Isotopes
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00:00
NobeliumChemistryRadioactive decayOrigin of replicationPhysiologyFunctional groupChemistChemical elementThermoformingValence (chemistry)SpectroscopyThalliumIndiumGermaniumGalliumGas cylinderAlkaliHalogenGap junctionWerkstoffnummerEsterLactitolInsulin shock therapyErdrutschSet (abstract data type)DeathCrookes, WilliamHomogeneous (chemistry)Separator (milk)Atomic numberSurface roughnessBody weightTiermodellChemistryPosttranslational modificationShear strengthFunctional groupDesiccantCaesiumOctaneRubidiumPhantom <Medizin>Song of SongsRiver sourceScandiumSpawn (biology)IslandDiamond
09:29
NobeliumChemistryPhysiologyFunctional groupNickelElectronic cigaretteOxideChemical elementDisabilityErdrutschUraniumAtomic numberRadioactive decayBody weightHydrogenOctane ratingWine tasting descriptorsRadiumWaterThermoformingPotassiumMineralogyOreUranpecherzBiosynthesisTheoretische ChemieHeliumHuman subject researchAlkali metalSpectroscopyChemistPeriodateOrgan donationGezeitenküsteValence (chemistry)Combine harvesterPlatinmetalleMineralPhysical chemistrySchwermetallBiomolecular structureRamsay, WilliamBuffer solutionHalogenInertgasLactitolSeltenerdmineralienConnective tissueGasXENON Dark Matter Search ExperimentMetalLeft-wing politicsRadonPalladiumGap junction
18:58
NobeliumFunctional groupChemistryRiver sourceThoriumChemical elementUraniumChemical propertyErdrutschMineralWursthülleBlue cheeseValence (chemistry)AluminiumTransportISO-Komplex-HeilweiseVakuumverpackungSet (abstract data type)Multiprotein complexConstitutive equationFunctional groupAtomic numberBody weightCollectingThermoformingWaterSilencer (DNA)AtomNanoparticlePeriodateMan pageBeer bottleIce frontHuman subject researchFormaldehydeElectronic cigaretteProcess (computing)Spontaneous combustionOctane ratingTiermodellRadioactive decayColourantAlpha particleElectronChemistSaltCurie temperatureRadiumLactitolMantle (geology)ElectronegativityUranpecherzLecture/Conference
28:27
ChemistryNobeliumPhysiologyFunctional groupAtomNanoparticleTiermodellAlpha particleThoriumBeta sheetMineralMetabolic pathwayChemistChemical elementUraniumRadioactive decayValence (chemistry)Human subject researchPalladiumMedical historyRepeated sequence (DNA)WursthülleRadiumTransformation <Genetik>ExplosionAtomic numberActinideThermoformingAusgangsgesteinRacial segregationPeriodateOrigin of replicationErdrutschRadonSeparator (milk)ChemistryProcess (computing)ThalliumElectronic cigaretteMixing (process engineering)MixtureGasIngredientProtein domainHematiteIslandProteinRiver sourceInclusion (mineral)Diet foodHeliumWine tasting descriptorsMan pageChain (unit)ElectronAreaKatalaseEmission spectrumHome remedy
37:56
NobeliumFunctional groupChemistryPhysiologyRadioactive decayUranpecherzAlpha particleValence (chemistry)Pitch (resin)AtomWursthülleSpectroscopyHeliumDye penetrant inspectionAtomic numberLone pairMineralThoriumLeadChemical elementBody weightRadiumContainment buildingAgeingChemistPhase (waves)Beta sheetUraniumActinideActiniumOrangitTrace elementHuman subject researchSilicon dioxideElectronic cigarettePolymorphism (biology)Man pageHydrophobic effectThermoformingIonenbindungChemical formulaChemical propertySetzen <Verfahrenstechnik>NanoparticleNeotenyDeathSample (material)Explosion
47:25
NobeliumFunctional groupChemistryPhysiologyEssenz <Lebensmittel>Setzen <Verfahrenstechnik>FoodThermoformingMixtureElectronegativityCHARGE syndromeWursthülleSpinning (polymers)OperonUraniumMan pageChemical elementNanoparticleAlpha particleGolgi apparatusAtomValence (chemistry)ElectronPressureOctane ratingSeltenerdmineralienAtomic numberWaterAreaDensityHydrogenHuman subject researchBody weightTachyphylaxieErdrutschX-ray spectroscopyBiomolecular structureDischarge (hydrology)MineralElectronic cigaretteChemistGasIronThoriumGlassesContainment buildingBrassCopperZinc
56:54
Functional groupNobeliumChemistryPhysiologyBurnWursthülleOrigin of replicationAtomChemical elementScreening (medicine)Atomic numberMan pageGesundheitsstörungChemistRiver sourceThoriumRadioactive decaySeparator (milk)Wine tasting descriptorsIsotropyMineralSecretionUraniumBlue cheeseBloom syndromeProcess (computing)RadionuclidePhenobarbitalIsotopenmarkierungGermanic peoplesPotenz <Homöopathie>Common landPeriodateWalkingAusgangsgesteinGemstoneZirkoniumRadiumTrauma (medicine)Tool steelAreaAluminiumNeotenyInduktorHuman subject researchRadiochemistryBreed standardOperonChemistryFamotidineThermoforming
01:06:23
NobeliumNoble gasProton-pump inhibitor
Transcript: English(auto-generated)
00:12
Meine Damen und Herren. Ich erunnera mich nach herne ein Pär Deutscher Wurter.
00:22
Besamder ses Wei. Sie sind nach ein ist. Zum Weisbuhl zum Kilner. Unser Wirdige Lehrer. Ein Herr Schulze von Jena.
00:41
Het uns strengthten Gewärd. In uns re ester Stunde. Voor fünfün füsig erun. Das wir nie Sagenmusen ein Endele.
01:00
Or ein Endris. Sandern nach ein ist. Weil ein Endris mein... Ich habe ihr bier, nicht ger, nehmen sie wiek. Bringsie mir ein Enderer Art von Bier.
01:21
Das kunter Wohl ein Krieg enfangen. Wir sie etwes mehr Bier wunchen... ...derfen sie neue noch einissogen. Mein darmen Herren. Here ist ein atome.
