sign in sign up
<<
Home , Ernest Rutherford, Frederick Soddy, Isotopes of uranium, Margaret Todd (doctor), Otto Hahn, William Ramsay

Rediscovery of the Elements Soddy and III

Figure 2. This plaque is mounted at 11 University Gardens. The building, now known as the George James L. Marshall, Beta Eta 1971, and Service House, presently houses the Humanities Virginia R. Marshall, Beta Eta 2003, Advanced Technology and Information Institute (HATII) of the University of . Department of , University of North Texas, Denton, TX 76203-5070, tion of a known element to another known [email protected] Figure 1. The home of Sir George and Lady Beilby, element; this research was the basis of the the parents of ’s wife, Winifred, at future understanding of the .3 A Dinner Party in Glasgow, . During 11 University Gardens, Glasgow, Scotland. The In 1904, Soddy became at the a social gathering in 1913 at the home of his in- home is of Victorian architecture and was built in , where he formulated laws, Frederick Soddy (1877–1956) (Figure 1) 1884. Sir George was an industrial who the concept of isotopes. After 10 at was musing what to call a new concept. For a furnished 50 kilograms of uranyl nitrate to Soddy Glasgow, Soddy moved to the University of decade a plethora of radioelements, each with a for his experiments. This home served as a popular Aberdeen (1914–1919), where he co-discovered unique half-life, had been discovered at various meeting place for politics, science, business, and the element (“eka-”). universities throughout Europe and North leisure. In the drawing-room of this home, the had a distressing effect on Soddy; 4d America, and there was no room in the Periodic word “” was coined by Soddy at the the death of Henry Moseley elicited the fol- 3 Table to accommodate them. To solve this prob- suggestion of Dr. . lowing from Soddy, “When Moseley was killed lem, Soddy was proposing that radioelements at Gallipoli I felt enraged. Sometimes I think with different half-lives but with the same at that university, who was just beginning to that something snapped in my brain. . . . I felt chemical properties should be confined in one investigate the strange emanation from thori- that governments and politicians, or man in box in the Table. The scholarly Dr. Margaret um.4c For the next two years the two colleagues general, was not yet fitted to use science.” Todd (1859–1918), an M.D. and novelist friend established the elemental nature of thoron Soddy moved in 1919 to Oxford University, of his wife, Winifred, suggested1 such elements (-220), developed the understanding of where with a new mission he tried to establish be denoted by the Greek words “same place” radioactive half-lives, and discovered the nat- economic policy based on scientific laws. He (“iso-topos”) (Figure 2). Soddy shortly ural transmutation of the elements.4c It was retired in 1936, after a frustrating in his announced his idea of “isotopes” (December 4, actually Soddy the chemist, well versed in the life, with a “sense of failure. . . . in the field of 1913) in the prestigious journal Nature.2 history of alchemy, who first understood the .” He was at Oxford when he accept- significance of transmutation, before Ruther - ed the in 1921 for his research in The Life of Frederick Soddy.3 A native of ford the .3 radio-elements and isotopy at Glasgow, and for in East , 85 km south of In 1903, Soddy returned to and teaching us that could have “identical 5 London, Frederick Soddy was trained at the joined the research of outsides but different insides.” University of Aberystwyth (Wales) and at (1852–1916; the discoverer of the noble gases) Oxford University, graduating in 1898. After at University College, London, to study the The Discovery of the Radioelements (see three years as researcher at Oxford, Soddy decay by-products of . In Ramsay’s lab- Figure 3). Radioactivity was discovered by accepted the position of Demonstrator at oratory, Soddy established that was Antoine Henri when he observed McGill University, , . After a produced during the decay of radium, thus emitted invisible rays that fogged pho- he joined the group of Ernest furnishing the first evidence of the transmuta- tographic plates wrapped with paper or metal

68 THE HEXAGON/WINTER 2010 Figure 3 (LEFT). The decay sequences of the natural radioelements (Fajans and Soddy “Displacement Laws”), patterned after Soddy’s original list10a and graph.10b Atoms decay by emitting an ␣-particle (moving left two units and down four units) or a ␤-particle (moving right one unit). The list of natural radioelements includes some 40 members and organized into three main series: U-238, originally identified as U1 (“radium series,” the black plot), U-235, originally identified as “actinouranium” (“ series,” the red plot), and Th-232, originally identified as merely “” (“thorium series,” the blue plot). The and mass for each radioelement can be determined from the respective abscissa and ordinate. For each radioelement the original name is given (in addition to the customary elemental abbreviations, Rd = radio, Ms = meso; for example RdAc = radioactinium). (For a more complete description including half-lives of the radioelements, see reference 11).

