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THE DISCOVERY OF THE TRANSURANIUM ELEMENTS: THEIR HISTORY AND A PRESENTATION OF THE DIFFERENT METHODS USED IN THEIR DISCOVERY

Description: BS>The ten transuranium elements discovered since 1940 are discussed in chronological order. The discoverer, the history, and methods used are given for each element. Future developments in the discovery and preparation of transuranic elements are discussed. (A.C.)
Date: April 1, 1959
Creator: Thompson, S.G.
Partner: UNT Libraries Government Documents Department

[Land Sale Document]

Description: Document selling 150 acres of land held by Ziza Moore to Elizabeth, M. B., and Nancy E. Damron. According to the agreement, the Damron family will pay $2,000 for the land in installments, including interest. The document is signed by Ziza Moore and two witnesses.
Date: September 11, 1866
Creator: Bedford County (Tenn.)
Partner: UNT Libraries Special Collections

THE NEW ELEMENT BERKELIUM (ATOMIC NUMBER 97)

Description: An isotope of the element with atomic number 97 has been discovered as a product of the helium-ion bombardment of americium. This isotope decays with the emission of alpha-particles of maximum energy 6.72 Mev (30 percent) and it emits lower energy alpha-particles of energies 6.55 Mev (53 percent) and 6.20 Mev (17 percent). The half-life of this isotope is 4.6 hours and it decays primarily by electron capture with about 0.1 percent branching decay by alpha-particle emission. The mass number is probably 243 as indicated by chemical separation of the alpha-particle and electron-capture daughters. The name berkelium, symbol Bk, is proposed for element 97. The chemical separation of element 97 from the target material and other reaction products was made by combinations of precipitation and ion exchange adsorption methods making use of its anticipated (III) and (IV) oxidation states and its position as a member of the actinide transition series. The distinctive chemical properties made use of in its separation and the equally distinctive decay properties of the particular isotope constitute the principal evidence for the new element.
Date: April 26, 1950
Creator: Thompson, S.G.; Ghiorso, A. & Seaborg, G.T.
Partner: UNT Libraries Government Documents Department

ELEMENT 98

Description: Definite identification has been made of an isotope of the element with atomic number 98 through the irradiation of Cm{sup 242} with 35 Mev helium ions in the Berkeley Orocker Laboratory 60-inch cyclotron. The isotope which has been identified has an observed half-life of about 45 minutes and probably has the mass number 244. The observed mode of decay of the 98{sup 244} is through the emission of alpha-particles, with energy about 7.1 Mev, which agrees with predictions, and other considerations involving the systematics of radioactivity in this region indicate that it should also be unstable toward decay by electron-capture. The chemical separation and identification of the new element was accomplished through the use of ion exchange adsorption methods employing the resin Dowex-50. The element 98 isotope appears in the eka-dysprosium position on elution curves containing 4.6-hour Bk{sup 243} (formed by a d,n reaction in the same bombardment) and the bombarded Cm{sup 242} as reference points; that is, it preceded berkelium and curium off the column just as dysprosium precedes terbium and gadolinium. The experiments so far have revealed only the tripositive oxidation state of eka-dysprosium character but practically no attempts at oxidation to possible IV and V states have been made as yet.
Date: February 27, 1950
Creator: Thompson, S.G.; Street, K.,Jr.; Ghiorso, A. & Seaborg, G.T.
Partner: UNT Libraries Government Documents Department

THE NEW ELEMENT CALIFORNIUM (ATOMIC NUMBER 98)

Description: Definite identification has been made of an isotope of the element with atomic number 98 through the irradiation of Cm{sup 242} with about 35-Mev helium ions in the Berkeley Crocker Laboratory 60-inch cyclotron. The isotope which has been identified has an observed half-life of about 45 minutes and is thought to have the mass number 244. The observed mode of decay of 98{sup 244} is through the emission of alpha-particles, with energy of about 7.1 Mev, which agrees with predictions. Other considerations involving the systematics of radioactivity in this region indicate that it should also be unstable toward decay by electron capture. The chemical separation and identification of the new element was accomplished through the use of ion exchange adsorption methods employing the resin Dowex-50. The element 98 isotope appears in the eka-dysprosium position on elution curves containing berkelium and curium as reference points--that is, it precedes berkelium and curium off the column in like manner that dysprosium precedes terbium and gadolinium. The experiments so far have revealed only the tripositive oxidation state of eka-dysprosium character and suggest either that higher oxidation states are not stable in aqueous solutions or that the rates of oxidation are slow. The successful identification of so small an amount of an isotope of element 98 was possible only through having made accurate predictions of the chemical and radioactive properties.
Date: June 19, 1950
Creator: Thompson, S.G.; Street, K.,Jr.; Ghiorso, A. & Seaborg, G.T.
Partner: UNT Libraries Government Documents Department

