DOCSLIB.ORG

The Periodic Table

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Periodic Table Radiochim. Acta 2019; 107(9–11): 865–877 Robert Eichler* The periodic table – an experimenter’s guide to transactinide chemistry https://doi.org/10.1515/ract-2018-3080 typical for alkali metals, or as H−, similar to halogens. Received November 14, 2018; accepted February 18, 2019; published It becomes metallic at high pressures [3]. Helium has online March 16, 2019 the most enhanced chemical inertness amongst all elements with the highest first ionization potential Abstract: The fundamental principles of the periodic table and lowest polarizability leading to an extremely low guide the research and development of the challenging boiling point of −268.9 °C, close to absolute zero. Fur- experiments with transactinide elements. This guidance thermore, it shows a rare state of superfluidity as a is elucidated together with experimental results from gas liquid below ~−271 °C. phase chemical studies of the transactinide elements with – The group of alkali metals exhibited at the left-hand the atomic numbers 104–108 and 112–114. Some deduced edge of the periodic table represents the most reactive chemical properties of these superheavy elements are pre- metals with increasing reactivity along the group. The sented here in conjunction with trends established by the heavier members even ignite at room temperature in periodic table. Finally, prospects are presented for further contact with air. chemical investigations of transactinides based on trends – On the right-hand edge of the periodic table the group in the periodic table. of noble gases reveals unprecedented atomic stabili- Keywords: Periodic table, trends, transactinides, gas ties and thus exceptional chemical inertness, fading phase, predictions. along the group, though. – The lower edge of the periodic table is home of the heaviest elements, known as transactinide elements 1 Introduction (TA) or superheavy elements (SHE). The TA series includes elements from various groups of the periodic The periodic table is the most fundamental ordering table (see Figure 1). scheme of the 118 chemical elements currently known. Elements with comparable chemical properties were the This work intends to introduce some of the challenges to initial reason already in 1869 for Mendeleev [1, 2] to shape experimentally address chemical properties of these ele- the periodic table similar to the one we know today. At this ments. These efforts are guided by principles of the perio- time, nothing was known about atomic structure and par- dicity. Therefore, some experimentally derived chemical ticularly about electrons governing the chemical proper- properties will be presented in comparison to expectations ties of the elements. However, also the development of our from chemical trends established in the corresponding knowledge about atomic and electronic structure did not groups of the periodic table. change the scope and principal arrangements in the peri- odic table, exhibiting the fundamentality of Mendeleev’s discovery, who had at hand only 66 elements. 2 Trends in the periodic table Figure 1 shows today’s periodic table as approved by the International Union of Pure and Applied Chemistry The concept of groups in the periodic table means not only (IUPAC). The elements featuring the very edges of the peri- that elements with similar chemical properties belong to odic table have particularly exciting properties: one group (column) but also that there are trends estab- – H and He placed on the upper edge, being the most lished for these properties evolving along the groups. abundant atomic matter in our universe, are special Typical properties for which such trends have been estab- elements regarding physical and chemical proper- lished within the groups containing transactinide ele- ties. Hydrogen occurs in compounds either as H+, ments are listed in Figure 2: e. g. for transition metals of groups 4–8 the trend of increasing stability of the com- *Corresponding author: Robert Eichler, Laboratory of pounds with highest oxidation states is observed. Vice Radiochemistry, Paul Scherrer Institute, Forschungsstrasse 111, 5232 versa the stability of the lower oxidation states decrease. Villigen PSI, Switzerland, E-mail: [email protected] The volatility of the compounds with the highest oxidation Bereitgestellt von | Lib4RI Eawag-Empa Angemeldet Heruntergeladen am | 21.10.19 13:17 866 R. Eichler, Experimenter’s guide to transactinide chemistry Figure 1: The IUPAC periodic table of the elements [https://iupac.org/what-we-do/periodic-table-of-elements/]. Figure 2: Definitions of some properties of elements in the periodic table and of their compounds relevant to transactinide chemistry. Typical trends of properties along the groups (with increasing Z) of main group elements (groups: 1–2, 13–18) and transition metals (groups: 3–12) are indicated. Bereitgestellt von | Lib4RI Eawag-Empa Angemeldet Heruntergeladen am | 21.10.19 13:17 R. Eichler, Experimenter’s guide to transactinide chemistry 867 states is highest but it decreases along the group. Along of thermodynamic state functions can help to linearize the members of main groups 1, 2, 13–17, e. g. an increasing trends in the periodic table since state functions are all metallic character or a decreasing acidic character of their influenced by relativistic effects. Thus, predictions can be oxides is observed. made by extrapolation from these trends. However, this requires at least the prediction or the experimental result for one of the thermodynamic state functions used. In an 3 The chemical investigation of increasing number of cases predictions of