UCRE /a2 6 p// c.2 1 NIVERSITY OF CALIFORNIA AIJC 2 1 1987 LIBRAr-cY ~i\ili DOCUMENTS SECTION TWO-WEEK LOAN COPY This is a Library Circulating Copy which may be borrowed for two weeks. BERKELEY, CALIFORNIA Issge.3 to: I--- +qy-q- 't v - 3 a,.D zackl person who recejvoz this 3ocu;nent mist si!;~the covt-r spscfr below. _ ._ _ ___ _-.__. _- - -- - --.- - - -. -.. -. .. --- __.____________ .- -..- ^ _ -.___ _-- Route to iioted by Date Routo to ?310tedby Data . _--....... _. ._ ._ -__--_ ___. -__------.- -.---- --------.------ - I I --.- -- .-- !- -- I , ! ! I i I I . - -. -- - -- +------- -- --.-- -C*-- .-L --.--.--- -I I i I I +i --------. -- ! I , . i / -. L-...--I--.-.--. r.-.-- ---- - .. - --- -- -- - i -.I_ ____I-_ -. t I .--. -. J I i- .- ..--..- I _--.-- , I ..-- i I I -- I I .- -- - --- _ -- .---. i ! ---- I - UNIVE3.S ITY OF CALIFORNU RADIATION LABORATORY CLIWFICATION CANCELLED *i''(i.iRiTl' OF THE DECLASSIFICATION T.' ); " (1 * EC 7 , p7lb tllb c**g ld&z& LC- <-J-6 i .L * \, > .' p{E 1'-n CJN MALING THE DATE CHANGE ELECTRONIC STRUCTURE OF TIE HEAVIEST ELSNm By G, T. Seaborg July 10, 1948 ~e&le~,California UCRL 102 Chemistry-Transuranic Elements Standard Distribution --No. of Copies Argonne National Laboratory Atomic Energy Commission, Washington Brookhaven National Laboratory General Eleatrio Company Hanford Directed Operations Iowa State College Kellex Corporation Los Alamos Naval Radiological Defense Laboratory NEPA New York Directed Operations Oak Ridge National Lotboratory Patent Advisor, Washington Technical Information Division, ORDO University of California, Information Division Chemistry Department kitrersity of Rochester Office of.Chicago Directed Operations UCRL-I02 July 19, 1948 ELECT??@PICSTRUCTURE OF TITE HEAVIEST ELENElTTS FY O. T. Seaborg Tcblc of Contents I. Kistorical Rackground . r . 5 A'. Rcforo the Dfscoverg of thc Transuranium 7lcmcnts . .. 5 Re kftcr the Discovcrg of thc Transurnnium r';lcmcnts. 8 11. ~ctinLdcConcrpt . 9 A,. Goncral.. 9 R. Chemical vidcncc . 10 C'. Absorption Spcctra in Aqucous Solution and Crystals . 18 n-b Cr$stallogrc~l~icTE-t:! . r . 20 E; Mc%nctic Susccptibf lity Datz . 22 Pa Spootroocopic Data . 24 111. Correlations and Deductions . 25 A. Electronic Configurations . 25 3. Possible Deductions without Data on Transuranium 7i;llerncnts . 28 C. Position in Fcrioclic Tnblc 2nd Nomcnclaturc . 29 Dm Prc?dictcd! Properties of Transcurium xlcmcnt s . 31 Refcrcnccs . 33 Page 4 ELECTRONIC STRUC TITBE Or! TTTE HEAYLEST EX:Z.?TFTS By Glenn T. Seaborg Abstract-- All of the available evidence leads to the view that the 5f electron shell i.s bein: filled in the heaviest elements givin,? rise to a transition series which begins with actinium in the same sense that the rare earth or 1' lanthanide tt series begins a-ith lanthanum. Such ar? 1' actini6e 11 series is suggested on the basis of evidence in the following lines: (1) chemical pro?erties, (2) absorption spectra in aqueous solution and crystals, (3) cry- ~tallo~zraphicstructure data, (4) rnaenetf c sus ceptibilitg data and (5) spectroscopic data, The salient point is that the charac- teristic &idation state (i.e ., the oxidation state exhibited by the member cont;ainin& seven 5f and presumably also by the mom- ber coztaining fourteen 5f electrons, curium and element 103) is the 111 state, and the group is placed in the priodic table on this basis, The data also make it possible to ~ivea suggested table of electronic configurations of the ground state of the gaseous atom for each of the elements from actinium to curium inclus ive . UC7L-102 July 19, 1945 Page 5 ELECTROFIC STRTC TUPE 0" TV4: FZAVIEST ELEPIEKC S By Glenn T. Seaborg I. Historical Eackground P,. Before the Discovery of the Transuranium xlements. The intensive study of the heavy elements during the last few years has given information and data which now enable us to make some definite statements as to their electronic structure. The fnfor- mation obtained about the recently discovered synthetic trans- uranium elements has been particularly useful in this connection, and it is largely on the basis of these new elements that this question is now well understood. The neaviest natural elements, thorium, protactinium and uranium, of atomic numbers 90, 91 and 92, respectively, lie in corresponding positions just below the 6th period 11 trans it ion ft elements, hafnium, tantalum and tunzsten, in which the 5d elec- tron shell i s being filled. The elements, hafnium, tantalum and tungsten are similar in their chemical properties to the correspond- ing transition elements in the 5th period., zirconium, columbium, and molybdenum, in which the 4d shell is beins filled. It has long been known that the chemical properties of thorium, protactinium and uranium resemble those of these 4d and 