Discovery of the Transuranium Elements, Table

▪ Table

Table 27: Discovery of the Transuranium Elements

atomic

number element symbol atomic 

weight   discoverers and 

date of discovery source of first 

preparation (half-life) first isolation in weighable 

amount (half-life)

93 neptunium Np 237*† E.M. McMillan and P.H. Abelson 

  at the University of California, 

  Berkeley, 1940 irradiation of uranium with neutrons 

  ²³⁸₉₂U + ¹₀n ——> ²³⁹₉₂U + gamma ray 

                 _ß- 

  ²³⁹₉₂U ——> ²³⁹₉₃Np (2.36 days)  1944, ²³⁷₉₃Np (2,140,000 years) 

  L.B. Magnusson and T.J. 

  La Chappelle at the 

  University of Chicago

94 plutonium Pu 239† 

244* G.T. Seaborg, E.M. McMillan, 

  J.W. Kennedy, and A.C. Wahl 

  at the University of California, 

  Berkeley, 1940 bombardment of uranium with deuterons 

  ²³⁸₉₂U + ²₁H ——> ²³⁸₉₃Np + 2¹₀n 

                    _ß- 

  ²³⁸₉₃Np  ——> ²³⁸₉₄Pu (87.7 years) 1942, ²³⁹₉₄Pu (24,100 years) 

  B.B. Cunningham and 

  L.B. Werner at the 

  University of Chicago

95 americium Am 241† 

243* G.T. Seaborg, R.A. James, L.O. 

  Morgan, and A. Ghiorso at 

  the University of Chicago, 1944–45 irradiation of plutonium with neutrons 

  ²³⁹₉₄Pu + ¹₀n ——> ²⁴⁰₉₄Pu + gamma ray 

  ²⁴⁰₉₄Pu + ¹₀n ——> ²⁴¹₉₄Pu + gamma ray 

                  _ß- 

  ²⁴¹₉₄Pu ——>   ²⁴¹₉₅Am (432 years) 1945, ²⁴¹₉₅Am (432 years) 

  B.B. Cunningham at the 

  University of Chicago

96 curium Cm 244† 

247* G.T. Seaborg, R.A. James, and 

  A. Ghiorso at the University 

  of Chicago, 1944 bombardment of plutonium with helium ions 

  ²³⁹₉₄Pu + ⁴₂He ——> ²⁴²₉₆Cm (163 days) + ¹₀n 1947, ²⁴²₉₆Cm (163 days) 

  L.B. Werner and 

  I. Perlman at the 

  University of California, 

  Berkeley

97 berkelium Bk 247* 

249† S.G. Thompson, A. Ghiorso, and 

  G.T. Seaborg at the University 

  of California, Berkeley, 1949 bombardment of americium with helium ions 

  ²⁴¹₉₅Am + ⁴₂He —> ²⁴³₉₇Bk (4.5 hours) + 2¹₀n 1958, ²⁴⁹₉₇Bk (320 days) 

  S.G. Thompson and B.B. 

  Cunningham at the 

  University of California, 

  Berkeley

98 californium Cf 251* 

252† S.G. Thompson, K. Street, Jr., 

  A. Ghiorso, and G.T. Seaborg 

  at the University of California, 

  Berkeley, 1950 bombardment of curium with helium ions 

  ²⁴²₉₆Cm + ⁴₂He ——> ²⁴⁵₉₈Cf (45 min) + ¹₀n 1958, ^{249, 250, 251, 252}Cf 

  B.B. Cunningham and S.G. 

  Thompson at the 

  University of California,   

  Berkeley

99 einsteinium Es 253† 

252* scientists at the University of 

  California, Berkeley; Argonne 

  National Laboratory, Illinois; 

  and Los Alamos Scientific 

  Laboratory, New Mexico; 1952 found in the debris from the first thermonuclear 

  explosion, nicknamed "Mike," engineered by 

  the Los Alamos Scientific Laboratory, New Mexico, 

  on Nov. 1, 1952, at Enewetak atoll, Marshall 

  Islands; successive neutron captures by uranium-238 

  and the subsequent ß^- decay of the capture products 

  resulted in ²⁵³₉₉Es (20.5 days) 1961, ²⁵³₉₉Es (20.5 days) 

  B.B. Cunningham, J.C. 

