Berkelium and Californium

A detailed study of the hydrolysis reactions of curium(III) has been undertaken by Fanghanel et al. (1994) in NaCl media and at 25 C using time-resolved laser fluorescence spectroscopy (TRLFS). This study provided data on the stabihty constants of CmOH + and Cm(OH)2 in 0.011-6.15molkg NaCl. The constants relate to reaction (2.7) (M = Cm , p=, q= oi2). The reported stabihty constants are listed in Table 9.26 and are given with respect to reaction (2.7). 

Morss and Wilhams (1994) also estimated the solubility constant data for Bk(OH)g(s) and Cf(OH)g(s) from thermodynamic data determined for americium hydroxide and the relative change across the solubility of the lanthanide hydroxide phases. The solubilities (log determined for the two phases were 13.5 2.0 and 13.0 2.0, respectively. These values are retained in the present study  

Desire, Hussonnois and GuUlaumont (1969) determined stability constants for the species AnOH + for the actinides, plutonium(III), americium(III), curium (III), berkelium(III) and californium (III) using a solvent extraction technique. The stability constants obtained for americium(III) and curium(III) are two orders of magnitude larger than other similar data available in the literature. The stability constants of the lanthanide(III) and actinide(III) ions are very difficult to obtain using solvent extraction due to problems associated with attainment of maximum extraction into the solvent phase before the narrow band of pH between the onset of hydrolysis reactions and the precipitation of solid hydroxide phases. Consequently, the data of Desire, Hussonnois and GuUlaumont (1969) are not retained in this review. 

Ahrland, S. (1949) On the complex chemistry of the uranyl ion. I. The hydrolysis of the six-valent uranium in aqueous solution. Acta Chem. Scand., 3, 374—400, 

Allard, B., Kipatsi, H., and Liljenzin, J.O. (1980) Expected species of uranium, neptunium and plutonium in neutral aqueous solutions. /. Inorg. Nucl. Chem, 42, 1015-1027. 

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Studier, P. R. Fields and J. R. Huizenga Berkelium and Californium Isotopes Produced in Neutron Irradiation of Plutonium. Phys. Rev. 96, 1576 (1954). 

These elements have all been named for famous scientists or for the places of their creation. For example, americium, berkelium, and californium were named after obvious geographical locations. Nobelium was named for the Nobel Institute, although later study proved it was not really created there. Curium was named for Marie Curie, the discoverer of radium. Einsteinium was named for the famous physicist, Albert Einstein. Fermium and lawrencium were named for Enrico Fermi and Ernest O. Lawrence, who made important discoveries in the field of radioactivity. Mendelevium was named for the discoverer of the periodic chart. 

The higher actinide metals americium, curium, berkelium and californium have - at normal pressure - again the common structure dhcp and are in this respect similar to some of the lanthanide metals. In fact, the theoretical calculations and certain experimental observations show that in these actinide metals, 5 f electrons are localized, as are the 4f electrons in the lanthanide metals. More detailed considerations on the possible correlations between electronic and crystal structure are found in. ... 

Then, curium metal is antiferromagnetic and its paramagnetic effective moment definitively supports the picture of a localized 5 f configuration the same is true for what is known about berkelium and californium metals ... 

In 1951 along with Edwin McMillan he received the Nobel prize in chemistry for the creation of the first transuranium elements. He created plutonium, americium, curium, berkelium, and californium at Berkeley. 

The references given in Table I are those describing the preparation of a given compound the reference may or may not contain information on the behavior of the compound with time Note that the compounds have been synthesized in different oxidation states and different crystal structures where possible Not shown in the table are einsteinium, berkelium, and californium phosphates which have also been prepared and are being studied at present (11) ... 

This collection of the state-of-the-art papers emphasizes the continuing importance of industrial-scale production, separation, and recovery of transplutonium elements. Americium (At. No. 95) and curium (At. No. 96) were first isolated in weighable amounts during and immediately after World War II. Berkelium and californium were isolated in 1958 and einsteinium in 1961. These five man-made elements, in each case, subsequently became available in increasing quantities. 

The elements with the atomic numbers 97 and 98 (berkelium and californium) at first could not be produced by irradiation with neutrons, because isotopes of Cm exhibiting jfi" transmutation were not known. After milligram amounts of " Am had been produced by reaction (14.14), was obtained in 1949 by Thompson, Ghiorso and others by irradiation with a particles ... 

Plutonium and the four heavier trans-uranium elements whose existence have been reported, americium, curium, berkelium, and californium, were discovered by Professor G. T. Seaborg and his collaborators at the University of California in Berkeley. Americium has been made as the isotope Am by the following reactions ... 

The use of cyclotron-accelerated a-particles provides another method of producing plutonium, curium, americium, berkelium and californium ... 

One reason that scientists often argue over the discovery of an element is this The group of scientists that discovers an element usually has the opportunity to suggest a name for it. For example, researchers at the Berkeley laboratory first discovered elements 97 and 98. They suggested naming those elements berkelium and californium, in honor of Berkeley, California, where the research was done. 

Plutonium and the next four transuranium elements —americium, curium, berkelium, and californium —were discovered by G. T. Seaborg and... 

Actinium and thorium have no / electrons and behave like transition metals with a body-centered cubic structure of thorium. Neptunium and plutonium have complex, low-symmetry, room-temperature crystal structures and exhibit multiple phase changes with increasing temperature due to their delocalized 5/ electrons. For plutonium metal, up to six crystalline modifications between room temperature and 915 K exist. The / electrons become localized for the heavier actinides. Americium, curium, berkelium, and californium all have room-temperature, double hexagonal, close-packed phases and high-temperature, face-centered cubic phases. Einsteinium, the heaviest actinide metal available in quantities sufficient for crystal structure studies on at least thin films, has a face-centered cubic structure as typical for a divalent metal. 

It is also useful to note that berkelium and californium can be readily separated by extracting Bk(iv) away from Cf(m). This separation is important since isotopically pure is obtained from the beta decay of Bk. The Bk(iv) can be generated by oxidizing Bk(m) with a strong oxidant (NaBr03) in nitric acid solution. 

Selected values of actinide aquo-ion enthalpies of formation of actinium through berkelium (except for any Pu(vii) species) were assessed by Fuger and Getting [15] their values have been adopted here in Tables 17.1 and 17.14. For berkelium and californium, new measurements have provided the tabulated enthalpies of formation. All An values are plotted in Fig. 17.1. For heavier actinides, Nugent et al. [29] estimated enthalpies of formation systematically David et al. [25,27] applied more elaborate systematics and electrochemical measurements to estimate aquo-ion enthalpies of formation. David s predictions for and AHf(Cf ) have been borne out by experiments. Some... 

The citrate ion was the eluting agent used in the first isolation of berkelium and californium [189,190]. Soon afterwards, however, the lactate and tartrate ions were found to give considerably improved separations between americium(iii) and curium (ill) [191]. Lactate elution also proved superior to the classic citrate elution for the first isolation of einsteinium and fermium [188]. Later on, an even more selective eluant for actinide(iii) ions has been found in the a-hydroxyisobutyrate ion [192], With this ligand, very clean separations of the heavy actinide(iii) ions can be achieved, as illustrated in Fig. 21.12. The first isolation of mendelevium was achieved by this procedure [193]. 

R. (1969) Determination of the first hydrolysis constant of americium, curium, berkelium and californium. C.R. Acad. Sci.,... 

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