Rediscovery of the Elements Moseley and Atomic Numbers

ing the Industrial Revolution which brought wealth and prosperity to the community. By the mid-1800s, was the second largest III city in and gained a reputation as a center of invention and technological progress. In 1781 a prestigious scientific institution was founded— the Literary and Philosophical Society (commonly known as the “Lit. and Phil.”).1 In this society John (1766–1844),2a who arrived in Manchester in 1793, formulated his at the turn of the century.3 At the very same platform4 where Dalton proposed his idea of and James L. Marshall, Beta Eta 1971, and atomic masses (Figures 1, 2), Virginia R. Marshall, Beta Eta 2003, one century later first proposed the nuclear Department of , University of , a dense positive core surrounded by elec- 5 North Texas, Denton, TX 76203-5070, trons. Ernest Rutherford had arrived in 1907 from [email protected] McGill University, Montreal, Canada.2d At the (then named the Introduction. Manchester in northwest Victoria University of Manchester) he assem- England was founded as a Roman fort in 79 bled a powerful team of gifted individuals Figure 1. This was the Literary and Philosophical A.D. After the Roman departure it evolved into including an graduate named building at 36 George Street in Manchester built in a typical Medieval village and after a millenni- Gwyn-Jeffreys Moseley (1887–1915), who 1799 which served the scientific community for 140 um matured into a manufacturing giant. An joined the group in 1910. During 1913–14 years before being destroyed in a German bombing influx of Flemish wool and linen weavers in the Moseley published two papers which estab- raid in December 1940. Here the main meetings of 14th century, followed by a developing supply lished the physical basis of the atomic number the Lit. and Phil. were conducted, including the cen- of cotton from India and the American South in and resolved several long-standing problems tury-apart presentations of Dalton’s atomic theory the 1700s, launched a large textile industry dur- (continued on page 44) and Rutherford’s nuclear atom.4

Figure 2. Today the site at 36 George Street in Manchester is occupied by Devonshire House, used for University functions. A (left, on wall and shown below) reads: “John Dalton (1766–1844), Founder of the scientific Atomic Theory, President of the Manchester Literary and Philosophical Society, had his laboratory here.”

42 THE HEXAGON/FALL 2010 Figure 5. Oxford, England. ASHMOLEAN MUSEUM OF ART AND ARCHEOLOGY, Beaumont Street– N51° 45.31 W01° 15.00. MUSEUM OF THE HISTORY OF , displays of Moseley and others, Figure 3. Right: Moseley’s X-ray plots (“Moseley’s law”) establishing the Broad Street– N51° 45.26 W01° 15.33. validity of atomic number, N, as published in “High Frequency Spectra of the Elements, Part II”.15 This plot is displayed in the Moseley Room of Lindemann ROBERT BOYLE, site of original house, High Street, plaque– N51° 45.16 W01° Hall (physics building) of Oxford University. The ordinate is atomic number 15.15. N, with elements identified, ranging from aluminum to gold; the abscissa is FRANCIS BACON, site of original home, Old Greyfriars Street, plaque– N51° the square root of the X-ray frequency. The upper series of the plots are L- 45.01 W01° 15.64. lines; the lower are K-lines. The elements included are Al, Si, Cl, K, Ca, Ti, V, MUSEUM OF NATURAL HISTORY, several statues and Lewis Carroll exhibit, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Sb, La, Ce, Pr, Nd, Parks Road– N51° 45.51 W01° 15.36. Sm, Eu, Gd, Ho, Er, Ta, W, Os, Ir, Pt, Au. Expansion at left: Notice the confu- TOWNSEND HALL (Electrical Building), Physics Department, laboratory of sion of elements 70, 71, 72, misidentified by Moseley as “thulium II,” “ytter- Moseley, Parks Road– N51° 45.56 W01° 15.39. bium,” and “lutetium”; these were not corrected until he analyzed Urbain’s samples (in May 1914; see text) and until hafnium (72) was LINDEMANN HALL, Physics Department, Moseley Room with original discovered in Copenhagen (in 1923). apparatus and memorabilia, Parks Road– N51° 45.59 W01° 15.41.