01:42
Ein model atome. And here ist noch ein. Arbe ist ist noch ein. Wohde ist ist einen. Ein scheint esilmer. Herder, ein scheint rut.
02:02
Schon füsschen zu marken, wir mas dieser... ...wei wir kömer spelten. Sehen sie, einer het ein leichte... ...ker wann sie nicht... ...ger wirn het ein schwähre...
02:23
...wann michten. Sehen sie, einer schwüllen... ...en Enderer sind. So dieser sind nicht es sober atum. Es ist nicht länder... ...arbe, sond sondern ein Enderer spertum.
02:43
So, a bleich sie kein English... ...verstehen wissen zu schon... ...erles über Istobe. Now, my lecture is in two parts.
03:02
A chemical part... ...and a physical part... ...totally distinct in their methods. And for the physical part... ...I merely am here deputizing for the dead.
03:20
For more than a century since the rise of the modern atomic theory... ...the chemical elements were regarded as homogeneous... ...the ultimate separate constituents of matter. As propounded by Dalton... ...in the first decade of last century...
03:42
...it was based specifically upon two postulates. The first, that the atoms of the same element were of the same weight... ...and secondly, that the atoms of different elements were of different weights... ...both of which could hardly have been further from the truth.
04:05
As the word isotope was coined and invented... ...to imitate two Greek words, isos, topos, the same place... ...and the same place refers to the periodic table of the chemical elements... ...perhaps it is as well that I should begin...
04:22
...by saying something about this periodic law. In the last third of last century... ...after the atomic weights of a sufficient number of the elements... ...had been accurately determined... ...it was found that when they were arranged in order of atomic weight...
04:45
...they fell naturally into families of chemically related... ...or chemically similar elements. And the discoverer of that was Newlands, an Englishman, in 1862, I think.
05:00
And he... no short description of the periodic law... ...could be better than his own words. He said the eighth element in the series... ...is like the first, like the octave of a scale of music.
05:21
That is the simple law of the beginning... ...and still holds true with a slight modification. It gives you the idea at once... ...that if you arrange the elements in order of atomic weight... ...then you will get a number of series of elements.
05:41
At first it was derided by the chemists... ...just as isotopes, atomic disintegration and all the rest of it... ...are in my time. But it is well known... ...its first success was the prediction... ...of the existence of three new elements...
06:02
...together with the approximate atomic weights... ...that they had and their chemical character. These three, gallium in 1875... ...scandium in 1879... ...and germanium in 1887...
06:21
...were predicted by Mendelius, the Russian chemist... ...to whom the present form of the periodic table is due... ...the other great pioneer... ...being Lothar Meyer, the German chemist. Shortly before the advent of the...
06:43
...short and short of this... ...the advent of the spectroscope had... I'll have my first slide, please. The advent of the spectroscope had revealed four new elements... ...existing in nature in only minute quantity... ...scesium, rubidium, thallium and indium.
07:06
Go ahead, please. That's it. Thank you. Now, these were the elements predicted by Mendelius... ...you see it once. By arranging in serial order... ...from the chemistry and the successive...
07:23
...commons being alike, you can detect it once again. So Mendelius was able to predict these three new elements. You notice three points, please. This long gap here, now filled with the rare earth... ...only one of which I think is present.
07:40
These are so alike in their chemistry... ...that they are the nearest example we had... ...formally to what we now know with isotopes. This slide refers to somewhere around 1890. The slope of the lines...
08:01
...I think it's difficult for me to see here... ...but you'll notice the lines on the slope... ...imitating devices of William Crookes... ...that it really represents... ...not, you see, a split-up set of tables... ...but a continuous spiral well around the cylinder. And that is very important. But there's just this point about it.
08:22
It was forgotten later. It would have been helpful if we kept to it. Actually, this first family at that time was the alkalis... ...and the last family, the Stettin, were the halogens. And you have, therefore, sudden change...
08:42
...from the elements that are most unlike... ...in the whole of those at the table... ...without any intervening gap. I'm referring to 1890. I say you must forget now about the chemical characters... ...of the periodic table...
09:01
...which, before this century, was of chief importance. That merely really acted only as a method... ...as a method by which the elements were arranged... ...in a certain serial order, roughly... ...but not exactly in order of the atomic weight.
09:24
The next point I want you to notice... ...is these two isolated, outstanding elements... ...in the very end. Uranium, the last, borium, the last. Then, even then, get a great number of elements...
09:43
...before you come to this sequence... ...continuous without any gaps at all. Right through from good luck to the heavy platinum metal. That's the second point of importance. And lastly was the... I've already dealt with that, I think.
10:02
I'll have the next slide, please. Now, this comes to early in the present century. There are chief differences you notice... ...with a new, absolutely new family... ...of argon or inert gases...
10:21
...discovered in the year 1894... ...by Lord Rayleigh and Sir William Ramsay. They are... Just let these words sink in... ...without chemical character. They're absolutely inert...
10:41
...and they are the buffers... ...between the strongly electronegative... ...alkalized halogens of the extreme right... ...and the strongly electropositive... ...alkali metals of the extreme left.
11:00
Now, also, the rare earths have been mainly filled in. They actually, here, have been taken out of the table. I'm afraid I'm getting mixed with my two slides. Would you let me have the next one for a moment? Next, please. That's all right.
11:20
They seem to have got out of order. I want a writer, yes. I think we haven't seen that one, have we? Writers who are not right. Here was the new table I speak about here, the rare earths.
11:44
Now, already, the discovery of radioactivity... ...in the year 1896 has begun... ...to people this vacant space... ...between the elements. We have already shown there, even beginning of this century...
12:01
...radium, echo, radium... ...the radium emanation, now called radon... ...and mandatory palladium. Now, this gap is particularly of interest to us. You'd think there was no such thing as whatever... ...between that discovery and radioactivity two years afterwards. There was, in fact, the most intimate connection...
12:24
...for if it hadn't been for the discovery... ...of those gases in the year 1894... ...and the subsequent years... ...in the atmosphere, argon only being abundant... ...the rest being in bulk, proportions of millions... ...beginning with helium, neon...
