PREPRINTS OF THE 1998 ANNUAL SCIENTIFIC MEETING 97 studying. Subsequently, there was a hiatus in studies of chemical properties until 1985 when my group at Berkeley decided to investigate the'chemical properties of Lr and Rf in more detail, and then to perform studies of Ha in aqueous solution. The major impetus for our interest was the predictions based on relativistic calculations that the electronic structures, and hence the chemical properties, of these elements might show significant deviations from their lighter homologues. In fact, it was postulated that the most stable oxidation state for Ha might be 3+ rather than 5+ like the lighter group 5 elements, tantalum and niobium. Since relativistic effects are predicted to increase as Z 2 the heaviest elements should be the best place to assess the influence of these effects on ionic radii, complexing ability, oxidation states and redox properties. By this time, some longer-lived isotopes had also been discovered which made chemical studies more feasible than in the 1970s. My group then began its investigations of the chemical properties of the heaviest elements in 1985 to explore the architecture of the periodic table at its furthest reaches and to compare their properties with those of their lighter homologues. Because of the short half-lives of these elements, they must be studied at the accelerator where they are oroduced. Charged-oarticle beams must be used since they cannot be produced by neutron capture at reactors and the use of radioactive heavy actinide targets is often necessary. The production rates are so small that chemistry is performed on an *atom-at-a-time" basis and a knowledge of the nuclear decay properties of the element being investigated is required in order to detect these atoms and identify them. Our detailed studies showed anomalous trends in the chemical properties of Rf and Ha which could not be simply extrapolated from those of their lighter homologues in groups 4 and 5, of the periodic table, thus highlighting the importance of obtaining additional information for comparison with theoretical predictions of relativistic effects. These results sparked a renaissance of interest in chemical studies and we hosted many international collaborations at the 88-Inch Cyclotron at Berkeley. These have continued and our group has also participated in experiments at the UNILAC accelerator at Darmstadt, Germany. To date, we have studied the gas and aqueous phase chemical properties of Rf, Ha, and Sg, even though their longest known half-lives are only 78 seconds, 35 seconds, and 10 to 30 seconds, respectively. We use computer-controlled automated systems as well as "manual" separations for studying both aqueous and gas-phase properties and have found that Rf and Ha sometimes behave more like their pseudo-homologues, thorium (IV) and protactinium (V) than their group 4 and 5 homologues. Recent results have shown that the most stable oxidation state of Sg in aqueous solution is 6+, and like its homologues molybdenum and tungsten, Sg forms neutral or artionic oxy- or oxyhalide-compounds. However, somewhat unexpectedly, this is unlike the behavior of its possible pseudo-homologue U(VI).. We are now planning to try to produce a new isotope of Bh (element 107), predicted to have a half-life of-10 seconds, in order to study its chemistry. Based on new predictions of nuclear properties, it now appears that the half-lix•es of isotopes of elements 108 and 109, and even heavier, may be long enough for chemical studies but the production rates are dropping very rapidly. Now the trick will be to devise new and imaginative ways to increase the number of atoms produced in order to extend our studies of chemical properties to these elements..