Figure 4. Manchester, England landmarks, including those not only for Rutherford and Moseley, but also Dalton and Roscoe (discussed in previous HEXAGON articles 2a,c):

OWENS COLLEGE (now a barrister’s office building), where Roscoe first prepared metallic vanadium, N53° 28.72 W02° 15.12. TOWN HALL, marble statues of Dalton and , Ford Maddox Brown’s famous mural paintings portraying the , including one of Dalton collecting marsh ; Albert Square–N53° 28.77 W02° 14.66. LIT. & PHIL. (Literary and Philosophical Society), destroyed in WWII raid (December 1940); now Devonshire House, 36 George Street, blue plaque– N53° 28.76 W02° 14.38. MANCHESTER METROPOLITAN UNIVERSITY, site of Dalton bronze statue, Chester Street– N53° 28.32 W02° 14.44. UNIVERSITY OF MANCHESTER: [OLD] COUPLAND 1 BUILDING (now called Rutherford Building), site of Rutherford’s and Moseley’s pioneering studies, Coupland Street– N53° 27.96 W02° 14.08. UNIVERSITY OF MANCHESTER: COURTYARD, University of Manchester, WWI tribute to Moseley– N53° 27.93 W02° 14.05.

FALL 2010/THE HEXAGON 43 III ters of mass) orof might includesomefunctionof experiments atManchester ofRutherford and basis ofthefamous alphaparticlescattering and Hevesy inJune 1913 at Manchester ing aconversation ofMoseley, Darwin, Bohr, weknowwere discusseddur- —which meters property oftheelement. These physical para- frequency oftheseemittedX-rays toaphysical he would explore thepossibilityofrelating the ly namedtheKandLshells). Moseley decided the lowesttwo atomicelectronic levels, logical- to arisefrom electrons fallingtovacancies in pattern whenpassedthrough acrystal. (1890–1971) thatX-rays generated adiffraction covered by William lines (“soft” radiation) named themK-lines(“hard” radiation) andL- of themetal;hehadobserved two seriesand would emithomogenousX-rays characteristic a metaltarget whenbombarded by electrons Glover Barkla(1877–1944)haddiscovered that mulated anew research idea. In1906Charles Röntgen in1895). phenomenon ofX-rays (discovered by Wilhelm radioactivity, buthewas intriguedby thenew Oxford. Moseley was assignedaproblem in Rutherford’s group aftergraduating from physics program atManchester, hejoined original research. Impressed withthesuperior degree. at Oxford where in1910hereceived hisM.A. famous EtonCollegeandthen Trinity College known as “Harry” by hisfriends)attendedthe tion of1872–1876. The young Henry (whowas the H. M. S. Challengeroceanographic expedi- University; hewas partof the scientificstaffof in 1891)was aprofessor ofbiologyatOxford of conchology(mollusks). Hisfather(whodied trained asabarrister butlaterpursuedhislove King’s College, andhismaternalgrandfather been afamousmathematicianandphysicist at scientific family. Hispaternalgrandfather had 44 rays from crystal surfaces. they investigated thebehavior of reflected X- tiated anX-ray investigation ofmetals, where famous CharlesRobertDarwin1809–1882)ini- Galton Darwin(1887–1962;agrandson of Manchester, Henry Moseley andCharles in 1915forX-ray spectroscopy). Backin son William Lawrence received theNobelPrize art ofX-ray analysis(father and William Henry Bragg (1862–1942)tolearnthe Moseley traveled toLeedsthelaboratory of which oneswere yet tobediscovered. ordering ofelementsand predict specifically discoveries onecould nowestablishthecorrect concerning thePeriodic Table. With Moseley’s Meanwhile, Moseley hadindependentlyfor- A natural experimenter, Harry wanted todo Henry Moseley camefrom adistinguished A and 7 Z (nuclear charge). These parame- Z had beendevelo 6a In July of1912itwas dis- 9 (these are nowknown 6a ped onthe A 6a (atomic 6a — 8 experiments suggested the for Rutherford’s nuclearatom. ment’s positioninthePeriodic Table might Broek (1870–1926), had proposed thatanele- lowest elementsofthePeriodic Table, .” laboratory 1907–1919—Herein discovered thenuclear atom, splittheatom, andinitiatedthefieldof his distinguishedteamofnuclearpioneers. Aplaqueonthebuildingreads: . . .