  Wallmann, L. Phillips, 

  and R.C. Gatti at the 

  University of California, 

  Berkeley

100 fermium Fm 257*† scientists at the University of 

  California, Berkeley; Argonne 

  National Laboratory, Illinois; 

  and Los Alamos Scientific 

  Laboratory, New Mexico; 1953 found in the debris from the first thermonuclear 

  explosion, nicknamed "Mike," engineered by 

  the Los Alamos Scientific Laboratory, New Mexico, 

  on Nov. 1, 1952, at Enewetak atoll, Marshall 

  Islands; successive neutron captures by uranium-238 

  and the subsequent ß^- decay of the capture products 

  resulted in ²⁵⁵₁₀₀Fm (20.1 hours) . . .

101 mendelevium Md 258* A. Ghiorso, B.G. Harvey, G.R. 

  Choppin, S.G. Thompson, and 

  G.T. Seaborg at the University 

  of California, Berkeley, 1955 bombardment of einsteinium with helium ions 

  ²⁵³₉₉Es + ⁴₂He ——> ²⁵⁶₁₀₁Md (1.3 hours) + ¹₀n . . .

102 nobelium No 259* A. Ghiorso, T. Sikkeland, 

  J.R. Walton, and G.T. Seaborg 

  at the University of California, 

  Berkeley, 1958   

      E.D. Donets, V.A. Schegolev, and 

  V.A. Ermakov at the Joint 

  Institute for Nuclear Research 

  at Dubna, Russia, 1964  bombardment of curium with carbon ions 

  ²⁴⁶₉₆Cm + ¹²₆C ——> ²⁵⁴₁₀₂No (55 sec) + 4¹₀n 

  (the isotope ²⁵²₁₀₂No was also produced and 

  incorrectly identified as ²⁵⁴₁₀₂No)  

bombardment of curium with carbon ions 

  ²⁴⁸₉₆Cm + ¹²₆C ——> ²⁵⁶₁₀₂No (3.3 sec) + 4¹₀n . . .  

       

. . .

103 lawrencium Lr 260* A. Ghiorso, T. Sikkeland, 

      

  A.E. Larsh, and R.M. Latimer 

  at the University of California, 

  Berkeley, 1961  

        

      E.D. Donets, V.A. Schegolev, and 

  V.A. Ermakov at the Joint 

  Institute for Nuclear Research 

  at Dubna, Russia, 1965

bombardment of a mixture of californium isotopes 

  with boron-10 ions and baron-11 ions 

  ²⁴⁹₉₈Cf                                           2¹₀n 

  ²⁵⁰₉₈Cf    +¹⁰₅B ——> ²⁵⁸₁₀₃Lr + 3¹₀n 

  ²⁵¹₉₈Cf    +¹¹₅B                             4¹₀n 

  ²⁵²₉₈Cf                                          5¹₀n 

  (the product was incorrectly identified as ²⁵⁷₁₀₃Lr in 

  1961; the isotope discovered was later proved to be 

  ²⁵⁸₁₀₃Lr; 3.9 sec) 

bombardment of americium with oxygen ions 

  ²⁴³₉₅Am + ¹⁸₈O ——> ²⁵⁶₁₀₃Lr (28 sec) + 5¹₀n . . . 

       

        

        

. . .

104 unnilquadium‡ 

rutherfordium** Unq 

Rf 261* A. Ghiorso, M. Nurmia, J. Harris, 

  K. Eskola, and P. Eskola at the 

  University of California, 

  Berkeley, 1969 

G.N. Flerov, Y.T. Oganessian, 

  Y.V. Lobanov, V.I. Kuznetsov, 

  V.A. Druin, V.P. Perelygin, 

  K.A. Gavrilov, S.P. Tretyakova, 

  and V.M. Plotko at the Joint 

  Institute for Nuclear Research 

  at Dubna, Russia, 1964  bombardment of californium with carbon ions 

  ²⁴⁹₉₈Cf + ¹²₆C ——> ²⁵⁷104 (4.7 sec) + 4¹₀n 

  ²⁴⁹₉₈Cf + ¹³₆C ——> ²⁵⁹104 (3.1 sec) + 3¹₀n  

bombardment of plutonium with neon ions 

  ²⁴²₉₄Pu + ²²₁₀Ne ——> ²⁶⁰104 + 4¹₀n 

  (identification of the isotope produced has not been 

  verified; later research has raised questions about some 

  of the assumptions on which the original discovery 

  claim was based)  . . . 

. . .