12:42
...argon, krypton, xenon. Now, helium, exceptionally... ...was found first by Sir Norman Lockyer and the Sun... ...by the spectroscope in the year 1868... ...and then it was traced by Ramsey and Rayleigh...
13:04
...to the certain minerals. A certain mineralogist, American mineralogist, Hillebrand... ...had discovered that uraninite... ...which is the primary mineral of pitchblende...
13:23
...which is the secondary form of it... ...a almost pure oxide of uranium... ...had a gas present in considerable quantity... ...which he took to be nitrogen. Miles at Oxford told Ramsey about this... ...who at that time was engaged on trying to make argon combine...
13:42
...and they separated this piece of Hillebrand... ...and it proved to be helium. The solar element, the lightest of that table... ...and the one that Lockyer had discovered... ...in the solar chromosphere in 1868.
14:07
Now, I'll have the next slide, please. Just for completeness... No, that's not... That's number three I want, please. That's four, isn't it? So I've gone.
14:21
That's better. Now, this is just an up-to-date version... ...of the present table, got it out of order somehow... ...where the homo rella, here now complete, just one space... ...been taken completely out of periodic table... ...as a complete exception. This original idea...
14:42
...of music, tied only to the first two periods... ...as they are called. After that, large numbers of elements... ...are incorporated, shown here from there to there... ...and so on, through the table... ...which increases the number of the order. But that's actually the problem...
15:00
...or fairly modernized as it was dated in 1945... ...I think, representation of the periodic table as it is today... ...and it contains practically all the work... ...about which later I shall be speaking. Now, this surrounds... Oh, of course, it doesn't contain the article...
15:23
...of the elements which Professor Hahn has already been speaking. This is extended beyond the uranium, the last ground now... ...six places further on by purely artificial elements... ...and all the fine gaps, the broken places...
15:44
...still there have been artificially made... ...by the new methods of atomic synthesis... ...which have come in quite within the last decade. Professor Hahn has written a most interesting book... ...on this subject called The New Atoms...
16:00
...that I advise you to read. I mustn't be able to point out that already by this time... ...and before the end of the century... ...it was known that there were exceptions to this rule... ...this periodic law. No less than three pairs of elements... ...had their atomic weights wrong. They were transposed. The first was tellurium...
16:21
...127.6, the atomic weight... ...followed by iodine, 126.9, less instead of more... ...and two others, argon, followed by potassium... ...cobalt, followed by nickel. So it was well known that the periodic law... ...was not an exact law.
16:42
Another point at that time... ...that aroused a very keenest interest... ...was the very large proportion of the elements... ...that were integral in atomic weight... ...in terms not of hydrogen, the lowest atomic weight... ...which is 1.008... ...but in terms of oxygen...
17:00
...which is 16. This was far too large... ...a proportion of the whole elements... ...to be due to chance... ...and it revived a very simple... ...and at first wholly derided hypothesis... ...of Prout in the beginning of the century... ...immediately following Dalton's atomic theory.
17:23
Prout's doctor had suggested... ...that because of the integral relation... ...of hydrogen and oxygen... ...very nearly, it's about 1% different really... ...but it was integral enough in those days... ...it might be true that the whole of the elements... ...were built up of hydrogen...
17:42
...compounded of hydrogen... ...and this of course was derided... ...mathematized by the exact chemists of the day... ...but science has its tragedies... ...as well as its successes. Right up to the very beginning of this century... ...when I was a student...
18:01
...the high water mark of theoretical chemistry... ...was regarded as a more and more... ...exact determination of the atomic weights... ...under the entirely false impression... ...that they must have some profound physical meaning... ...I have the light please...
18:22
...please put the light up... ...well alright, that's all there is.
18:41
Right up to the very beginning of this century... ...it was regarded as a high water mark... ...of theoretical chemistry... ...this exact determination of the atomic weights... ...under the false impression... ...that they must have some profound theoretical interest... ...which if you could only grasp... ...would solve the whole cryptogram of the periodic law. Now, 50 years later...
19:02
...it transpires... ...that the work of those original pioneers... ...beginning with Berzelius... ...Myrrheniac stars... ...ending with E.W. Morley... ...and T.W. Richards... ...the last of the American atomic weight... ...exact atomic weight chemists... ...their life work was truly thrown away...
19:23
...as if they'd been engaged in the... ...determination of the specific gravity... ...of a collection of beer bottles... ...some of them empty... ...some of them fallen... ...some of them partly fallen... ...partly empty. And yet, paradoxically enough... ...the riddle of the periodic table cryptogram...
19:45
...is now read... ...so that any child at school can understand it... ...and indeed they ought to be taught it... ...instead of a lot of the old stuff, in my opinion. The nature of the constitution of matter... ...in spite of the certain increase in complexity...
20:02
...which has to be put up with... ...has been enormously simplified of recent years. It was the object of natural philosophy... ...from the very earliest times... ...to find out the nature of the... ...the internal constitution of matter. And within the last decade almost...
20:21
...that goal has been very largely achieved. And now to my subject... ...the strange new complexity of matter... ...which is known by the name of isotopy. It was, of course, a discovery in 1896... ...by Henri Becquerel of Radioactivity...
20:40
...which made inevitable... ...the recognition of this heterogeneity... ...new heterogeneity in matter. It was established just 50 years ago... ...almost to a month. And it's strange that such a jubilee... ...should not have been considered worthy... ...of some formal scientific recognition...
21:04
...for undoubtedly... ...it has rocked the world... ...that the two naturally radioactive elements... ...those isolated pair at the beginning... ...at the end of last century... ...standing alone at the very end of the table...
21:22
...were undergoing a process... ...of spontaneous natural transmutation. The atoms are disintegrating at excessively slow rates... ...though the actual disintegration of any atom... ...is a sudden instantaneous or explosive affair.
21:41
Light particles relatively to the mass of the whole atom... ...are expelled... ...which simulate rays. New atoms are left... ...which correspond to new elements... ...with different properties. In both cases of uranium as for thorium...