“Ernest Rutherford ledthis known atfirstastheSchusterBuildingandthenCouplandIBuilding. Here Rutherford assembled Figure 6. The Rutherford BuildinginManchester. This wastheoriginalphysics buildingopenedin1900, An amateurDutchscientist, Anton van den Ernest Marsden(1889–1979) 10 that, atleast forthe , theoriginal basis 6b The scattering Z = A /2. selected elementsthrough uranium, notation proposed definitevalues for electronic configurations. Broek actuallyput employing assumed(butincorrect) pre-Bohr ed by theuseofformulashecontrivedwhile reflect this “intra-atomic charge” of M , for “Mendeleev’s number”) for THE HEXAGON/ Z (he preferred the Moseley’s entry. Inset atbottom: Engineers. member oftheRoyal dead.” Moseleywasa a littlehourandisnot his eternitywith brance. Hehasbrought and enduringremem- 1914–1919. Ingrateful in theGreat War of who laiddowntheirlives Officers TrainingCorps Manchester andofthe bers oftheUniversity inscribed: “To themem- Hall. Inthecenteris courtyard of Whitworth War IMemorialinthe Honor andthe World Figure 7. The Rollof FALL 2010 11 calculat- 11 Broek Z . Figure 9. Royal Society of Chemistry (RSC) plaque mounted at entrance of Townsend Hall. Figure 8. Townsend Hall, where Moseley performed his research in Oxford. This building presently lies The Clarendon Laboratory of physics encompasses 100 m north of the Museum of Natural History which includes specimens of a dodo, a flamingo, and other Townsend and Lindemann Halls. Courtesy, Jim creatures which inspired the creatures in Lewis Carroll’s (Charles Lutwidge Dodgson 1832–1898) Alice in Williamson, Emeritus, Atmospheric, Oceanic Wonderland. Townsend Hall was originally known as the Electrical Science Building, built in 1910, just in and Planetary Physics, University of Oxford. time for Moseley to continue his X-ray studies in 1913. It is, unfortunately, not known which laboratory inside the building he used. Next door (north) is Lindemann Hall (not shown) with the Moseley Lecture probably get lost on my way to the College; it Hall with a small display on Moseley (see Figure 3). This photograph was taken in 2001; in 2007 a plaque tastes acrid and tickles the throat ... . Monday was mounted by the door (see next figure). the fog was thinner but more yellow. Sunday it poured all day... .”7 Also, he was apparently forward correct values through 50, but then fell 1/12 –1/22 term already observed in Rydberg uneasy in the less formal industrial culture and into error for the heavier elements, e.g., W = 78, expressions, and the “1” in the (N - 1) term was mixed student body of Manchester, perhaps Au = 83, U = 96 (instead of correct 74, 79, 92, rapidly identified as the shielding effect of inner “feeling himself above students, even equal respectively). But before Moseley’s work, no electrons.12 Moseley pointed out that his work with Rutherford, whose tea-time conversation one knew how to get at an independent mea- clearly established that indeed nickel had a of slang, banter, and wisecracks he judged more sure of this intra-atomic charge. higher atomic number than cobalt. The confi- suitable to a caricature of a colonial rather than Moseley’s goal was specific: “My work was dent Moseley unequivocally stated: “We have a professor of physics.”10 Whatever the reasons, undertaken for the express purpose of testing here a proof that there is in the atom a funda- the motivation to return to Oxford was strong, Broek’s hypothesis . . .“12 Moseley had gained a mental quantity, which increases by regular because he departed Manchester immediately reputation of perhaps being the only one to steps as we pass from one element to the upon finishing his work, even though no equal Rutherford’s hard work, drive, and next. The quantity can only be the charge on appointment awaited him in Oxford. results;7 and by the fall of 1913 he had obtained the central positive nucleus, of the existence Once settled in Oxford, Moseley was given the K-line spectra of the series calcium (20) of which we already have definite proof.”13 access to a laboratory in the Electrical Science through zinc (30) (excepting the scarce element Moseley went on to predict: “It [the correla- Building (physics