5d elements and for this reason most of the textbooks and standard works on chemistry and physics in which the electron stru-cture is discussed have accepted the view that it is the 6d shell which is being filled. Thus the structure of the elements above radon (element P 86) through uranium is written to show the addition of the next two electrons in the 7s shell tor element 87 (francium) an6 element UC9L-102 Page 6 # 88 (radium) and addition in the 6d shell for tho following four rr*l . elements, actinium, thorium, protactinium and uranium (1). Many of the early papers which appeared after Y. Rohrts clas- sical work(') on the qantj-zer? n~clearatm: discuss the electronic structure of the heaviest elements. Therc has bcen general agree- ment that some type of transition group should begin in the neighborliood of the se e lernent s, although there has been difference of opinion as to %here it begins and as to which electron shells are involvsc7. A nuinbor of the earliest publications even have aug.;ested that this transition series involves the filling of the 5f shell, thus possibly giving rise to a rare earth" group in a manner analogous to the filling of the 4f shell. This filling of thc: 4f shell rcsults in the well known grou~of 14 rare earth elements of atomic numbers 53-71 inclusive, following lanthanum. It is of interest here to note 2 few of thcse early and also latep suggestions in order to rovicw thc general. previous status of this question. Most of these emly investigators were of tho opinion that the filling of the 5f shell should begin at some point beyond uranium, that is, beyond the then known e lem~nts. In an early paper Bohr (3) suigested that the addition of the 5f electrons might begin in this region, and in a Rolir-Thomsen type of periodic table he pictured the first entry at the element with atomic number 94, Y. Suguira and He C. ~ro~(~)gave calcula- tions Indicating that the first entry of the electron into th~ 5f shell should occur at element 95, J. C, McL~nnan, A. R. McLag ad Y. F, Smith ()suggested as an alternative to the fill- ing of the 6d shell the possibility that thr 5f shell begins to be occupied in thorium. In a review article, S. Dushman (6) stated it is doubtful that the added electrons enter the 6d le vel (thus k* implying an analosg with. cerium, etc.). V. Karapetoff and 0 Ta-You-Wu and S. ~ouc?smit(') suggested that thc element with atomic number 93 might be the first in which the 5f shell besins to be filled, while A. von C-rossc(9) suggested, zs n possible a1- ternative to filling of the 6d shell, the entry of the first electron in the 5f shell with uranium. More recently L. L. Qurll (10), largely for the purpose of' illustration, presented periodic table arranccrncnts in vvhich thc first 5f electron appears in element number 95 in one case and in elenent nunbcr 99 in another. Tb later calculations of PI. C-oeppert yayPr(I1) ind-icate that the filling of the 5f shell might begin at protacthiurn or uranium. ,wid TZ. Rudy ( l2a) J. Prrr3.n(l2)/ on zemrsl conside~ationa, proposed as a possi- bility the theory that the first 5f electror, a;.;poars in thorium (13) and Ci. 7. Trillar suggested that some ot tho chemical evidence supports this viewpoint. On the basis of his crysta1logrs;~hicxork, V. M. Goldschfdt (14) favors the view that the first 5f electron entoys at protactinium, thc first element beyond thorium, although he points out thc pos- sibility that this mag occur either earlier, in thorium, or later, in uranium or in. the (at the time unlmowr?) transuranium clments. Ry analogy with the namc 11 IantharildeI' serLes which he had alrcadg proposed for the rare earth elements because these 14 clemnts followj-ng lanthanum have lanthanum as their prot otypc, he pro- posed the name " thoridc 11 scrios for the ld elornents folloxing kS thorium. On tho basts of his much morc complete crystallo~r~phic evidence, -including especially observations on thc t ransuranium F. After the I7iscovorg of the Transuranj.um---- -1ement- s. The ' C"* recent discovery of the 'translnanium elcmcnt s and thc study of 0 their properties, e speci~llgthe chcmical proprt fcs, have given us a tremendous amount of additional ovidcncc of just thc type needed to clarify this problem. AS it turns out, it is Ln the transuranium elements that thc really definitive chcmical pro- perties, from thc standpoint of olacing the heaviest cl-emnts in the >criodic table, first appear. Thc f trst bcst definite cvidcnce that the 5f shell undergoes filling in this hcavg region came from the trmcr chemical observations of 3. M. McMillan and P. He Abelson (I6)on element 93 (nontnnium); upon their discovery of this, thc first transuranium *-lemcnt, thcg nerc able to show definitely that it rrsembles uranium in its chemical properties and.