foil.4b His discovery prompted the search for attempted to reproduce Figure 4 (ABOVE). Map of Glasgow. Sites of new radioactive elements by , who Crookes’ work, but was perplexed by his obser- interest in the University of Glasgow area: canvassed all known elements and determined vation that in his hands purified uranium was Site where Soddy proposed the concept of “isotope,” that of these only uranium and thorium exhib- still radioactive. By following Crookes’ procedure 11 University Gardens - N55° 52.37 W04° 17.45. ited activity.4b After noticing that ores of urani- exactly, Rutherford realized the discrepancy Building (modern chemistry building), um were much more radioactive than expected, was due to Crookes’ using the older Becquerel University of Glasgow - N55° 52.32 W04° 17.57 she launched her classic research with her hus- method of radioactivity detection (fogging of Lord Kelvin’s house, University of Glasgow - N55° band, , to discover and wrapped photograph plates) instead of the 52.28 W04° 17.43. radium in 1898, and her colleague André “electric method” which utilized an ionization Old Chemistry Building, Main Building, Gilbert Debierne discovered actinium in 1899.4b chamber pioneered by Pierre Curie4b Scott Building (now geography), where Soddy The discovery of radioactive elements con- (Rutherford used the Dolezalek electrometer,7 a performed his work on isotopes - N55° 52.24 tinued, which became known as the “radioele- refinement of this method 4b ). On the basis of W04° 17.25. ments.” In 1900, (1832–1919) his work at Cambridge4c where he defined ␣- — the discoverer of — made an aston- and ␤-rays, Rutherford realized that pure urani- Museum Stores, site of Soddy’s equipment and ishing observation: he found that purified ura- um (and its compounds) was an ␣-emitter models, Thurso Street - N55° 52.17 W04° 17.84. nium nitrate (prepared either by precipitation (whose rays were stopped by paper or foil) and with ammonium carbonate or by extraction that UX1 was a ␤-emitter (whose rays passed The thorium and uranium series of with ether) exhibited no radioactivity at all! 6 through Becquerel’s and Crookes’ paper wrap- radioelements (see Figure 3). Rutherford and (This puzzling observation was shortly pings). Rutherford designed an ionization Soddy turned to thorium and found it exhibit- explained by Rutherford; vide infra). Instead, chamber in which he could readily distinguish ed similar behavior. Reacting thorium nitrate radioactivity resided in the separated residue, ␣-rays and ␤-rays by alternatively using shields with ammonia (to precipitate thorium hydrox- which Crookes named uranium X, or Ur-X of 0.1 mm aluminum foil (impervious to ␣-rays) ide) gave a filtrate, which when concentrated (later named UX1). If Crookes had followed up or 5 mm aluminum foil (impervious to ␤-rays).7 gave a very active residue they called thorium- this work, he would have been the discoverer of (The third type of emission, ␥-emission was X (ThX). Careful study showed ThX in turn the natural transmutation of elements, because recently discovered by Paul Villard in 1900, transmuted into emanation (thoron), which UX1 was actually thorium-234, produced by the could be inferred by its stoppage using by 50 cm itself changed to an entire sequence of new 3 ␣-decay of uranium-238. of aluminum.7) After a period of time, an undis- radioactive products! After the Christmas hol- turbed sample of purified uranium nitrate pro- idays of 1901, Rutherford and Soddy returned The explanation of UX1 by Rutherford. Now duced a fresh supply of UX1.7 Rutherford and to study the original purified sample of thori- active in his research at McGill University Soddy determined the half-life of UX1 to be 22 um, which was found to be replenished with 4c ␤ (where he discovered the element radon) days. the -emitter ThX. Soon Rutherford and his