22:02
...there's a long series... ...of successive disintegrations... ...in the course of which they come into existence... ...in infinitesimal quantities for most part... ...a very large number of new chemical elements... ...of which radium is typical...
22:21
...with a limited period of life... ...before they proceed to disintegrate again... ...and turn into a new member of the disintegration series. Where's my model? I have my model on now, please. This represents a model of the series...
22:43
...I won't go into it very much in detail... ...but the different colours of the various... ...model atoms represent their chemical character... ...the different colours of the rays that are being expelled... ...there are only two, white and black...
23:02
...shows the difference in the rays. Now... ...the important point is this... ...this is a primary element, uranium or thorium... ...life, average period of life... ...lasting thousands of millions of years. This may have a period of a few hours.
23:27
Indeed... ...the white... ...balls represent the alpha particle... ...which I have to say for a moment... ...the black balls are the beta particle... ...or the ordinary electron... ...flowing at a frequency of velocity of light...
23:43
...only two varieties... ...these beta rays, as we call them... ...are shortly related... ...very rarely... ...and I don't think any case longs about... ...a quarter of a century...
24:00
...but there we come down to the next era... ...this may have a slight of a million years... ...and so on, all the way down... ...but you never know, some of the lines go so short... ...that the existence of a separate member... ...is only... ...it only implies... ...you couldn't possibly distinguish between them... ...remain in millions, tens and thousands of millions...
24:22
...of a second for the shortest lines... ...but just remember that the alpha rays... ...are generally more stable... ...the alpha rays are generally more stable... ...than the beta rays. Now this slide that has not already been had... ...number four... ...fear necessary... ...that is the slide that has rocked the world...
24:42
...that is the experiment that has rocked the world... ...if ever anything has... ...that's Becquerel's first picture... ...of a uranium radiograph... ...taken by sprinkling... ...or piling over a photographic plate... ...wrapped in black paper...
25:02
...a quantity of uranium salt... ...putting in between the salt and the film... ...an aluminium medallion... ...and leaving it in a drawer... ...in the dark for weeks. A curious phenomenon... ...1896.
25:21
But... ...followed one year... ...Rüntgen's famous discovery of the X-rays... ...known by his name... ...Rüntgen and before him... ...Krux in England and Lenard in Germany... ...and very many others... ...with the very latest electrical appliances... ...the high-tension electrical generation...
25:41
...the very best high vacuum technique... ...to remove the gas from their vacuum tubes... ...had discovered X-rays... ...but this... ...we had uranium... ...doing of itself... ...and doing more powerfully...
26:01
...the very best that at that time could be done... ...by artificial agencies. That was a real wonder of Becquerel's discovery... ...it might have remained... ...just a curious... ...almost curiosity of science...
26:22
...but as is well known... ...for the work... ...the subsequent work... ...of the Curies. It was Madame Curie... ...together with the German physicist... ...G.C. Schmidt... ...who discovered... ...the radioactivity... ...of the...
26:42
...next element in the table... ...and that is a radiograph... ...of the ordinary... ...velspark mantle... ...which has been... ...before it burnt off... ...flattened out... ...then burnt off... ...and laid upon a photographic plate... ...wrapped up in black paper... ...and left for a few weeks.
27:01
You see how the thorium... ...that's a positive from the original negative... ...thorium has imprinted... ...its picture. Now this was the result of Madame Curie's... ...very careful systematic analysis... ...of the whole of the known elements... ...of which only one at that time... ...thorium was radioactive as well as uranium.
27:22
And then as well... ...everyone knows... ...that was followed by the dramatic discovery... ...of Madame Miso Curie's... ...new... ...powerful radioactive elements... ...millions of times... ...more radioactive... ...than uranium and thorium...
27:41
...which brought the subject... ...out being a curiosity... ...to a colossus... ...striding the whole modern world... ...by Madame Curie's... ...investigation... ...of the uranium mineral... ...bitch blend. Now there's only one... ...but there's a very... ...very important...
28:01
...extremely interesting feature... ...of these amazing discoveries... ...of the well known... ...the Curie's... ...for which I have time... ...to mention and I don't think... ...it's ever been pointed out before. Can I have the light please?
28:20
I think this isn't working... ...I have to tell you... ...the light. But the success of the Curie's... ...is simply due to the fact... ...that Madame Curie is a chemist... ...not a physicist. And instead like Bickel... ...working with the... ...commercial preparations of uranium... ...after they'd been treated...
28:41
...in the factory... ...Madame Curie went to the uranium minerals... ...and it was in these minerals... ...that she discovered... ...first palladium and then radium. Now it's one of the curiosities... ...of scientific history... ...that no one thought... ...at that time... ...of repeating...
29:00
...Madame Curie's work... ...for uranium... ...with the thorium minerals. And still more curious is it... ...that when it was done... ...eight years later... ...it was by reason of an accident... ...instead of being... ...a conscious piece of research.
29:21
Now the essential feature of this... ...discovery or theory... ...of the... ...disintegration of the atom... ...as being the cause of radioactivity... ...is shown for the first change... ...of the radium atom. Now called...
29:41
...radon in short... ...imitation of argon... ...and the other gases... ...as we say in the family. It's been a customary... ...fulfillage... ...to deal with the most amazing... ...changes of matter... ...in the course of their studies. Transformations which were considered...
30:02
...magical. But I don't think any... ...discovery... ...in the old fashioned... ...molecular chemistry... ...equals its interest... ...or amazing character... ...in the first natural... ...transmutation that was made out.
30:21
You have the sudden explosion... ...of a certain proportion... ...about one two thousand... ...five hundred... ...part every year... ...of the radium atom... ...into two different men. And these two atoms... ...at a firm... ...turned out to be...
30:41
...the lightest and the heaviest... ...of Rayleigh and Ramsey... ...and Algonquic. This disintegration occurs... ...and it was proved... ...very soon afterwards... ...both by... ...Mesucuri and by ourselves... ...other than myself... ...occurs with the evolution...
31:01
...of a million times... ...as much energy... ...as in the most energetic... ...ordinary chemical change known... ...which results in the helium atom... ...in this case... ...being expelled... ...the sort of rays... ...of speed of about... ...one fifteenth to one twentieth... ...of that of light itself.