building), and by private scandium, 21). Accurate measurements were tion of X-ray spectra with N] may even lead to means he assembled equipment to continue his possible because of the preparatory collabora- the discovery of missing elements, as it will be research (his X-ray tube had been broken and a tive work with Darwin. The calcium-zinc series possible to predict the position of their char- new one needed to be constructed). By April of included the perplexing pair nickel and cobalt: acteristic lines. . . .”13 1914, he had gathered data from additional nickel had a lower , but its chemi- The next step in Moseley’s research was to lower elements using K-lines as well as higher cal behavior more closely resembled the higher produce the X-ray spectra of the higher ele- elements using L-lines. The equation for the L- 2 family including palladium and platinum. ments. But Moseley performed no more work alpha lines was /0 = 5/36 (N-7.4) , where 5/36 Moseley’s results were dramatic and simple, at Manchester. In November of 1913, after writ- was recognized as the Rydberg expression 1/22- which he described in an article entitled “The ing his seminal paper,13 Moseley returned to 1/32 and 7.4 was an electron shielding factor. In High Frequency Spectra of the Elements.”13 He Oxford. It is apparent that he was homesick for all he was able to establish unambiguously Z found that the frequency of K-alpha (the “The City of Dreaming Spires” with its more values for 38 elements in a range from alu- strongest line) was accurately described by the scholarly atmosphere, and he wished to be minum (13) to gold (79) (Figure 3) which he 2 6a equation /0 = 3/4 (N-1) , where 0 was the closer to his widowed mother and the oppor- presented in his second paper, “High Frequency Rydberg frequency (previously developed in tunities of the countryside where he had spent Spectra of the Elements, Part II.”15 Again, his spectroscopic studies) and N was a number many pleasant years pursuing bird-nest collect- plot clarified the situation of “odd pairs”— termed “the atomic number” by Moseley (and ing and other hobbies.7 A letter to his mother lighter potassium had a higher atomic number perhaps jointly with Rutherford).14 The 3/4 from Manchester gives an insight to his feel- than argon, and lighter iodine had a higher coefficient was recognized by Moseley as the ings: “Today the fog is so thick, that I shall atomic number than tellurium (the iodine-tel-

FALL 2010/THE HEXAGON 45 III determined Siegbahn (1886–1978;NobelLaureate 1924) the Swedishphysicist KarlManneGeorg elements beyond gold(79)buttwo years later yet to bediscovered. Moseley did notanalyze location ofthetruegapswhere elementswere atomic numbersunequivocallyidentifiedthe 69–71; seecaptiontoFigure 3). And lastly, his sion withthelighterrare earths57–68(butnot Furthermore, Moseley’s plotremoved confu- HEXAGON (1813–1915) (respectively discussedinprevious to John DaltonandHenry EnfieldRoscoe Manchester are alsoincludedlocationsrelating presented inFigures 4and5. Inthemapfor eries, ManchesterandOxford, have theirmaps can (anddo!)claimcredit forMoseley’s discov- used by theDepartmentofPsychology, but Manchester. The Rutherford Buildingisnow Building, located atthepresent University of nowcalledtheRutherford building CouplandI, laboratory (Figure 6)was originallythephysics combatant. the factthathecouldhave served asanon- England andwas determinedtoenlist, despite I broke outin August, Moseley returned to British Association. WhenWorldthe of ing War Australia, where heattendedtheannualmeet- of 1914hetraveled toCanada, theU.S., andto work Moseley performed. Duringthesummer technique. pointed butamazedatthepowerofMoseley’s (hafnium). Urbainreturned toFrance disap- gaps remained at61(promethium) and72 butnotrace ofceltiumwas found, and 3)— regarding theheavier rare earths(seeFigure Moseley’s X-ray analysisremoved confusion crystallization schemes formany years. totally occupiedhisattentionwithlaborious thesampleswhichhad lyzed inonesession— “flabbergasted” covery ofanew rare earth “celtium.” Hewas of Urbain’s goalswas toverifyhistentativedis- technique andvisitedhiminMay of1914. One of lutetium, heard ofMoseley’s remarkable inParis and oneoftheco-discoverers 87 (Tc, Pm, Re, At, andFr, respectively). would bediscovered with establishing theprediction that future elements of thenatural elements withatomicnumber92, Turkey, hewas killed August 10, 1915. in June 1915. At thetragic BattleofGallipoliin Engineers andwas shippedtotheDardanelles 46 Rediscovering Moseley. Rediscovering mass determinedfortelluriumwas incorrect! resolved thedifficultyby assumingtheatomic accordance withtheirchemical properties; he Mendeleev reversed telluriumandiodinein lurium problem hadexisted since1871, when Urbain’s analyseswere thelastlaboratory Georges Urbain(1872–1938), arare-earth articles 7 16 He was commissionedintheRoyal that uranium lay atthehighend 10 that hissampleswere ana- 2a,c ). The siteofRutherford’s The two citieswhich N = 43, 61, 75, 85, and 2b ). been broken(onexhibitintheLindemannHallMoseleyRoom). Figure 10. X-tubeusedbyMoseleyinOxford, constructed there since the oneheusedatManchesterhad and Ihadtomakeeverythingmyself.” the apparatus tookalongtime, asthelaboratory assistantspenthistimemendingRutherford’s motorcar, designed andprepared hisownequipment. HeoncewrotetohismotherwhileatManchester: “Remaking earlier stayatOxford, before hewenttoManchester. Moseleywasabrilliantexperimenterandcustomarily Figure 11. This istheclassicphotograph ofMoseleyin1910, intheBalliol-Trinity laboratories duringhis collections atthe Ashmolean Science Museum (physics building) Moseley Room, aswell exhibit attheadjoiningLindemann Hall posted onthisbuildingin2007(Figure 9). An ing) (Figure 8). A tribute was erected tohimand research atthe Townsend Hall(physics build- (Figure 7). At Oxford Moseley performedhis memorial whichincludesthename ofMoseley University ofManchesteristhe World War I Rutherford there. At themainCourtyard atthe present plansincludedeveloping anexhibiton 7 see actuallytheRutherford work [thenuclear interview in 1962, NielsBohrexplained: “You ing acceptabletoallscientists. Inapersonal istry, andputRutherford’s atom onafirmfoot- In two papersheinterlacedphysics andchem- the importanceofMoseley’s work (Figure 11). Moseley’s Legacy. ies (Figures 3, 10). equipment andapparatus heusedinhisstud- in Oxford, includealarge portionofMoseley’s THE HEXAGON/ It isdifficulttooverestimate FALL 2010 atom] was not taken seriously. . . . There was no name is memorialized by the inscription on the mention of it in any place. The great change Helles Memorial (N40° 02.81 E26° 10.68) at the came from Moseley.”7 When Urbain had visited southernmost tip of the Gallipoli Peninsula, 23 Moseley in May of 1914, Moseley was aston- km south of the Anzac Cove Memorial.21 ished to find that Urbain did not care to under- stand the origin of the X-ray K- and L-lines.7 References. Urbain had not the slightest curiosity of why 1. R. H. Kargon, Science in Victorian Manchester, Moseley’s law worked.7 Moseley marveled, 1977, Johns Hopkins University Press, “Where we try to find models or analogies, they Baltimore, Maryland, 2–10. [Continental scientists] are quite content with laws.” But soon it became apparent that the 2. J. L. Marshall and V. R. Marshall, well-known British need for “the robust form The HEXAGON of Alpha Chi Sigma, (a) and vivid colouring of a physical illustration”7 2006, 97(4), 50–55; (b) 2007, 98(2), 23–29; was perfect for the times—and it was Moseley’s (c) 2008, 99(3), 42–46; (d) 2010, 101(2), discoveries that persuaded the Continental sci- 22–26. entists that the “childish British” atomic mod- 3. John Dalton, A New System of Chemical els10 were in fact real. Philosophy, 1808, Manchester. Moseley performed his famous work on his 4. Personal communication, Allan Jefferies, law of atomic numbers during a period of about Administrator, Lit. & Phil. Soc., eight months. There is little doubt that if he had Manchester. lived, he would have become a Nobel laureate 5. E. Rutherford, Proc. Man. Lit. Phil. Soc., before the