WINTER 2010/THE HEXAGON 69 III and anactiniumseries (AcAthrough AcD, orig- (ThA through ThD, originatingfrom thorium), originating from uranium), a “thorium series” world witha “radium series” (RaAthrough RaG, almost 40members, perplexingthescientific decades ofthe20thcentury, reaching atotalof of radioelements balloonedduringthefirsttwo University ofGlasgow(Figures 4–7). Frederick Soddy (andcolleagues)nowatthe (1887–1975; KarlsruheUniversity), and Institute, Dahlem-), KasimirFajans 1878–1968, respectively; Kaiser Willhelm Otto HahnandLiseMeiter(1879–1968 Borden Boltwood (1870–1927; Yale University), (1888–1972; Oxford University), Bertram of Chicago), Alexander Smith Russell Herbert Newby McCoy (1870–1945;University tury (Figure 3). These researchers included entists duringthefirstdecadeof20thcen- discovery ofmore radioelements by many sci- of Rutherford andSoddy sparkedthehuntand sequence: turned toradium andfoundthefollowing cade ofradioelements? Rutherford andSoddy 70 More researchersjointhehunt. sequence oftransmutations: colleague Soddy hadcarefully outlineda chemistry buildingoftheUniversityGlasgow. mounted intheJoseph BlackBuilding, themain Figure 5. This plaquededicatedtoSoddy is Did otherradioactive elementsexhibitacas- mnto 5 e) h 1 r ThA(11hr) Emanation (54sec) h(aflf 10 = Th (half-life a(50y) Emanation (4days) Ra (1500yr) a 2 i) a 4 r RaC (21 min) RaD (40 yr) a 3mn a 2 i) RaB (28min) RaA (3min) a 6dy) RaF(143days) RaE (6days) 7 9 ThB (1hr) r ThX (4yr) days) 7 The research 3, 8, 9 The list Whereas the challengeofseparating radium some ofthemembers oftheradioelements. noticed thatthere was difficultyinseparating worked theiranalyticalseparations, they through wetlaboratory chemistry. As organization oftheradioelements was found radioelements? accommodate three timesthatmany rogue was yet tobeformulated). Sohowcouldone pendent series(Bohr’s atomwiththef-subshell unusual elementsthatseemedtoformaninde- was badenoughwiththerare earths, adozen ments” intothePeriodic Table —thesituation was theimpossibilityoffittingthesenew “ele- apparent pattern. A majoradditionalproblem behavior of ley collection, whosehalf-livesandrandom elements was by meansoftheirhalf-lives. the majorway tocharacterize andidentifythese involved were generally unweighabletraces, The clueofchemicalsimilarity. It was unclearjusthowtoorganize thismot- ing withinertlead. 228), eka-tantalum(Pa-231), etc., andallend- and -2(Ra-228 Ac-228), radiothorium (Th- bers namedionium(Th-230), mesothorium1 of radon), aswelllaterintermediatemem- gases (radon, thoron, andactinon;allisotopes included three different emanationsofinert inating from uranium). These three series that flowsnearby). (Lord Kelvin, 1824–1907, named after theriver Nearby isthehistorichomeof William Thomson tivity; eventhedoorknobshadtobereplaced. and reconstructed becauseoftheintenseradioac- working space, ithadtobethoroughlyscrubbed Geography Department. When heabandonedthis Main Building. Hislaboratory nowhousesthe performed hisworkinthesoutheastcornerof Figure 6. AttheUniversityofGlasgow, Soddy ␣ - or ␤ 9 -emission exhibitedno Because thequantities The key to behavior. ings ofvirtuallyindistinguishablechemical to bepractically impossible, suggestinggroup- rating elements ofacertaingrouping appeared been “merely formidable,” theproblem ofsepa- ed outtheelementwhoseelectrochemical Oswald HelmuthGöhring(1889-?)electroplat- and several monthslaterheandhisstudent justtotherightofCrookes’ UX1— “UX2” ment boldly proposed thatthere shouldbeanele- cluster intheconstellation Taurus. Fajans then alluding tothePleiades, thewellknownstar noting atightclusterofchemicalproperties, number of had proven thechemicalidenticalnessofa Alexander Fleck(1889–1968)atGlasgowwho similar elementsina “pleiad,” radioelements inthePeriodic Table, lumping simultaneously by Fajans 1913, two definingarticlesappeared almost tively shedding from itsprogenitor tostableleadby alterna- of anatomasitfolloweditspredestined path understood. Onecouldtrace thezig-zagroute formed intooneanotherwas becoming which theseradioelements were beingtrans- movement two unitstotheleftandall which statedthatall Laws. The FajansandSoddyDisplacement dependence uponfinalanaly on extensivechemicalanalysis, withaheavy theoretical, Soddy’s conclusionswere