise be impossible in air liquid helium and neon are used as coolants for superconducting magnets and Medical Imaging Krypton is used in high performance light bulbs Xenon is used as an ion Thruster for spacecraft radon is used in radiotherapy to treat cancer patients but by perhaps the most obvious use of the noble gases is as beautiful glowing lights in glass tubes Illuminating city nights so the next time you see a neon sign just pause and take a moment to appreciate the amazing work that's gone into lighting it up leave a comment below if you'd like me to make a video about the discovery of any other elements and if you enjoyed this video I'd really appreciate you subscribing thanks for watching and I'll see you in the next one

Channel: Chemistorian

Views: 194,542

Keywords: Noble gas, Nobel gas, Helium, Argon, Krypton, Neon, Xenon, Radon

Id: loqudG71uBM

Length: 22min 25sec (1345 seconds)

Published: Sun May 26 2024