single atomic behavior or macroscopic properties can be derived using transactinides modern relativistic density functional theory (see for review [11, 12]). Those predictions perpetually improve, 3.1 Relativity in TA chemistry well correlated to the availability of computing power, but also due to excellent methodical developments. Nowa- Generally, the electronic configurations determine the days, even solid state calculations appear possible for chemical properties of the elements. This electronic struc- SHE [13, 14]. ture is more and more influenced by the high electrostatic fields induced by the large nuclear charges (Z) of the heaviest atoms. Strong Coulomb fields force the electrons 3.2 The production of TA with zero angular momentum (s and p1/2) in close vicinity of the nucleus to speed up to velocities of substantial frac- Lacking their occurrence in nature [15], the superheavy tions of the speed of light. This has the primary relativistic elements are produced artificially in heavy-ion induced consequence of increasing mass and thus of a stronger nuclear fusion reactions (see for review [16, 17]). The binding of the corresponding electrons in the atom. These involved nuclear processes are not topic here. Briefly, the electron orbitals contract as a consequence of the primary most important features of this production path relevant relativistic effect and thus increasingly shield the nuclear for the subsequent chemical studies are: charge against the other electrons. Thus, the other orbit- – The complete nuclear fusion process of heavy ions als, with higher angular momentum (p3/2, d, and f) observe with the irradiated target atoms is an exceptionally a lower effective nuclear charge and become thus more rare process leading to production rates of transacti- diffuse and less bound. Additionally the spin-orbit cou- nides in the range from several atoms per minute up pling leads to an energetic split of orbitals with different to single atoms per several days [18]; angular momenta, seen as the third relativistic effect [4, – The SHE production is accompanied by the production 5] (see for review [6, 7]). The pictorial representations of of partial fusion products, in so-called multi-nucleon electron orbitals by White in 1931 [8, 9] reveal impressively transfer reactions, occurring at orders of magnitude how relativistic effects lead to strong changes in orbital higher rates [19], which produce isotopes of elements geometry, electron density, and binding energy, when of almost the entire periodic table, some of which describing the electronic structure of atoms according to might interfere with the detection of the transactinide Dirac’s combination of Schrödinger’s quantum mechanics products and have to be separated. with Einstein’s principles of relativity, which was accom- – The produced single atoms of TA elements recoil out plished just 2 years earlier in 1929 [10]. Most obvious is of the production target with the momentum of the the geometric change of the p1/2 orbital, which becomes incoming beam particles. Therefore, the solid irra- spherical and contracted by the primary relativistic effect. diation targets have to be thin enough for the heavy Only much later, the relativistic effects were accounted for atoms to leave the material [20, 21]. observations of particular chemical properties of heavier – The half-lives of the produced TA isotopes known elements such as lanthanides, gold, mercury, thallium, today range from milliseconds up to several seconds or lead [4]. Known trends of properties as observed in only, rarely to minutes and hours (see Figure 3) and the groups and rows of the periodic table contain basi- compilation [22]. cally the principles of relativity already, but the increase of this influence along the group is not expected to be linear. The general expectation is that relativistic effects 3.3 From production to chemistry shall scale roughly with the square of the atomic charge
Load more

Recommended publications
  • Tuning Wettability of Molten Lithium Via a Chemical Strategy for Lithium Metal Anodes
    ARTICLE https://doi.org/10.1038/s41467-019-12938-4 OPEN Tuning wettability of molten lithium via a chemical strategy for lithium metal anodes Shu-Hua Wang1, Junpei Yue1, Wei Dong1,2, Tong-Tong Zuo1,2, Jin-Yi Li1,2, Xiaolong Liu1, Xu-Dong Zhang1,2, Lin Liu1,2, Ji-Lei Shi 1,2, Ya-Xia Yin1,2 & Yu-Guo Guo 1,2* Metallic lithium affords the highest theoretical capacity and lowest electrochemical potential and is viewed as a leading contender as an anode for high-energy-density rechargeable 1234567890():,; batteries. However, the poor wettability of molten lithium does not allow it to spread across the surface of lithiophobic substrates, hindering the production and application of this anode. Here we report a general chemical strategy to overcome this dilemma by reacting molten lithium with functional organic coatings or elemental additives. The Gibbs formation energy and newly formed chemical bonds are found to be the governing factor for the wetting behavior. As a result of the improved wettability, a series of ultrathin lithium of 10–20 μm thick is obtained together with impressive electrochemical performance in lithium metal batteries. These findings provide an overall guide for tuning the wettability of molten lithium and offer an affordable strategy for the large-scale production of ultrathin lithium, and could be further extended to other alkali metals, such as sodium and potassium. 1 CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, CAS Research/Education Center for Excellence in Molecular Sciences, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences (CAS), 100190 Beijing, China.