based Laws”). Whereas Fajans’ approach was more so-called Fajans and Soddy “Displacement decays inmovement oneunittothe right(the tribution ofelements inaradioactive ore sample. the column, thesteady-state onecanvisualize dis- differently orifices;aswaterflowsthrough sized column withaseriesofchambersconnected by Stores”). This isthe “Statis machine,” which hasa machines intheHistoricMuseum(“Museum University ofGlasgow, looksupon oneofSoddy’s Figure 7. Dr. Joe Conally, ourhostatthe Curies duringtheirdiscovery ofradium from chemicallysimilarbarium (solvedby the In his1913articles, Meanwhile, theroadmap (Figure 3)by ␤ -emitters. THE HEXAGON/ ␣ - and 14 12b Fajans organized the ␣ ␤ -decays resulted in 12b -particles. Inearly sis ofhisstudent WINTER 2010 12b and Soddy, a namecon- 4b ) had 13 ␤ - Figure 8. This is the main building of the University of Karlsruhe, 12 Kaisserstrasse; the original building of Universitat Fridericiana Figure 9. Building (Thielallee 63 - N52° 26.85 E13° 17.11), of the present Freie Universität of (N49° 00.56 E08° 24.72), where Lothar Meyer Dahlem, , previously the Kaiser Wilhelm Institute, where Otto Hahn and discovered refined his . Behind lay the Chemical protactinium-231.24 As has been done with so many buildings in Berlin, this edifice was extensively dam- Institute (Kollegium) where Kasimir Fajans dis- aged in World War II but was reconstructed to closely replicate the original architecture. The building is 15 covered “brevium” (Pa-234m), the first isotope of now used for biochemical studies. Much important history has occurred here, including the discovery of element-91 in 1913 (now Kollegiengebäude der (announced by the plaque attached to the turret, seen here to the right). On the second étage Ehrenhof, Englerstrasse 11 - N49° 00.61 E08° (third floor) is the Lise Meitner Hörsaal (lecture hall). 24.72). Nearby is the Ständehaus, where in 1860 the international Chemical Congress was held, was resolved: different radioelements could be “smoothed over the rough edges of isotopes”9 which inspired the conception of Dimitri simply lumped into preexisting boxes. The term when his method of X-ray spectroscopy was 4a Mendeleev’s and Lothar Meyer’s Periodic Tables. Soddy coined—isotope— was fully intended to expanded by Karl Manne Siegbahn (1886–1978, convey the meaning that two species resided at Nobel Laureate in in 1924) to include potential placed it in this vacant space (Figure the identical location in the Periodic Table, even the atomic number of uranium. Siegbahn 8).15 This element could be detected because of if they had different atomic masses and half- showed that even though uranium was com- its high activity, with a short half-life of 1.17 lives. Soddy was proposing an astonishing con- posed of several isotopes (Note 3), nevertheless minutes, even though ponderable quantities cept: A specific element, which historically was the element appeared to exhibit a clearly could not be collected. Because “it was the only once considered not fully characterized without defined atomic number.18 The method of mass element in the 5th group of the last row,” he felt a specific , now could be variable in spectrometry, developed by Francis William justified in giving it a name, “brevium”16 (now its mass! Aston (1877–1945, Nobel Laureate in chemistry known to be protactinium-234m) (Note 1). in 1922), soon allowed the direct observation of Fajans in his studies was using an electro- Corroboration of the predicted different isotopes and he wrote the definitive article on plating technique whereby he could plate out masses for isotopes. It remained to prove that the , , and other traces of specific radioelements and could char- chemically identical elements did in fact have radioactive elements.19 Even Fajans, who had acterize each by determining its half-life. By different masses. According to both Fajans and long viewed each radioelement as a “new ele- contrast, Soddy was using wet laboratory pro- Soddy, lead (Pb) from different decay ment,” by 1923 had abandoned his concept of cedures and was impressed