105 unnilpentium‡ 

hahnium 

dubnium** Unp 

Ha 

Db 262* A. Ghiorso, M. Nurmia, K. Eskola, 

  J. Harris, and P. Eskola at the 

  University of California, 

  Berkeley, 1970 

G.N. Flerov, V.A. Druin, 

  A.G. Demin, Y.V. Lobanov, 

  N.K. Skokelev, G.N. Akap'ev, 

  B.V. Fefilov, I.V. Kolesov, 

  K.A. Gavrilov, Y.P. Kharitonov, 

  and L.P. Chelnokov at the 

  Joint Institute for Nuclear 

  Research at Dubna, Russia, 1968  bombardment of californium with nitrogen ions 

  ²⁴⁹₉₈Cf + ¹⁵₇N ——> ²⁶⁰105 (1.5 sec) + 4¹₀n  

  

bombardment of americium with neon ions 

  ²⁴³₉₅Am + ²²₁₀Ne ——> ²⁶⁰105 + 5¹₀n 

  ²⁴³₉₅Am + ²²₁₀Ne ——> ²⁶¹105 + 4¹₀n 

  (the Dubna scientists reported observing alpha- 

  particle-emitting isotopes of element 105, but 

  their findings were generally considered inconclusive; 

  in 1970 Dubna scientists reported observing the nuclide 

  ²⁶¹105, which decayed by spontaneous fission)  . . . 

. . . 

106 unnilhexium‡ 

seaborgium** Unh 

Sg 266* A. Ghiorso, J.M. Nitschke, 

  J.R. Alonso, C.T. Alonso, 

  M. Nurmia, G.T. Seaborg, 

  E.K. Hulet, and R.W. Lougheed 

  at the University of California, 

  Berkeley, 1974 

Y.T. Oganessian, Y.P. Tretyakov, 

  A.S. Iljinov, A.G. Demin, 

  A.A. Pleve, S.P. Tretyakova, 

  V.M. Plotko, M.P. Ivanov, 

  N.A. Danilov, Y.S. Korotkin, 

  and G.N. Flerov at the Joint 

  Institute for Nuclear Research 

  at Dubna, Russia, 1974 bombardment of californium with oxygen ions 

  ²⁴⁹₉₈Cf + ¹⁸₈O ——> ²⁶³106 (0.8 sec) + 4¹₀n  

        

  

bombardment of lead with chromium ions 

  ²⁰⁷₈₂Pb + ⁵⁴₂₄Cr ——> ²⁵⁹106 + 2¹₀n 

  ²⁰⁸₈₂Pb + ⁵⁴₂₄Cr ——> ²⁵⁹106 + 3¹₀n 

  (later research showed that the observed spontaneous 

  fission was due to ^{256, 255}104, not element 106) 

. . . 

      . . .

107 unnilseptium‡ 

nielsbohrium 

bohrium** Uns 

Ns 

Bh 262* G. Münzenberg, S. Hofmann, 

  F.P. Hessberger, W. Reisdorf, 

  K.H. Schmidt, J.R.H. Schneider, 

  W.F.W. Schneider, P. Armbruster, 

  C.C. Sahm, and B. Thuma at the 

  Institute for Heavy Ion Research 

  at Darmstadt, Ger., 1981 bombardment of bismuth with chromium ions 

  ²⁰⁹₈₃Bi + ⁵⁴₂₄Cr ——> ²⁶²107 (0.1 sec) + ¹₀n . . .

108 unniloctium‡ 

hassium** Uno 

Hs 265* G. Münzenberg, P. Armbruster, 

  H. Folger, F.P. Hessberger, 

  S. Hofmann, J. Keller, 

  K. Poppensieker, W. Reisdorf, 

  K.H. Schmidt, H.J. Schött, 

  M.E. Leino, and R. Hingmann 

  at the Institute for Heavy Ion 

  Research at Darmstadt, Ger., 1984 bombardment of lead with iron ions 

  ²⁰⁸₈₂Pb + ⁵⁸₂₆Fe ——> ²⁶⁵108 (2 ms) + ¹₀n . . .

109 unnilennium‡ 

meitnerium** Une 

Mt 266* G. Münzenberg, P. Armbruster, 

  F.P. Hessberger, S. Hofmann, 

  K. Poppensieker, W. Reisdorf, 

  K. Schneider, K.H. Schmidt, 

  C.C. Sahm, and D. Vermeulen at 

  the Institute for Heavy Ion 

  Research at Darmstadt, 

  Ger., 1982  bombardment of bismuth with iron ions 

  ²⁰⁹₈₃Bi + ⁵⁸₂₆Fe ——> ²⁶⁶109 (3.4 ms) + ¹₀n . . .