    [Show full text]
  • X-Ray-Based Spectroscopic Techniques for Characterization of Polymer Nanocomposite Materials at a Molecular Level
    polymers Review X-ray-Based Spectroscopic Techniques for Characterization of Polymer Nanocomposite Materials at a Molecular Level 1, 2,3, 1 4, 1, Dongwan Son y, Sangho Cho y , Jieun Nam , Hoik Lee * and Myungwoong Kim * 1 Department of Chemistry and Chemical Engineering, Inha University, Incheon 22212, Korea; [email protected] (D.S.); [email protected] (J.N.) 2 Materials Architecturing Research Center, Korea Institute of Science and Technology, Seoul 02792, Korea; [email protected] 3 Division of Nano & Information Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Korea 4 Research Institute of Industrial Technology Convergence, Korea Institute of Industrial Technology, Ansan 15588, Korea * Correspondence: [email protected] (H.L.); [email protected] (M.K.) These authors equally contributed to this work. y Received: 3 April 2020; Accepted: 23 April 2020; Published: 4 May 2020 Abstract: This review provides detailed fundamental principles of X-ray-based characterization methods, i.e., X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, and near-edge X-ray absorption fine structure, and the development of different techniques based on the principles to gain deeper understandings of chemical structures in polymeric materials. Qualitative and quantitative analyses enable obtaining chemical compositions including the relative and absolute concentrations of specific elements and chemical bonds near the surface of or deep inside the material of interest. More importantly, these techniques help us to access the interface of a polymer and a solid material at a molecular level in a polymer nanocomposite. The collective interpretation of all this information leads us to a better understanding of why specific material properties can be modulated in composite geometry.
    [Show full text]
  • Surface Reactions and Chemical Bonding in Heterogeneous Catalysis
    Surface reactions and chemical bonding in heterogeneous catalysis Henrik Öberg Doctoral Thesis in Chemical Physics at Stockholm University 2014 Thesis for the Degree of Doctor of Philosophy in Chemical Physics Department of Physics Stockholm University Stockholm 2014 c Henrik Oberg¨ ISBN 978-91-7447-893-8 Abstract This thesis summarizes studies which focus on addressing, using both theoretical and experimental methods, fundamental questions about surface phenomena, such as chemical reactions and bonding, related to processes in heterogeneous catalysis. The main focus is on the theoretical approach and this aspect of the results. The included articles are collected into three categories of which the first contains detailed studies of model systems in heterogeneous catalysis. For example, the trimerization of acetylene adsorbed on Cu(110) is measured using vibrational spectroscopy and modeled within the framework of Density Functional Theory (DFT) and quantitative agreement of the reaction barriers is obtained. In the second category, aspects of fuel cell catalysis are discussed. O2 dissociation is rate-limiting for the reduction of oxygen (ORR) under certain conditions and we find that adsorbate-adsorbate interactions are decisive when modeling this reaction step. Oxidation of Pt(111) (Pt is the electrocatalyst), which may alter the overall activity of the catalyst, is found to start via a PtO-like surface oxide while formation of a-PtO2 trilayers precedes bulk oxidation. When considering alternative catalyst materials for the ORR, their stability needs to be investigated in detail under realistic conditions. The Pt/Cu(111) skin alloy offers a promising candidate but segregation of Cu atoms to the surface is induced by O adsorption.
    [Show full text]
  • Inorganic Chemistry for Dummies® Published by John Wiley & Sons, Inc
    Inorganic Chemistry Inorganic Chemistry by Michael L. Matson and Alvin W. Orbaek Inorganic Chemistry For Dummies® Published by John Wiley & Sons, Inc. 111 River St. Hoboken, NJ 07030-5774 www.wiley.com Copyright © 2013 by John Wiley & Sons, Inc., Hoboken, New Jersey Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permis- sion of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 646-8600. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley. com/go/permissions. Trademarks: Wiley, the Wiley logo, For Dummies, the Dummies Man logo, A Reference for the Rest of Us!, The Dummies Way, Dummies Daily, The Fun and Easy Way, Dummies.com, Making Everything Easier, and related trade dress are trademarks or registered trademarks of John Wiley & Sons, Inc. and/or its affiliates in the United States and other countries, and may not be used without written permission. All other trade- marks are the property of their respective owners. John Wiley & Sons, Inc., is not associated with any product or vendor mentioned in this book.
