Chapter Ten Berkelium

As was the case for the previously discovered transuranium elements, element 97 was first produced via a nuclear bombardment reaction. In December 1949 ion‐exchange separation of the products formed by the bombardment of Am with accelerated alpha particles provided a new electron‐capture activity eluting just ahead of curium (Thompson et al., 1950a,b). This activity was assigned to an isotope (mass number 243) of element 97. The new element was named berkelium after Berkeley, California, USA, the city of its discovery, in a manner parallel to the naming of its lanthanide analog, terbium, after Ytterby, Sweden. The initial investigations of the chemical properties of berkelium were limited to tracer experiments (ion exchange and coprecipitation), and these were sufficient to establish the stability of Bk(III) and the accessibility of Bk(IV) in aqueous solution and to estimate the electrochemical potential of the Bk(IV)/Bk(III) couple (Thompson et al., 1950b,c). Because a complete study of the chemistry of an element is not possible by tracer methods alone, a program for long‐term neutron irradiation of about 8 g of Pu was initiated in 1952 in the Materials Testing Reactor (Arco, Idaho, USA) to provide macroquantities of berkelium (Cunningham, 1959). In 1958 about 0.6 mg of Bk was separated, purified, and used in experiments to determine the absorption spectrum of Bk(III) in aqueous solution and to measure the magnetic susceptibility of Bk(III) (Cunningham, 1959). No Bk(III) absorption was observed over the wavelength range 450–750 nm, but an upper limit of about 20 was set for the molar absorptivity of any 10.1 Historical 1444 10.2 Nuclear properties, availability, and applications 1445 10.3 Production 1448 10.4 Separation and purification 1448 10.5 Properties of free atoms and ions 1451 10.6 The metallic state 1457 10.7 Compounds 1462 10.8 Ions in solution 1472 10.9 Analytical chemistry 1483 10.10 Concluding remarks 1484 References 1486