The Transactinide Elements

At present, some 36 isotopes of the transactinide elements have been characterized and these are summarized in Table 31.8. 

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. 

Figure 15.16 Adsorption enthalpies, AHa, on Si02 for Group 4 tetrachlorides and tetrabromides. [From K. E. Gregorich, In Radiochemistry of Rutherfordium and Hahnium, Proc. The Robert A. Welch Foundation. 41st Conference on Chemical Research—The Transactinide Elements, Houston, Texas, Oct. 27 - 28 (1997), p. 95.]...

The Transactinide Elements. Proceedings of the 41st Robert Welch Conference on Chemical Research, Welch, Houston, 1998. The best modern summary of many aspects of the study of the heaviest chemical elements. 

Gaggeler, H.W. Chemistry of the Transactinide Elements . In Proceedings of The Robert A. Welch Foundation Conference on Chemical Research XXXIV. Fifty Years with Transuranium Elements , Houston, Texas, 22-23 October 1990, pp. 255-276. 

Kratz, J.V. Chemical properties of the Transactinide Elements . In Heavy Elements and Related New Phenomena, Eds. Greiner, W., Gupta, R.K., World Scientific, Singapore, (1999) 129-193. 

J.F., Constantinescu, M., Barci, V., Weiss, B., Gasparo, J., Ardisson G. Extended abstracts. 1 St International Conference on the Chemistry and Physics of the Transactinide Elements, Seeheim, September 26-30 (1999). Contribution PW-20... 

Atoms of the transactinide elements are produced at extremely low rates atoms per minute for Rf and Db, down to atoms per day for elements 106-108. They are produced among much larger amounts of background activities which hinder the detection and identification of decay of the transactinide atoms of interest. For these reasons, there is a recognized need for a physical pre-separation of the transactinide element atoms before chemical separation. Thus, it has been proposed that a kinematic separator could be coupled to a transactinide chemistry system with an aerosol gas-jet device, and a workshop has been held to discuss the merits and design of such a device [33],... 

Liquid-phase chemical separation techniques have been used for over 100 years, thus their utility for separation and isolation of the chemical elements has been demonstrated. Adaptations of these well-understood separation techniques have been applied to the transactinide elements. These adaptations have been developed to overcome the single-atom and short half-life limitations inherent in the study of transactinide element chemical properties. 

With the advent of the use of kinematic pre-separators, as described in Section 2.2.2 above, the requirements of the chemical separation have been relaxed. It is no longer necessary to have the highest separation factors from interfering Bi, Po, and actinide radioactivities, so simpler separations which are more specific to the transactinide element being studied can be used. These relaxed separation requirements will allow development of simpler chemical separation techniques, and may lead to a new interest in manually performed chemical separations. 

This modular separation and detection system allows the use of well-understood liquid-liquid extraction separations on timescales of a few seconds, with detection efficiencies near 100%. This extremely fast chemical separation and detection system has been used with a sub-second a-active nuclide [67,68]. However, for the transactinide elements, which are produced in much lower yields with larger amounts of interfering 13-activities, detection of the a-decay of the transactinide isotopes failed. As described in Section 2.2.3, pre-separation with the Berkeley Gas-filled Separator before transport to and separation with SISAK allowed the chemical separation and detection of 4-s 257Rf [34], A schematic of the BGS-RTC-SISAK apparatus is presented in Figure 6. These proof-of-principle experiments have paved the way for detailed liquid-liquid extraction experiments on short-lived transactinide element isotopes. 

A renewed interest in studying the chemical properties of the transactinide elements in more detail both experimentally and theoretically arose in the late 1980s, see [18-26] for recent reviews. A series of manually performed separations of 261Rf in aqueous solutions was performed by the Berkeley group at the Berkeley 88-Inch Cyclotron [2-6,27], Their experiments involving liquid-liquid extractions typically comprised the following steps ... 

Tiirler, A. Gas Phase Chemistry of the Transactinide Elements Rutherfordium, Dubnium, and Seaborgium , in Habilitation Thesis, Bern University (1999). 

Diillmann, Ch.E., Tiirler, A., Eichler, B., Gaggeler, H.W. "Thermochromatographic Investigation of Ruthenium with Oxygen as Carrier Gas" In Extended Abstracts of "1st International Conference on Chemistry and Physics of the Transactinide Elements", Seeheim, Germany, 26-30 September 1999, P-M-13. 

Relativistic calculations allow more detailed predictions of the chemical properties of transactinides compared with those of their lighter homologues. Electi onic configurations and oxidation states predicted for the transactinide elements 104 to 120 on the basis of relativistic Hartree-Fock calculations are listed in Table 14.6. An important result of these calculations is the splitting of the p levels into a pi/2 sub-level for 2 electrons and a P3/2 sublevel for 4 electrons. 

M. Schadel, Chemistry of the Transactinide Elements, Radiochim. Acta 70/71, 207 (1995)... 

J. V. Kratz, Chemical Properties of the Transactinide Elements, in Heavy Elements and Related Phenomena (Eds. W. Greiner, R. K. Gupta), World Scientific, Singapore 1998, Vol. I. 

The Chemistry of the Heavier Transition Metals 587 Oxidation States and EMFs of Groups ]-12 588 The Lanthanide and Actinide Elements 599 Coordination Chemistry 608 The Transactinide Elements 613... 

---