31:22
There are fourteen successive changes... ...in the main series... ...that start from radium... ...from uranium, I mean... ...and ten in that... ...which start from thorium. And in addition... ...there is a minor... ...uranium series...
31:40
...starting from the now... ...notorious... ...uranium... ...235... ...which formerly... ...before it was actually... ...disknown to exist... ...was called actino-uranium... ...as it was supposed... ...that such an isotope... ...was the parent of the... ...of the actinium series...
32:01
...which originated... ...like radium from uranium. And I have now the next slide. These series are set out... ...I'm not staying... ...on them... ...in detail here... ...where you have the uranium series...
32:20
...starting here... ...the actino-uranium... ...or uranium-235... ...starting there... ...the third series... ...starting here... ...thorium... ...broken off... ...at the argon gas... ...the family... ...the emanations... ...as they were first called... ...by Rutherford...
32:41
...and discovered them... ...and then going on... ...right through the... ...very rapid change... ...which in each case... ...is shown the nature... ...of the particle... ...that's expelled... ...the period... ...and average life... ...in seconds... ...minutes... ...hours... ...and so on... ...and beginning to the end. Further to see... ...come came to know...
33:01
...in that way... ...some 40 new elements... ...almost half as many... ...as were before known. Can I have the light, please? When the chemical character...
33:21
...of a sufficiently large number... ...of these ephemeral new elements... ...had been made out... ...then a very strange situation arose... ...to which Professor Hahn... ...all alluded in his earlier lecture. Many of them... ...proved to be... ...completely identical...
33:40
...in their chemical nature... ...with one another... ...although obviously different... ...being formed... ...from different parents... ...and giving rise... ...to different products... ...being distinguished... ...by different rays... ...that have been given out... ...different periods... ...radioactively. And some of them... ...as we learnt later...
34:02
...in the later part... ...of the disintegration series... ...became chemically identical... ...with the elements... ...red... ...bismuth... ...and thallium... ...which are next... ...to the old 1890 periodic table...
34:21
...to uranium and thorium... ...at the end of the series. Now, being chemically identical... ...once mixed... ...they defy separation... ...by chemical analysis. And it was a decided... ...novel experience for the chemist... ...to come across simple mixtures...
34:40
...which could not be resolved... ...by chemical means. They could be resolved... ...by physical means, true... ...theoretically. As it happens... ...diffusion... ...one of the methods of separating... ...gases of different atomic... ...or molecular weight... ...is one of the most difficult processes...
35:02
...to carry out... ...practically. And it wasn't until... ...the necessity arose... ...for the separation... ...of the two uraniums... ...for the production of the atomic bomb... ...that it was ever really tackled... ...technologically as a process... ...that today it remains... ...one of the most marvelously...
35:22
...marvelously difficult... ...and expensive processes... ...possible to conceive. I coined the word isotopes... ...in the periodic table... ...but nowadays...
35:41
...this could be put... ...much more sweepingly... ...by turning it round. Isotope is by no means... ...confined to the radioactive elements... ...among which it was discovered first... ...so that one can say... ...that the separate places... ...in the periodic table... ...are occupied more often than not...
36:02
...by a group of different... ...but chemically... ...identical elements... ...that are now called isotopes. Now in natural radioactivity... ...there are only two ways... ...in which the atom can disintegrate... ...why no one knows.
36:21
Indeed, you might say that... ...about a great deal about this new subject. The theory is... ...the theory is merely very often... ...a crude imitation of the facts... ...the conjure of putting... ...into the rabbits... ...that the experimentalists... ...had often pulled out...
36:40
...just before. In both cases... ...the individual atom disintegrating... ...emits a single radiant particle... ...that had to be assumed at first... ...but was afterwards proved. Like a bullet... ...coming from a gun at a speed...
37:01
...a considerable fraction of that of light... ...and these particles... ...the alpha, the white ones in my model... ...and the beta, the black ones... ...in the alpha change... ...what are called by Rutherford... ...the discoverer alpha particles... ...are expelled... ...in the beta change...
37:23
...electrons... ...a very penetrating radiation... ...the beta are penetrating rays... ...like the Roentgen rays... ...going through opaque matter... ...only in proportion to the amount in its way... ...being absorbed only in proportion... ...to the amount in its path...
37:40
...and from the very first... ...they were regarded, of course... ...as analogous in every respect... ...except at a much higher velocity... ...to the ordinary cathode rays... ...of the now ubiquitous vacuum tube. That was made out almost as soon...
38:01
...as the discovery of radioactivity itself. But the nature of the alpha rays... ...took far longer to establish... ...for many years... ...they were correctly thought... ...to be atoms of helium... ...as I've already indicated... ...the solar element... ...which Sir William Ramsey...
38:20
...and I proved in... ...1903... ...was continually being produced... ...by the element radium... ...the very first case... ...of a natural transmutation... ...established by ordinary... ...physical and chemical methods... ...but it wasn't until about...
38:44
...1911, I think... ...seven or eight years after... ...their first recognition... ...that Rutherford succeeded... ...in proving in the spectroscope... ...that the alpha rays... ...were a veritable helium atom. Now, although they are... ...not the most important...
39:01
...and energetic of the two types... ...they are very, very... ...feebly penetrating. ...the remaining quantity... ...of any other substance. But it's a miracle... ...that one atom... ...can penetrate another.
39:21
That is something new... ...if you like. Here we have the... ...second lightest known atom... ...passing clean through... ...all the atoms... ...hundreds of thousands of atoms... ...of the guest... ...in which it passes. And that... ...was pointed out...
39:40
...as early as about 1904... ...by Sir William Bragg in Adelaide... ...a lone worker right away... ...from all culture... ...all research. A man, by the way... ...who had gone out to Australia... ...not as a physicist... ...but as a mathematician... ...who had trained himself... ...in experimental methods... ...entirely alone, isolated.
40:01
He had the most wonderful... ...discovery... ...of this... ...passage of the... ...alpha rays clean through... ...the atoms of matter... ...almost as if they were not there. And that's the case, if you like... ...of two particles... ...occupying the same place... ...at the same time.
