Science - Encyclopedia Of Physical Science And Technology - Inorganic Chemistry -...
(Parte 1 de 13)
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Table of Contents (Subject Area: Inorganic Chemistry)
Article Authors Pages in the Encyclopedia
Actinide Elements Siegfried Hübener Pages 211-236
Bioinorganic Chemistry Brian T. Farrer and Vincent L. Pecoraro Pages 117-139
Boron Hydrides Herbert Beall and Donald F. Gaines Pages 301-316 Coordination
Compounds R. D. Gillard Pages 739-760
|Electron Transfer Reactions Gilbert P. Haight, Jr||Pages 347-361|
Dielectric Gases L. G. Christophorou and S. J. Dale Pages 357-371 Halogen Chemistry Marianna Anderson Busch Pages 197-2
Compounds Jerry L. Atwood Pages 717-729 Inorganic Exotic
Joel F. Liebman, Kay Severin and Thomas M. Klapötke Pages 817-838
Liquid Alkali Metals C. C. Addison Pages 661-671
Elements Russell L. Rasmussen, Joseph G. Morse and Karen W. Morse Pages 1-30
Materials, Synthesis Robert Mokaya Pages 369-381 Metal Cluster
Chemistry D. F. Shriver Pages 407-409
Metal Hydrides Holger Kohlmann Pages 441-458
Metal Particles and
Cluster Compounds Allan W. Olsen and Kenneth J. Klabunde Pages 513-550
Nano sized Inorganic Clusters Leroy Cronin, Achim Müller and Dieter Fenske Pages 303-317
(Chemistry) Hubert Schmidbaur and John L. Cihonski Pages 463-492
Noble-Gas Chemistry Gary J. Schrobilgen Pages 449-461
Periodic Table (Chemistry) N. D. Epiotis and D. K. Henze Pages 671-695
Rare Earth Elements and Materials Zhiping Zheng and John E. Greedan Pages 1-2
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Siegfried Hubener Forschungszentrum Rossendorf
I. Discovery, Occurrence, and Synthesis of the Actinides
I. Radioactivity and Nuclear Reactions of Actinides I. Applications of Actinides IV. Actinide Metals V. Actinide Ions VI. Actinide Compounds and Complexes
Actinyl ion Dioxo actinide cations MO+2 and MO2+ 2 .
Decay chain A series of nuclides in which each member transforms into the next through nuclear decay until a stable nuclide has been formed.
Lanthanides Fourteen elements with atomic numbers 58 (cerium) to 71 (lutetium) that are a result of filling the 4 f orbitals with electrons.
Nuclear fission The division of a nucleus into two or more parts, usually accompanied by the emission of neutrons and γ radiation.
Nuclide Aspeciesofatomcharacterizedbyitsmassnumber, atomic number, and nuclear energy state. A radionuclide is a radioactive nuclide.
Primordial radionuclides Nuclides which were produced during element evolution and which have partly survived since then due to their long halflives.
Radioactivity The property of certain nuclides of showing radioactive decay in which particles or γ radiation are emitted or the nucleus undergoes spontaneous fission.
Speciation Characterization of physical and chemical states of (actinide) species in a given (chemical) environment.
Transactinide elements Artificial elements beyond the actinide elements, beginning with rutherfordium (Rf), element 104. The heaviest elements, synthesized until now, are the elements 114, 116, and 118. At present, bohrium (Bh), element 107, is the heaviest element which has been characterized chemically; chemical studies of element 108, hassium (Hs), and element 112 are in preparation.
THE ACTINIDE ELEMENTS (actinoids) comprise the 14 elements with atomic numbers 90–103, which follow actinium in the periodic table: thorium (Th), protactinium (Pa), uranium (U), neptunium (Np), plutonium (Pu), americium (Am), curium (Cm), berkelium (Bk), californium (Cf), einsteinium (Es), fermium (Fm), mendelevium (Md), nobelium (No), and lawrencium (Lr). The actinides constitute a unique series of elements which are formed by the progressive filling of the 5 f electron shell. Although not formally an actinide element, actinium (Ac;
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212 Actinide Elements atomicnumber89)isusuallyincludedindiscussionsabout the actinides.
According to the International Union of Pure and Applied Chemistry (IUPAC), the name actinoid is preferable to actinide because the ending “-ide” normally indicates a negative ion. However, owing to wide current use, “actinide” is still allowed.
A. Naturally Occurring Actinides
All of the isotopes of the actinide elements are radioactive, and only four of the primordial isotopes, 232Th, 235U, 238U, and 244Pu, have a sufficient long half-life for there to be any of these isotopes left in nature. Only three actinide elements and actinium were known as late as 1940. In addition to thorium and uranium, protactinium and actinium have been found to exist in uranium and thorium ores due to the 238U [Eq. (1)] and 235U [Eq. (2)] decay series:
It was not until 1971 that the existence of primordial 244Pu in nature in trace amounts was shown by D. C. Hoffman and co-workers.
Uranium was the first actinide element to be discovered.M.H.Klaprothshowedin1789thatpitchblendecontained 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, Canada, South Africa, and the United States. The two most important oxide minerals of uranium are uraninite pitchblende, and carnotite (K2(UO2)(VO4)2 ·3H2O; 54% uranium). A very common uranium mineral is autu-
isotope 235U. A third important isotope, 233U, does not occur in nature but can be produced by thermal-neutron irradiation of 232Th [Eq. (3)]:
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