with the apparent sequences should have different atomic mass- the scattered pleiads and had accepted the view impossibility of chemical separation of various es. Fajans took the initiative and sent his stu- that isotopes should be tightly boxed in indi- radioelements. Soddy considered the elements dent Max Ernest Lembert (1891–1925) to the vidual cubicles of the Periodic Table.20 of a grouping not “a scattered pleiade,” but as laboratory of Theodore William Richards chemically identical. While Fajans had grouped (1868–1928) at Harvard University, the recog- Epilogue—the construction of the nucleus. the radioelements loosely in a table,12a Soddy nized expert in atomic mass determinations. What was the genesis of the different isotopes drew a precise two-axis graph.13 Soddy under- Richards and Lembert repeated the atomic of an element? The prevalent view during the stood the implications of chemical indistin- mass determination for ordinary lead and first quarter of the twentieth century was that guishability— for example, ionium (Th-230, the reproduced the published value of 207.15. Lead the nucleus was composed of and a precursor to radium in the uranium sequence) from uranium samples from around the world lesser number of that partially neu- was identical to native thorium (Th-232) (Note gave a value ranging from 206.40–206.82,17 a tralized the positive charge, but it was not 2), even to the point of identical spectra,13 value soon confirmed in three more laborato- known where these electrons resided. Fajans despite their different half-lives (7.54 x 104 and ries. There was no doubt about it—lead from thought all electronic processes (either chemi- 1.40 x 1010 years, respectively). If one believed radioactive sources was lighter than ordinary cal redox or nuclear decay) must occur in the Soddy, then the disconcerting problem of stuff- lead, and there proved to be no spectroscopic same region of the , since the particles ing too many elements into the Periodic Table differences. Later, the method of Moseley 4d (continued on page 74)

WINTER 2010/THE HEXAGON 71 III right oftheemanationpleiad(radon) 227). Fajans alsopredicted apleiadjusttothe Ac- was theprecursor toactinium(Pa-231 Aberdeen (Figure 10), and namedbecauseit Catherine Perey (1909–1975). minutes was discovered in1939by Marguerite fied whenfrancium withahalf-lifeof21.8 (Figure 9)andSoddy andCranston behavior. mies hemadeinthescienceworld by hisbrash Prize, perhapsinpartowingtopoliticalene- celebrated career butnever received theNobel t siia success” its “suicidal understanding, thestory ofradiochemistry with radioelement decay sequences. With this emerged oftheatomanditsbehavior inthe in ments. This shallbethetopicofafuture article Chemistry” andthebirthofartificialele- “Nuclear the way forthenextchapter— tion oftetravalent uranous togivehexavalent electronic structure, ton/ ratio. With Bohr’s descriptionof a ) inspecialcasesdefinedby alow pro- particle thatcouldejectanelectron (tobecome proton andanelectron, butan entirely new tral particlewas notsimplyacombinationof who discovered (1891–1974, NobelLaureate inphysics in1935), trons was solvedby “nuclearelectrons.” thing specialabout be cleanlyseparated. Clearlythere was some- butinsteadthey could — chemically identical identical processes, thenUX1andU2shouldbe tion) andbetaloss() were U2 (Th-234U-234). Ifelectron loss(oxida- sequences was firstproposed by Auguste tope ofuranium givingrisetoadditional decay Urey in1931by distillation ofliquidhydrogen point energy; deuteriumwas discovered by mass canbeasignificantdifference inthezero- properties, particularlywhere asmallatomic topes independently by HahnandMeitner isolated inweighablequantitiesfouryears later, “Protactinium” (Pa-231) was discovered and 74 decay G. N. Lewis usingelectrolysis. and pure heavy water was prepared in1933by Notes. nuclear electrons. clear difference betweenorbiting electrons and argument ofSoddy in1913underscored the (electrons) were identical. However, alogical ( uranyl (U The HEXAGON Rediscovery The answertotheriddleofnuclearelec- Note 