Chemistry of the Transuranium Elements

Some have taken the viewpoint that, without the special stability associated with nuclear shell structure, elements as light as Z = 106-108 would have negligibly short half-lives. The mere existence of these nuclei with millisecond half-lives is said to be a demonstration that we have already made superheavy nuclei, according to this view. The shell stabilization of these nuclei, which are deformed, is due to the special stability of the N = 162 configuration in deformed nuclei. (The traditional superheavy nuclei with Z 114, N = 184 were calculated to have spherical shapes.) 

The chemical behavior of the transuranium elements is interesting because of its complexity and the insights offered into the chemistry of the lighter elements. The placing of these manmade elements into the periodic table (Fig. 15.1) represents one of the few significant alterations of the original periodic table of Mendelyeev. Since so little is known about the chemistry of the transactinide elements, one has the unique opportunity to test periodic table predictions of chemical behavior before the relevant experiments are done. 

The actinide and known transactinide elements are transition elements, that is, they have partially filled f or d electronic orbitals. As such, they are metals. Like other transition metals, most of them are sufficiently electropositive to dissolve in mineral acids. However, there is an important distinction that separates the actinide 

The ionic radii of the M3+ and M4+ ions of the actinides decrease with increasing positive charge of the nucleus (the actinide contraction) (Fig. 15.15). This contraction is due to the successive addition of electrons in an inner f shell where the incomplete screening of the nuclear charge by the added f electron leads to a contraction of the outer valence orbital. Because the ionic radii of ions of the same oxidation state are generally similar (Fig. 15.15), the ionic compounds of the actinides are isostructural. 

The comparable energies of the 5f, 6d, 7s, and 7p orbitals and their spatial overlap will lead to bonding involving any or all of them. Thus, complex formation is an important part of actinide chemistry. The most stable oxidation states of the actinides and their solution chemistry will depend on the ligands present also because of the small differences between the energy of the electronic levels relative to chemical bond energies. 

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E. M. McMillan and G. T. Seaborg (Berkeley) discoveries in the chemistry of the transuranium elements. 

Keller, C. "The Chemistry of the Transuranium Elements," Verlag Chemie GmbH, Weinheim/Bergstr., Germany, 1971, p. 229. 

A77. C. Keller, The Chemistry of the Transuranium Elements. Verlag Chemie, Weinheim, 1971. Chapter 8, Organometallic compounds of the actinides, pp. 187-193 (36). Not as comprehensive as reference 4.39. 

G. T. Seaborg and E. M. McMillan. The Nobel Prize for Chemistry for 1951 was awarded jointly to Glenn T. Seaborg and Edwin M. McMillan, both of the University of California, for their discoveries in the chemistry of the transuranium elements." Dr. Seaborg is chairman of the Division of Physical and Inorganic Chemistry at the University of California. Dr. McMillan worked at the Massachusetts Institute of Technology in connection with radar development, collaborated with J. Robert Oppenheimer in organizing the Los Alamos Scientific Laboratory, and did the initial work that led to the discovery of elements heavier than uranium. 

MCMILLAN, EDWIN M. (1907-1991). An American physicist who won the Nobel prize in chemistry in 1951 along with Glenn T. Seaborg lor their discoveries In the chemistry of the transuranium elements. His work included research in nuclear physics and particle accelerator development as well as microwave radar and sonar. He and his colleagues discovered neptunium and plutonium. He was the recipient of the Atoms for Peace prize in 1963. His Ph D. in Physics was awarded from Princeton University. 

Despite the extremely low concentrations of the transuranium elements in water, most of the environmental chemistry of these elements has been focused on their behavior in the aquatic environment. One notes that the neutrality of natural water (pH = 5-9) results in extensive hydrolysis of the highly charged ions except for Pu(V) and a very low solubility. In addition, natural waters contain organics as well as micro- and macroscopic concentrations of various inorganic species such as metals and anions that can compete with, complex, or react with the transuranium species. The final concentrations of the actinide elements in the environment are thus the result of a complex set of competing chemical reactions such as hydrolysis, complexation, redox reactions, and colloid formation. As a consequence, the aqueous environmental chemistry of the transuranium elements is significantly different from their ordinary solution chemistry in the laboratory. 

C. Keller, The Chemistry of the Transuranium Elements , Verlag Chemie, Weinheim, 1971, p. 414. 

In 1951 McMillan and Glenn T. Seaborg received the Nobel Prize in chemistry for their discoveries in the chemistry of the transuranium elements. He also received the 1950 Research Corporation Scientific Award and, in 1963, the Atoms for Peace Award along with Professor V. I. Veksler. He retired in 1973. 

D.C. Hoflinami and D.M. Lee (1999) Journal of Chemical Education, vol. 76, p. 331 - Chemistry of the heaviest elements - One atom at a time is an excellent article covering the development and future prospects of atom-at-a-time chemistry of the transuranium elements. 

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