Alpha-Decay in Isotopes of Atomic Number Less Than 83

Description: Some time ago we started work in an attempt to observe alpha-particle decay in isotopes of atomic number less than 83. In the first experiments, thin targets of gold leaf were bombarded with 190-Mev deuterons in the 184-inch cyclotron. Two alpha-decay periods were observed in these targets; one of 0.7 minutes half-life and another of 4.3 minutes half-life. The alpha-particle energies were 5.7 and 5.2 Mev, respectively. Chemical separations proved that the 4.3-minute period is due to a gold isotope and suggested that the 0.7-minute period is due to a mercury isotope. The mass numbers of these new isotopes have not been determined. However, the results of excitation-functions in the production of the gold isotope by bombarding gold and platinum with protons suggest that its mass number lies in the range 185-188. The work on this isotope indicates that the alpha to electron capture branching ratio is of the order of magnitude of 10{sup -4}, and that positron activity accompanies the 4.3-minute alpha-period.
Date: September 5, 1949
Creator: Thompson, S.G.; Ghiorso, A.; Radmussen, J.O. & Seaborg, G.T.
Partner: UNT Libraries Government Documents Department

CALIFORNIUM ISOTOPES FROM BOMBARDMENT OF URANIUM WITH CARBONIONS

Description: The recent production and identification of isotopes of elements with atomic numbers up to six higher than the target element through bombardment with hexapositive 120-Mev carbon ions made it seem worthwhile to apply this technique to the transuranium region. Accordingly, small pieces of natural uranium metal (about 0.5 mil thick and 205 cm by 0.6 cm area) were irradiated in the internal carbon ion beam in the Berkeley 60-inch cyclotron. Following the irradiations, the uranium was dissolved in dilute hydrochloric acid containing hydrogen peroxide and a transplutonium fraction was isolated through the use of lanthanum fluoride, and lanthanum hydroxide precipitation steps followed by the ion exchange adsorption column procedure in which concentrated hydrochloric acid is used to separate the tripositive actinide elements from the rare earth elements. The transplutonium fractions in hydrochloric acid were evaporated as weightless films on platinum plates which were placed in the ionization chamber of the 48 channel pulse analyzer apparatus in order to measure the yield and energies of any alpha-particles which might be present. In the best experiment at about one hour after the end of the 90-minute bombardment, some 50 disintegrations per minute of the distinctive 7.1-Mev alpha-particles of Cf{sup 244} were observed to be present and to decay with the 45-minute half-life. The Cf{sup 244} was presumably formed by the reaction U{sup 238}(C{sup 12},6n). After the decay of the alpha-particles due to Cf{sup 244}, about five disintegrations per minute of alpha-particles with 6.8-Mev energy was observed and this alpha-radioactivity decayed with a half-life of about 35 hours. A consideration of the systematics of alpha-radioactivity leads us to the view that this activity is due to the new isotope Cf{sup 246} formed by the reaction U{sup 238}(C{sup 12},4n) . The measured half-life agrees with the expected alpha half-life for the observed energy for ...
Date: September 6, 1950
Creator: Ghiorso, A.; Thompson, S.G.; Street, K. Jr. & Seaborg, G.T.
Partner: UNT Libraries Government Documents Department

The New ELement Mendelevium, Atomic Number 101

Description: We have produced and chemically identified for the first time a few atoms of the element with atomic number 101. Very intense helium ion bombardments of tiny targets of 99{sup 253} have produced a few spontaneously fissionable atoms which elute in the eka-thulium position on a cation resin column.
Date: April 4, 1955
Creator: Ghiorso, A.; Harvey, B.G.; Choppin, G.R.; Thompson, S.G. & Seaborg, G.T.
Partner: UNT Libraries Government Documents Department

Chemical Properties of Elements 99 and 100

Description: A description of some of the chemical properties and of the methods used in the separations of elements 99 and 100 is given. The new elements exhibit the properties expected for the tenth and eleventh actinide elements. Attempts to produce an oxidation state greater than 111 of element 99 have been successful. In normal aqueous media only the 111 state of element 100 appears to exist. The relative spacings of the elution peaks of the new elements in some separations with ion exchange resin columns are the same as the relative spacings of the homologous lanthanide elements. The results of experiments involving cation exchange resins with very concentrated hydrochloric acid eluant show that the new elements, like the earlier actinides, are more strongly complexed than the lanthanides. The new elements also exist partially as anions in concentrated hydrochloric acid, as do earlier actinide elements, and they may be partially separated from each other by means of ion exchange resins. With some eluants interesting reversals of elution positions are observed in the region Bk-Cf-99-100, indicating complex ion formation involving unusual factors.
Date: July 23, 1954
Creator: Thompson, S.G.; Harvey, B.G.; Choppin, G.R. & Seaborg, G.T.
Partner: UNT Libraries Government Documents Department