110 ununnilium‡ Uun 271* S. Hofmann, V. Ninov, 

  F.P. Hessberger, P. Armbruster, 

  H. Folger, G. Münzenberg, 

  H.J. Schött, A.G. Popeko, 

  A.V. Yeremin, A.N. Andreyev, 

  S. Saro, R. Janik, and M. Leino 

  at the Institute for Heavy Ion 

  Research at Darmstadt, Ger., 1994 

A. Ghiorso, D. Lee, L.P. 

  Somerville, W. Loveland, 

  J.M. Nitschke, W. Ghiorso, 

  G.T. Seaborg, P. Wilmarth, 

  R. Leres, A. Wydler, M. Nurmia, 

  K. Gregorich, R. Gaylord, 

  T. Hamilton, N.J. Hannink, 

  D.C. Hoffman, C. Jarzynski, 

  C. Kacher, B. Kadkhodayan, 

  S. Kreek, M. Lane, A. Lyon, 

  M.A. McMahan, M. Neu, 

  T. Sikkeland, W.J. Swiatecki, 

  A. Türler, J.T. Walton, 

  and S. Yashita at the University 

  of California, Berkeley, 1991–94 

Y.A. Lazarev, Y.V. Lobanov, 

  Y.T. Oganessian, V.K. Utyonkov, 

  S. Iliev, V.G. Subbotin, 

  A.M. Sukhov, G.V. Buklanov, 

  B.N. Gikal, V.B. Kutner, 

  A.N. Mezentsev, K. Subotic, 

  I.F. Wild, R.W. Lougheed, 

  and K.J. Moody at the Joint 

  Institute for Nuclear Research 

  at Dubna, Russia, and Lawrence 

  Livermore National Laboratory, 

  California, 1994– bombardment of lead with nickel ions 

  ²⁰⁸₈₂Pb + ⁶²₂₈Ni ——> ²⁶⁹110 (0.17 ms) + ¹₀n 

  ²⁰⁸₈₂Pb + ⁶⁴₂₈Ni ——> ²⁷¹110 (1.4 ms) + ¹₀n  

        

       

      bombardment of bismuth with cobalt ions 

  ⁵⁹₂₇Co + ²⁰⁹₈₃Bi ——> ²⁶⁷110 (4 ms) + ¹₀n 

  (there is some evidence that one atom of ²⁶⁷110 may 

  have been created in 1991) 

        

       

      bombardment of plutonium with sulfur ions 

  ²⁴⁴₉₄Pu + ³⁴₁₆S ——> ²⁷³110 (0.3 ms) + 5¹₀n 

  (one decay chain attributable to ²⁷³110 has been 

  identified, but data is still being analyzed) . . . 

      . . . 

. . .

111 unununium‡ Uuu 272* S. Hofmann, V. Ninov, 

  F.P. Hessberger, P. Armbruster, 

  H. Folger, G. Münzenberg, 

  H.J. Schött, A.G. Popeko, 

  A.V. Yeremin, A.N. Andreyev, 

  S. Saro, R. Janik, and M. Leino 

  at the Institute for Heavy Ion 

  Research at Darmstadt, Ger., 1994 bombardment of bismuth with nickel ions 

  ²⁰⁹₈₃Bi + ⁶⁴₂₈Ni ——> ²⁷²111 (1.5 ms) + ¹₀n . . .

112 ununbium‡ Uub 277* S. Hofmann, V. Ninov, 

  F.P. Hessberger, P. Armbruster, 

  H. Folger, G. Münzenberg, 

  H.J. Schött, A.G. Popeko, 

  A.V. Yeremin, S. Saro, 

  R. Janik, and M. Leino at 

  the Institute for Heavy Ion 

  Research at Darmstadt, Ger., 1996 bombardment of lead with zinc ions 

  ²⁰⁸₈₂Pb + ⁷⁰₃₀Zn ——> ²⁷⁷112 (0.3 ms) + ¹₀n . . .

See as table:

      *Mass number of longest-lived isotope.   †Mass number of more available isotope.   ‡Temporary systematic name assigned by the International Union of Pure and Applied

Chemistry (IUPAC) until a permanent name has been approved.   Name recommended by the American Chemical Society Committee on Nomenclature in 1994.

**Name recommended by the IUPAC in 1997.

* * *