40:22
And it was upon that... ...upon that property... ...that Rutherford... ...in 1911... ...to 1913... ...founded his celebrated... ...nuclear theory... ...of atomic structure. Now, it was this... ...the discovery... ...absolutely simultaneously...
40:43
...1911... ...to 1913... ...of what is now known... ...as the displacement law... ...of radioactive change... ...that cleared up this whole subject... ...like a flash. It was established... ...that when the alpha particle... ...is expelled from the atom...
41:02
...the chemical character... ...of the substance changes... ...in a way to indicate... ...that it has moved... ...in the periodic table... ...two places nearer the start. When the beta particle... ...is expelled... ...the change of chemical character...
41:21
...is one place... ...in the opposite direction. I have my next slide... ...please. This is the displacement law... ...of radioactive change... ...and it was... ...appeared in the year... ...1913 when it was discovered. It was first discovered... ...from the alpha particle... ...because it was very much longer...
41:40
...than the beta part... ...of beta rays... ...where the... ...most of the beta rays... ...are too short-lived... ...to be chemically... ...long ago... ...when I got hold of the... ...alpha rule...
42:02
...of how an alpha ray... ...is expelled. I take this as a thorium... ...the beginning of a thorium series... ...it jumps... ...two places... ...from the thorium phase... ...to the radial phase. That's a thorium... ...thorium one. Then it's...
42:20
...one, two. And then... ...and then... ...alpha, beta, beta... ...sequenced in any order... ...is very common... ...in the radioactive disintegration. The third comes about, you see...
42:41
...as a matter of frequency... ...that the great grandchild... ...of an element... ...is identical... ...to its failure. Doesn't matter the order... ...alpha, beta, beta... ...is the same phase... ...of the periodic table... ...and is absolutely chemically identical...
43:02
...although... ...four units less... ...in atomic mass... ...the weight of the alpha particle... ...that it's been expelled. It wasn't until the latter part of the century... ...that it was established, of course... ...that this actinium series... ...drives in separate isotopes of uranium... ...and runs back...
43:20
...that I haven't time to deal with. Indeed, that's a rather interesting point... ...that the actinium... ...the uranium-235... ...was only discovered... ...after all the rest of the work... ...had been made out. It was... ...foreshadowed...
43:40
...by... ...what was the man's name... ...who went up into the staphosphere... ...in a balloon... ...like Picard... ...a Swiss investigator... ...a Swiss physicist... ...who went to Belgium... ...with uranium to indicate... ...that it was a probable variant... ...of the whole actinium series...
44:01
...which you see there. We might take that just simply. There is the actinium beta... ...alpha, alpha, alpha... ...beta, alpha, beta... ...and the interesting point about this... ...was that it revealed... ...half a dozen new things... ...and one of the most important was this... ...that in every case...
44:21
...that's the end of the series... ...and... ...there is a rate of lead... ...207.2... ...whereas a calculated atomic weight... ...of lead... ...from this one, thorium... ...is 208... ...I think...
44:41
...I can hardly see... ...here... ...this is the lead 208... ...this is the lead 207... ...yes, that's right... ...the atomic weight of the lead... ...from the uranium series is 206... ...or 208... ...and the common lead is 207...
45:01
...raising the possibility... ...you see... ...of ascertaining... ...proving definitely... ...this theory of isotopy... ...because... ...one has only got to go... ...to minerals... ...which contain... ...no thorium... ...contain uranium only...
45:21
...and separate the lead from them... ...provided of course... ...originally in the mineral... ...and that had become at that time... ...a perfectly well understood technique... ...because it is a method... ...that enables the geologist... ...to determine the age of the sample... ...the age of the earth... ...and the amount of lead... ...the ratio of the lead to the uranium...
45:42
...whereas at that time... ...the geologists were against even... ...the idea that thorium... ...produced lead too... ...so they're wrong... ...I had the good fortune... ...of a new mineral called Thorite... ...the silicate...
46:01
...which was the purest... ...thorium mineral... ...at that time known... ...but it's not possible to get... ...a mineral like... ...Madam Curie's pitch blend... ...urananite... ...which contains no thorium to speak of... ...only the merest trace... ...but this particular specimen... ...of thorium mineral...
46:21
...contains only a very small proportion... ...of uranium... ...which I published most carefully... ...working up about 30 kilograms of it... ...chemically for the lead... ...I was able to separate in quantity... ...in the year 1960... ...thorium lead... ...over 208 thorium lead...
46:40
...whereas T.W. Richards... ...I've already mentioned... ...the United States atomic weight chemist... ...at that time... ...had similarly tackled... ...pure uranium minerals... ...and determined the age of those... ...which the geologists... ...for him as being suitable... ...in mud containing lead originally...
47:01
...and had found the atomic weight... ...to be 206... ...and... ...as to be expected... ...because even at that time... ...it was expected... ...that the specific gravity... ...of these atoms... ...would be proportional... ...to the atomic weight... ...the external part of the atom...
47:22
...being the same... ...only the internal part different... ...the specific gravity... ...of these two... ...totally distinct... ...isotopes of lead... ...separated respectively... ...from thorium and uranium minerals... ...were in agreement... ...with their atomic weights... ...and that's the only case...
47:42
...where it's possible... ...to test this theory of isotopy... ...with the ordinary elements... ...save the one case... ...of the atomic bomb... ...whereafter spending... ...they did succeed... ...in separating enough... ...of the uranium-235...
48:02
...by diffusion and other methods... ...from the major isotope... ...99.3%... ...238... ...and... ...as to be expected... ...because even at that time... ...it was expected... ...that the specific gravity... ...of these atoms...
48:21
...would be proportional... ...to the atomic weight... ...and only the internal part different... ...we established... ...the specific gravity... ...of these two... ...totally distinct... ...isotopes of lead... ...separated respectively... ...from thorium and uranium minerals...
48:40
...were in agreement... ...with their atomic weights... ...and that's the only case... ...where it's possible... ...to test this theory... ...of isotopy... ...with the ordinary elements... ...in place of the atomic bomb... ...whereafter spending... ...5,000 millions on it...