other members of Rutherford’s 1911, 55, xviii-xx. team —Soddy, Hahn, Bohr, Hevesy.10 With 6. J. L. Heilbron, Historical Studies in the Moseley’s passing, both sides of the Great War 7 Theory of Atomic Structure, 1981, Arno mourned. Asimov remarked, “In view of what Press, (a) “The Work of H. G. J. Moseley,” he might have accomplished (he was only 27 229–364; (b) “The Scattering of and when he died), his death might well have been Particles and Rutherford’s Atom,” 84–145. the most costly single death of the war to mankind generally.”17 Moseley’s death prompt- 7. J. L. Heilbron, H. G. J. Moseley. The Life and Jenny and Jim Marshall ed Rutherford and others to convince the pub- Letters of an English , 1887–1915, lic and the British Ministry of Defence that sci- 1974, University of California Press. entists should be preserved in wartime since 8. W. L. Bragg, Proc. Cambridge. Phil. Soc., Rediscovering they are an asset not only to the public at large 1913, 17, 43–57; Nature, 1912, 90, 410. The Periodic Table, 7 but to the military. 9. C. G. Barkla, Phil. Mag., 1906, 11, 812–828. But beyond this, Moseley’s death represents One Element at a Time 10. J. L. Heilbron, Ernest Rutherford and the so much more. Mustafa Kemal Atatürk Explosion of Atoms, 2003, Oxford Shortly after getting married 12 years (1881–1938), Turkish leader at the Battle of University Press. ago, Jim Marshall, a chemistry professor Gallipoli and founder and first president (1923) at the University of North Texas, took his 18 11. A. van den Broek, Nature, 1911, 87, 78; of the Republic of Turkey, lamented the futility new bride Jenny, a now-retired middle 1913, 92, 372–373; 1913, 92, 476–478. of war—his words are inscribed on the Anzac school computer teacher, on the honey- Cove Memorial (N40° 14.32 E26° 16.62), over- 12. H. Moseley, Nature, 1913, 92, 554 [received moon of a lifetime. Together, they set out looking the main staging area in the Gallipoli Jan. 5, 1914]. in search of the birthplace of each of the 19 Campaign: “Those heroes that shed their 13. H. G. J. Moseley, Phil. Mag., 1913, 26, 114 elements blood and lost their lives. . . . You are now lying 1025–1034. on the periodic table. They’ve finally in the soil of a friendly country. Therefore rest in 14. E. Rutherford, Nature, 1913, 92, 423. completed their journey and compiled a peace. There is no difference between the comprehensive Johnnies and the Mehmets to us where they lie 15. H. G. J. Moseley, Phil. Mag., 1914, 27, 703–713. interactive DVD called “Rediscovery side by side here in this country of ours. . . . You, of the Elements.” the mothers, who sent their sons from far away 16. M. Siegbahn and E. Friman, Phil. Mag., countries wipe away your tears. Your sons are 1916, 31, 403–406. “Rediscovery of the now lying in our bosom and are in peace. After 17. I. Asimov, Asimov’s Biographical Encyclopedia having lost their lives on this land they have of Science and Technology, 1964, Doubleday Elements” featured on become our sons as well.” Atatürk’s evocative & Company, 512–513. PRI’s “Here and Now” words truly apply to Henry Moseley. Of the ca. 18. A. Mango, Atatürk, 2000, Overlook Press, There is a wonderful segment of PRI’s 130,000 Allied and Turkish personnel who per- Woodstock, N.Y. “Here and Now” that ran on September ished in this campaign April 25, 1915—January 8, 2010, featuring an interview with Jim 19. B. Scates, Return to Gallipoli, 2006, 9, 1916—an attempt of the Allies to control the and Jenny Marshall, creators and authors Cambridge Univ. Press, Cambridge UK. Dardanelles straits leading to Istanbul of the popular “Rediscovery of the (Constantinople)20 — virtually all are buried on 20. E. W. Bush, Gallipoli, 1975, St. Martin’s Elements” series. http://www.hereandnow. the Gallipoli peninsula, and a major portion of Press, N.Y. org/2010/09/rundown-98-2/ these lie in unidentified graves, including, as far 21. Records of the Commonwealth War Graves as anyone knows, Moseley. Henry Moseley’s Commission, http://www.cwgc.org/.

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