3. The possibilityofmore thanoneiso- Note 2. Ironically, itwas laterfoundthatiso- Note 1. “Brevium” was Pa-234m. of UX1, whichlosestwo electrons toform can 27 have different chemicalandphysical 4+ 22 continued frompage71) the neutron in1932. This neu- 21 “Rediscovery” series. Soddy compared theoxida- U 9 23 6+ was completed, paving ) withtheradioactive a completepicture 29 26 Fajans hada 24 12 in Berlin veri- — 25 in 28 ately realized tral work of Aston, mass of235was establishedby themassspec- incorrectly suggestingamass of239;thecorrect Nobel address. um serieswas acknowledgedby Soddy inhis ring isotopeofuranium givingrisetotheactini- ratory). Piccard’s conceptofanaturally occur- mass of231(promptly verifiedinHahn’s labo- Hahn andSoddy independently)would have a 0 F. Soddy, 10. .F. Soddy, “The origins oftheconception 5. .L. Badash, 9. F. Soddy andJ. A. Cranston, 8. 7. E. Rutherford, 6. W. Crookes, F. Soddy, 2. Personal communication, Professor Alan 1. References. .J. L. Marshall and V. R. Marshall, 4. M. Howorth, 3. isotopes,” Nobellecture, Dec. 12, 1922. Longsmans, Green & Co., New York. (a) 245–256. 42–47. (c) Publications, Westminster. [lectures delivered 1953–1954], New World Lectures bySoddy andCranston 1906 66 1951 (alsodescribedinlessdetailref 8). p.m. 14June,interviewed, broadcast 10:30 “Science Survey” where Soddy was manuscript ofaB.B.C. radio program, University ofGlasgow;whofurnisheda Cooper, DepartmentofChemistry, 2006 The HEXAGON ofAlphaChiSigma London. Soddy 1917, heproposed flights) anddeepsea(bathyscape) fame. In Piccard (1882–1962)ofhigh-altitude (balloon , 409. 2010 Part I , UniversityPress, . , , 97(4) 1958 , 31 , 101(2) The chemistryofthe radio-elements, Nature 1911 5 that protactinium (discovered by , 50–55;(b) Brit. J. His. Sci. , New World Publications, Proc. Roy. Soc. (Ser. A) 30 The LifeStoryofFrederick 19 , and(b) an elementactinouranium, Radioactive Transformations , 22–26;(d) and Rutherford immedi- , 1913 , 2010 92 Part II , , 399–400. 1979 2010 , 101(1) Isotopy. , , 1914 , 1954 , 12 101(3) , , , (a) , 6–11; 1900 , , , , , 1 E. Rutherford, 31. A. Piccard, 30. 29. G. N. Lewis andR. T. MacDonald, R. T., 8 H. C. Urey, Ferdinand G. Brickwedde,28. and 27. L. S. Bartell, M. Perey,26. F. Soddy andJ. A. Cranston,25. 4 O. HahnandL. Meitner, 24. 3 J. L. Heilbron, 23. 2 J. Chadwick, James, 22. F. Soddy, 21. F. Fajans, 20. elements 161–164. J. Chem. Phys. 164–165. 62–63. G. M. Murphy, (London) 1918 147–228. Genesis oftheBohr Atom,” Arno Press, Theory ofAtomicStructure 692–708. 312; developments inthestudy ofthechemical 9 F. W. Aston, 19. 8 K. Fajans, 18. 7 T. W. Richards andM. Lembert,17. 4 A. Fleck, 14. F. Soddy, 13. K. Fajans, 12. 6 K. Fajans, 16. 5 K. Fajans andO. H. Göhring, 15. 1 J. L. Marshalland V.11. R. Marshall, , Proc.Roy. Soc. Braunschweig. Elementen Entwicklung derLehre vondenchemischen Chem. Soc. 3486–3497. 131–136; (b)136–142. Sketch ofDiscoveries,” 101–113. ISBN 978-0-615-30793-0, “Historical Zeitschrift Rediscovery oftheElements 19 THE HEXAGON/ , , 208–218. , 1923 Nature 1918 Comptes rendu. Radioactivity andthelatest Arch. sci. phys. nat. until hemovedhere in 1917. objective wasnotcompleted in Glasgow, hisfinished eka-tantalum hadbeendone preliminary workon W02° 05.81). Althoughsome (Broad Street, N57°08.93 (protactinium-231) in1917 Bull. Hist. Chem. discovered Soddy independently in Aberdeen, Scotland, where Figure 10. MarischalCollege , , Metheun&Co., London, xii. , J. Chem. Soc. Historical Studiesinthe 1933 Nature , Chem News , Phys. Rev. 94 Radioaktivität unddieneueste Phys. Zeitschrift Ber. deutsch. chem. Ges. , 1913 1920 , 1914 1913 Nature , 384–404. , 1932 , Nature 1 , , Friedr. Vieweg &Sohn, , , , 341-344. 25 14 , 1929 36 92 “eka-tantalum” , , 877–84. , WINTER 2010 , , 3 (SerA) 136 , 1329–1344. Phys. Zeitschrift , 1939 1929 , 399–400. 1932 , 1981 , , , 1913 1913 1932 123 , Proc. Roy. Soc. , 2010 , , 123. 1917 , , , [DVD], , “The 208 , 313–314. 1913 39 , , , 107 103 129 , , , 97–99. Phys. , 35(1) , 44 , 14, (a) , 97–99. , 381–399. , , J. Amer. 1913 , 2010 , , , 46 , ,