Actinide atoms, reactions

Visible chemiluminescence has been observed from many reactions of lanthanide and actinide atoms producing metal oxides (M + N02, N20 and 03 [212]), but, in most cases, the spectra are unanalysed and it is not clear even what product MO states are produced. The variation of chemiluminescence intensity with reagent energy has been studied for the reactions Sm, Ho + N20. For Ho + N20, three excited electronic states are produced the relative population of the states decreasing as the energy of the states increases. There is no significant difference in... 

A further group of elements, the transuranium elements, has been synthesized by artificial nuclear reactions in the period from 1940 onwards their relation to the periodic table is discussed fully in Chapter 31 and need not be repeated here. Perhaps even more striking today are the predictions, as yet unverified, for the properties of the currently non-existent superheavy elements.Elements up to lawrencium (Z = 103) are actinides (5f) and the 6d transition series starts with element 104. So far only elements 104-112 have been synthesized, ) and, because there is as yet no agreement on trivial names for some of these elements (see pp. 1280-1), they are here referred to by their atomic numbers. A systematic naming scheme was approved by lUPAC in 1977 but is not widely used by researchers in the field. It involves the use of three-letter symbols derived directly from the atomic number by using the... 

The other actinides have been synthesized in the laboratory by nuclear reactions. Their stability decreases rapidly with increasing atomic number. The longest lived isotope of nobelium (102N0) has a half-life of about 3 minutes that is, in 3 minutes half of the sample decomposes. Nobelium and the preceding element, mendelevium (ioiMd), were identified in samples containing one to three atoms of No or Md. 

The existence of MBj, MB, MB,2 and MB borides depends on the metal atom size (see 6.7.2.4.6.). The di-, dodeca- and hectoborides are known only for the smaller lanthanides and actinides, and the hexaborides are known only for the larger members of each series. Thus high T (1100-1250°C) and pressures (65 X 10 N m ) are used to prepare SmB2, GdB,2 and ThB,2, phases unobtainable as products of the reactions carried out at high T only. ... 

As already noted, the carbonylation of bis(pentamethyl-cyclopentadienyl) actinide hydrocarbyls is irreversible in the cases studied thus far. Thus, thermolysis does not result in CO loss, but rather in interesting chemical reactions. Thermolysis of 1 ( 5) in toluene solution results in hydrogen atom migration to yield an enolate (eq.(5)). NMR studies establish that eq.(5) is essentially quantitative, and that the stereochemical course... 

In the review by Kanatzidis et al. (2005), the preparation by the tin-flux method is mentioned also for several ternary phosphides and polyphosphides of rare-earth and transition metals. Typically the components (R metal, T metal, P and Sn in an atomic ratio of about 1 4 20 50) in sealed silica tubes were slowly heated, to avoid violent reactions, up to 800°C, annealed at that temperature for 1 week and slowly (2 K/h) cooled to ambient temperature. The tin-rich matrix was dissolved in diluted hydrochloric acid. The authors described the preparation of compounds corresponding for instance to the formula MeT4P12 (Me = heavy rare-earth metals and Th and U, T = Fe, Ru, etc.) and to the series of phases MeT2P2 (Me is a lanthanide or an actinide and T a late transition metal) having a structure related to the BaAl4 or ThCr2Si2 types. 

Americium - the atomic number is 95 and the chemical symbol is Am. The name derives from America where it was first synthesized in a series of successive neutron capture reactions in the element plutonium, Pu, in a nuclear reactor in 1944 by American scientists under Glenn T. Seaborg at the University of California lab in Berkeley, California, using the nuclear reaction Pu ( n, y) Y) P Am. Americium is the sixth element in the Actinide... 

Often the products of nuclear reactions have very short half-lives. This is especially true for the heaviest elements obtained by bombardment of heavy targets with heavy ions. To identify and characterize such short-lived nuclides, fast separations are required solvent extraction techniques are well suited to provide the required fast separations. For example, the SISAK method [68] has been successfully used in conjunction with in-line gas jet separators at heavy ion accelerators to identify short half-life actinide isotopes produced by collision of heavy atoms. The Sisak method involves use of centrifugal contactors, with phase residence times as low as tenths of a second, in conjunction with in-line radiometric detection equipment. 

Dr. Darleane C. Hoffman of the Nuclear Science Division of the Lawrence Berkeley National Laboratory and Department of Chemistry at the University of California at Berkeley has written and presented several papers documenting her work and that of her team on the laboratory production of transactinide and actinide elements one-atom-at-a-time. She explains the difficulty of determining the chemistry of heavy elements How long does an atom need to exist before it s possible to do any meaningful chemistry on it Is it possible to learn anything at all about the reactions of an element for which no more... 

Atomic volume, of actinide metals, 31 36 Atom-transfer reactions, osmium, 37 340-... 

Actinides, the chemical elements with atomic numbers ranging from 89 to 103, form the heaviest complete series in the Periodic Table. They are radioelements, either naturally occurring or synthesized by nuclear reactions. Their predominant practical application depends on the nuclear properties of their isotopes decay, spontaneous or induced fission. Their chemical and physical properties reflect a very complex electronic structure, and their study and understanding are a challenge to experimentalists and theoreticians. 

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