Actinide elements abundance

Comparison of experimental and theoretical studies of the solution absorption and luminescence spectra of lanthanide and actinide ions is the focus of this chapter. In aqueous solutions, the most stable oxidation state of lanthanide ions is 3+, but actinide-ion formal oxidation states ranging from 2+ to 7 -I- are known (Seaborg and Loveland 1990). Actinide elements heavier than plutonium exhibit more lanthanidelike behavior, however, in that 3-1- is their most stable formal oxidation state in aqueous solution. The visible and near-infrared absorption spectra of trivalent lanthanide and actinide ions in solution provide such rich detail that the spectra may fairly be said to fingerprint the ion for identification. The abundance of sharp spectral features long confronted theoretical and experimental spectroscopists with difficult problems. The efforts of numerous workers have provided interpretation of many aspects of the spectra of these f-transition elements significant challenges remain. 

Uranium was the first actinide element to be discovered. M. H. Klaproth showed in 1789 that pitchblende contained a new element and named it uranium after the then newly discovered planet Uranus. Uranium is now known to comprise 2.1 ppm of the Earth s crust, which makes it about as abundant as arsenic or europium. It is widely distributed, with the principal sources being in Australia,... 

The toxic properties of plutonium have attracted interest to such an extent that it has become one of the best understood toxic substances known. Although plutonium has been known since 1940 and has been manufactured and handled on a large scale, no unquestionable direct relationship, 40 years later has been established between its toxicity and human death [65]. Everything known about the toxicity of plutonium has been learned from animal experimentation, as there is no known case of ingestion by a human of a suffidently large amount of plutonium to produce symptoms of acute toxicity. The application of information acquired in this way to humans can only be by extrapolation, which raises questions of species specificity that cannot be answered at this time. The information available about the other actinide elements is fragmentary and much less abundant, and generalizations must be accepted with reservations. 

The actual situation with regard to the purity of most of the actinide metals is far from ideal. Only thorixun (99), uranium 11,17), neptunium 20), and plutonium 60) have been produced at a purity > 99.9 at %. Due to the many grams required for preparation and for accurate analysis, it is probable that these abundant and relatively inexpensive elements (Table I) are the only ones whose metals can be prepared and refined to give such high purities, and whose purity can be verified by accurate analysis. The purity levels achieved for some of the actinide metals are listed in Table II. For actinium (Ac), berkelium (Bk), californium (Cf),... 

Figure 12.4 Vertical profiles of the Group 3 elements in the North Pacific Ocean, including selected actinides. Data sources Sc (Spencer et al., 1970), Y, La, Pr-Lu (Zhang and Nozaki, 1996), Ce (Piepgras and Jacobsen, 1992), Ac (Nozaki, 19 84), 232Th (Roy-Barman et al., 1996), U (Chen et al., 1986) and 241Am (Livingston et al., 1983). Relative species abundance is shown to the right of each figure in descending order.

The lanthanides (Ln) include lanthanum (La) and the following fourteen elements—Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu— in which the 4f orbitals are progressively filled. These fifteen elements together with scandium (Sc) and yttrium (Y) are termed the rare-earth metals. The designation of rare earths arises from the fact that these elements were first found in rare minerals and were isolated as oxides (called earths in the early literature). In fact, their occurrence in nature is quite abundant, especially in China, as reserves have been estimated to exceed 84 x 106 tons. In a broader sense, even the actinides (the 5f elements) are sometimes included in the rare-earth family. 

Corrected on the first ionization potential, the elemental composition at cosmic ray sources as compared to the solar and local galactic composition exhibits the underabundance of H and He by a factor of 10 (if normalized to Fe). It also demonstrates higher Pt/Pb ratio by a factor of 5 and higher actinides abundance, the ratio (Z > 88)/(74 < Z < 87) by a factor of 3. These anomalies may be an indication that cosmic rays arise from supernova material (synthesized in the r-process) mixed with the interstellar gas. 

Related topics Actinium and the actinides (12) Origin and abundance of the elements (J1)... 

The actinides (U, Th, Pu), alkaline earths (Be, Mg, Ca, Sr, Ba), lanthanides (elements La - Lu), Al, and the elements in groups 3b (Sc, Y), 4b (Ti, Zr, Hf), and 5b (V, Nb, Ta) of the periodic table are refractory lithophile elements. The refractory lithophiles are 5% of the total mass of the rock in solar composition material. Aluminum Al, calcium Ca, and titanium Ti are the three most abundant refractory lithophiles, and they form minerals that are the host phases for most of the less abundant refractory lithophile elements such as the actinides, lanthanides, and transition elements in group 5b of the periodic table. Some of the less abundant refractory lithophiles - the group 4b elements Zr, Hf, and the group 3b elements Y and Sc - condense as oxides before any Ca, Al, Ti-bearing minerals form [9], But the rest condense into the more abundant host phases. 

Nuclear reaction(s) producing noble gas isotope(s) from stable or long-lived isotope during an irradiation in a nuclear reactor, or parent isotopes with half-lives less than 10 years, typical or suspected abundance at the time of formation of the solar system. For longer-lived parent isotopes, current abundance (%) of element. For actinides, " He yields are the number of atoms produced per decay chain, fission Xe yields are branching ratio for Xe. Yields for other isotopes are given in Table 2. 

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