49:02
...they did succeed... ...in separating enough... ...of the uranium-235... ...by diffusion and other methods... ...from the major isotope... ...99.3%... ...238... ...which Phil Hahn has told you... ...just enough for three atomic bombs... ...which exploded respectively...
49:22
...at the end of the war... ...on their testing grounds... ...in New Mexico... ...and on to two Japanese cities... ...it is the absolutely most difficult... ...technological feat... ...that's ever been accomplished by man...
49:41
...it dates to the rare earth... ...it took years, it took lifetimes... ...of many chemists... ...to separate the rare earth from one another... ...each diverting themselves to one or two of them... ...but this... ...is heroic in comparison... ...and it certainly could not have been done... ...I'm quite certain... ...in any other country...
50:01
...but the United States of America... ...under the pressure of war... ...now since the loss... ...of the single... ...negative electron... ...that is the beta particle... ...sends the atom... ...in the periodic table... ...one place, one way...
50:22
...whereas the loss of the doubly... ...positively charged alpha particle... ...sends it two places... ...in the other way... ...and it was obvious to the merest... ...tyro that the places... ...in the periodic table... ...represented the internal... ...atomic charge... ...and nothing else...
50:41
...the loss of a negative... ...was the opposite... ...the loss of two negatives... ...the exact opposite of the loss... ...of one positive alpha particle... ...and so it came about, you see... ...with the cryptogram... ...the large extent was red... ...could you give me back...
51:00
...bitter Gaben-Zemir-Zeruk... ...build a dry, bitter... ...thank you. I should have pointed out the chief... ...I should have pointed out the chief change... ...that's come over this modern periodic table... ...compared with all the ones... ...that were produced before them... ...subject to the elements... ...that were gradually discovered...
51:20
...in the vacant space of school years... ...every place here is numbered... ...turning outside the regular sequence... ...in all of them... ...2, 3, 4, 5... ...and uranium at the end... ...I mean 92. Now... ...that represented nothing more or less...
51:41
...on Rutherford's... ...nuclear theory... ...than the integral value... ...of the positive charge... ...on the atom's nucleus... ...and the periodic table... ...represents nothing but the orderly... ...progressive serial increase... ...from... ...by unit of time... ...on this nuclear charge...
52:02
...the outside of the atom... ...on this theory... ...is... ...made up... ...of the... ...neutralizing electrons... ...negative electrons... ...equal in number... ...individual single electrons...
52:21
...individual single electrons... ...equal in number... ...that is always now called the atomic number... ...we found that... ...originally only for the limited... ...range at the end of the periodic table... ...from uranium to thallium... ...the last place was actually entered in that chart... ...that I showed you...
52:40
...but almost immediately... ...the Bohr-Rotherford... ...nuclear theory... ...predicted... ...oh no, I'm afraid I'm wrong... ...it wasn't the Bohr-Rotherford theory... ...it was something... ...it was a... ...the rise of x-ray spectroscopy... ...enabled the...
53:02
...positive nuclear charge of the elements... ...to be actually measured... ...even before... ...it was Briggs... ...the Briggs father and son... ...who developed it in this country... ...from the work of Lauer Friedrich... ...and Nipping in Austria... ...even before that... ...Barclay... ...one of the Liverpool chemist...
53:25
...the first class of the secondary rays... ...that were produced... ...when you bombard the various elements... ...through the periodic table... ...with high speed... ...rink and rays... ...and this in the hands of Moseley... ...led to his being able... ...definitely to call the role...
53:40
...of the atoms... ...to say whether or not... ...all were known... ...or whether any vacant places remained... ...to the next slide now... ...which I think is number... ...yes... ...that's his famous... ...what's called step...
54:02
...the regular stepwise... ...change in the wavelength... ...of the wavelength... ...of the rays... ...that are produced... ...from the elements... ...and from the periodic table... ...this is Calton... ...he hadn't gotten it... ...so he dropped...
54:21
...to the next one... ...and this is titanium... ...palladium, chromium, manganese, iron... ...cobalt, nickel, copper, brass... ...brass being a mixture of copper and zinc... ...this was shown... ...in addition to the copper lines... ...you see here the glass... ...you could tell... ...anybody could tell... ...that there was a gap... ...between that and this...
54:41
...and then... ...that's the first picture he got... ...the X-rays are relatively... ...to the ordinary optical spectra... ...and we glide... ...but of course that isn't... ...when you get up to... ...higher intensities... ...that isn't true of the others...
55:00
...and in this way... ...mostly we're able to show... ...the periodic table contained... ...ninety-two places... ...from hydrogen... ...to uranium... ...and now I'm beginning... ...to get into my second part... ...of the subject... ...the physical part...
55:22
...the way of examining... ...an element to see... ...whether it contained isotopes or not... ...homogeneous... ...or a mixture... ...of different isotopes... ...and that was a... ...purely physical application... ...of the method by which... ...JJ Thompson in 1896... ...had first evaluated the mass...
55:42
...the charge... ...the velocity of the electron... ...a negative electron... ...in 1896... ...to evaluate the charge... ...of the positive ions... ...in the electric discharge... ...of gases at very low pressure... ...which are called positive rays...
56:01
...and these positive rays... ...which are called anode rays... ...and discovered by Goldstein... ...had been examined... ...as early as 1900 about... ...by a German physicist... ...Ville Wien I think... ...who had shown... ...that their mass... ...is never less...
56:22
...that was the essence of it... ...the importance of isotopes... ...to modern knowledge... ...the answer will no doubt differ... ...according as to whether... ...you're a philosopher... ...or a practical term of mind... ...but surely isotopes provided... ...have provided both types...
56:40
...with food for thought... ...to the chemist... ...with anything of the soul of a poet... ...if there are any such... ...few discoveries can rival... ...in philosophic interest... ...the sewage of Keats... ...swam into our kin... ...we've been honored by the presence... ...and having listened to...
57:00
...Dr. Hahn... ...and I've already alluded... ...to the curious circumstance... ...that no one thought... ...of repeating Madame Curie's... ...epoch-making work... ...for uranium minerals... ...for thorium minerals... ...and it happens... ...the very first piece of original work...
57:20
...that Professor Hahn did... ...which is now... ...our greatest living master... ...in radio-chemistry... ...appeared at first... ...to involve... ...what is now known... ...to be a completely impossible lout... ...the separation of two isotopes... ...thorium and radio-thorium...
57:42
...by simple chemical means... ...as a research student... ...with Sir William Ramsay... ...he had the good fortune... ...that he told you... ...to discover a new member... ...this is what he discovered... ...radio-thorium... ...so, he went working out...
58:01
...a mineral... ...which was not known... ...to contain thorium... ...by a simple mistake... ...in the standard German... ...textbook of analysis... ...for Zenius... ...when the analysis had recorded that... ...the new mineral from... ...Sildan... ...called Thorium Knight... ...which is not to be confused...
58:25
...with Thorium... ...had been imported into England... ...and discovered by the Gemmers... ...in Ceylon... ...in their search for jewels... ...imported into Britain... ...by the Eton College science master... ...named Porter... ...sent to... ...Ramsey's laboratory for analysis... ...and had been returned...
58:41
...as mainly Zirconium... ...through an error... ...in Fresenius's analysis... ...and had then gone... ...to Madame Curie's... ...pioneering work... ...on uranium minerals... ...with a different mineral... ...and to get practice in...
59:01
...separating the radium... ...as it turned out... ...of course... ...Harn... ...was given this... ...thing nobody was consciously... ...had consciously thought of... ...of repeating Madame Curie's work... ...for the thorium minerals... ...and the similar results...
59:25
...in radio thorium... ...a body of considerable period... ...life as two or three years... ...alpha-rare... ...which produces beta rays... ...in the course of time... ...as it disintegrates... ...all the other chemists... ...radio chemists in the world... ...tried to do the same thing... ...and failed absolutely...
59:41
...if they could have separated... ...radio thorium, you see... ...from the ordinary... ...commercial thorium source... ...it turned impossible... ...but the explanation was given...
01:00:00
Another curious historical point, as early as 1907 by two American chemists, McCoy and Ross, who after trying in vain every known method for purifying thorium in the attempt to separate the radiothorium that they knew from its radioactivity was there, they had the originality and the courage boldly to state what is the central doctrine
01:00:25
of isotropy. As early as 1907, radiothorium and thorium were, in their opinion, non-separable by chemical means. So how did our magician han, Amir Tyro, at that time do it? In the
01:00:40
meantime, as he told you, he'd crossed the Atlantic, working with Rutherford in Montreal, and come across mesothorium, you see, a new member in the thorium disintegration series. In addition to the radiothorium, down we go, two feet of radiothorium, one
01:01:00
radiothorium, one bit of radiothorium. These are very short, this one's very short-lived one. That one has lightened to years, considerably longer, however, than the radiothorium. That's nine of them. Now, what magician han had done, if he was to separate his thorium from the, with the radiothorium, and he discovered the radiothorium, which
01:01:25
was not what he separated from the mineral, which is something acceptable, but which is fresh radiothorium, which grows, and it will affect the operation. The coroner Ross correctly pointed out that it was a case of showing how what an utterly
01:01:45
unanticipated fact really was discovered, inevitably as it would have been sooner or later, by the fact that the atom is disintegrating. What han had done was to separate mesothorium and thoriumite without discovering it. It gives no rays, to speak of, and this in
01:02:04
the course of time had quickly grown a fresh crop of radiothorium, is what han had discovered. He had in fact achieved the easy chemical separations of mesothorium from thorium and of radiothorium from mesothorium. The original radiothorium in the mineral
01:02:20
remained, and as it now is completely non-separable from the main constituent. It's quite any more elegant revelation of a tremendous secret so long and jealously guarded by nature be conceived. By their fruits ye shall know them. It's true not only of trees as it is of men, but of all unlikely things of the elements and of the atoms. What han and
01:02:45
ramsey working with thoriumite were doing, like gardeners trying to separate red tulips from blue after they'd bloomed. The job doesn't require a gardener at all, as anybody who's doing it is not colorblind. What the other chemists were doing, who were trying to
01:03:03
separate it from thorium, was to separate these before they had bloomed, and that no gardener could possibly do. It's very easy to underrate, looking back, the difficulties that attend even the smallest forward step in discovery, that the difficulties of McCoy
01:03:21
and Roth, which they successfully surmounted in 1907, were so great that I think it deserves recognition. It looks so simple after the discovery of the displacement law, but remember that at that time before that, it was not even known that the product of a radioactive
01:03:42
change is, must necessarily be, different chemically from its parent. Who are, if as han first thought, radio thorium and thorium were successive in the series, then no, couldn't radio thorium con rather, no possibility whatever have been discovered. Sometimes it is well, I think,
01:04:04
to keep in mind the things that might be, we can't discover, as to do it well upon those that we can. On the practical side, on the other hand, there can be few discoveries in this century likely to prove as great a boon to mankind as that of isotopes. I need
01:04:23
do no more than mention this, as we are honored by the presence of a pioneer in this field, as you have already heard, Professor George Hibberty, who used, quite in the early days, before isotopes, the name was coined, used them as tracer elements and later extended
01:04:40
it to biological and medical research. That's about the one and only thing about isotopes that the public have probably ever heard. But now that artificial atomic disintegration has been achieved, so that elements are built up, at will almost, as well as broken down by these new powerful instruments in America that we've heard about, it's possible
01:05:02
to make radioactive isotopes of almost all the common elements. Of course, still in completely unweighable amounts, doesn't matter, because you're not dealing with the weight, you're dealing with the radioactivity. And there are more radioactive isotopes than the four or five hundred common isotopes of ordinary elements I've already had on
01:05:20
the screen. Looking back to the distant days of my youth, before it became possible to break down and build up atoms at will, science then seems to have been in a preliminary, primitive stage, compared with where it is today. Almost one might say it was still at school. Even whatever discoveries there may be in the future, in the science of matter,
01:05:47
even though there were none, what were already known now and didn't know half a century ago will carry man far. One essential condition is that before it's too late,
01:06:01
war must be abolished from the earth. Let there be no doubt whatever about that. That is the unanimous opinion of every scientific man that had ever expressed an opinion on this burning question.