    [Show full text]
  • (XPS) • X-Ray Photoelectron Spectroscopy
    Introduction to X-ray Photoelectron Spectroscopy (XPS) • X-ray Photoelectron Spectroscopy (XPS), also known as Electron Spectroscopy for Chemical Analysis (ESCA) is a widely used technique to investigate the chemical composition of surfaces. • XPS which makes use of the photoelectric effect, was developed in the mid-1960’s by Kai Siegbahn and his research group at the University of Uppsala, Sweden. Photoemission of Electrons Ejected Photoelectron Incident X-ray Free Electron Level (vacuum) Conduction Band Fermi Level Valence Band ¾ XPS spectral lines are identified by the shell from which the electron was ejected 2p L2,L3 (1s, 2s, 2p, etc.). ¾ The ejected photoelectron has kinetic 2s L1 energy: ¾ KE= hv – BE - φ 1s K 1s K ¾ Following this process, the atom will release energy by the emission of a photon or Auger Electron. Auger Electron Emission Free Electron Level Conduction Band Conduction Band Fermi Level Valence Band Valence Band 2p 2p L2,L3 2s 2s L1 1s 1s K ¾ L electron falls to fill core level vacancy (step 1). ¾ KLL Auger electron emitted to conserve energy released in step 1. ¾ The kinetic energy of the emitted Auger electron is: KE=E(K)-E(L2)-E(L3). XPS Energy Scale - Binding energy BEBE == hvhv -- KEKE -- ΦΦspec Where: BE= Electron Binding Energy KE= Electron Kinetic Energy Φspec= Spectrometer Work Function Photoelectron line energies: Not Dependent on photon energy. Auger electron line energies: Dependent on photon energy. XPS spectrum of Vanadium Auger electrons Note the stepped background • Only electrons close to surface
    [Show full text]
  • Lecture 17 Auger Electron Spectroscopy Auger – History Cloud Chamber
    Lecture 17 Auger Electron Spectroscopy Auger – history cloud chamber Although Auger emission is intense, it was not used until 1950’s. Evolution of vacuum technology and the application of Auger Spectroscopy - Advances in space technology Various ways to estimate Auger electron kinetic energy (z) (z) EKL1 L23 = Ek –EL1 –EL23 (z + ) - A (z) (z) (z) (z) = Ek –EL1 –EL23 - [EL2,3 (z+1) – EL2,3 ] Exyz = Ex –½(Ex(z) + Ey(z+1)) – ½ (E2(z) + E2(z+1)) - A has been found to vary from 0.5 + 1.5. Relaxation more important than ESCA. Auger energy is independent of sample work function. Electron loses energy equal to the work function of the sample during emission but gains or loses energy equal to the difference in the work function of the sample and the analyser. Thus the energy is dependent only on the work function of the analyser. Use of dN(E)/dE plot Instrumentation Early analysers What happens to the system after Auger emission Chemical differences When core electrons are involved in Auger, the chemical shifts are similar to XPS. - For S2O3 , the chemical shifts between +6 and –2 oxidation states are 7eV for k shell and 6 eV for p. The chemical shift for Auger is given as E = E1 -2E (LII,III) = 5 eV The experimental value is 4.7 eV Chemical sifts of core levels - change in relaxation energy. Characteristics Electron and photon excitation (XAES). Auger emission is possible for elements z >3. Lithium is a special case. No Auger in the gas phase but shows in the solid state.
    [Show full text]
  • Oxidation State Analyses of Uranium with Emphasis on Chemical Speciation in Geological Media
    University of Helsinki View metadata, citation and similar papers at core.ac.uk Faculty of Science brought to you by CORE Department of Chemistry provided by Helsingin yliopiston digitaalinen arkisto Laboratory of Radiochemistry Finland OXIDATION STATE ANALYSES OF URANIUM WITH EMPHASIS ON CHEMICAL SPECIATION IN GEOLOGICAL MEDIA Heini Ervanne Academic Dissertation To be presented with the permission of the Faculty of Science of the University of Helsinki for public criticism in the Main lecture hall A110 of the Kumpula Chemistry Department on May 14th, 2004, at 12 o’clock noon. Helsinki 2004 ISSN 0358-7746 ISBN 952-10-1825-9 (nid.) ISBN 952-10-1826-7 (PDF) http://ethesis.helsinki.fi Helsinki 2004 Yliopistopaino ABSTRACT OXIDATION STATE ANALYSES OF URANIUM WITH EMPHASIS ON CHEMICAL SPECIATION IN GEOLOGICAL MEDIA This thesis focuses on chemical methods suitable for the determination of uranium redox species in geological materials. Nd-coprecipitation method was studied for the determination of uranium oxidation states in ground waters. This method is ideally suited for the separation of uranium oxidation states in the fi eld, which means that problems associated with the instability of U(IV) during transport are avoided. An alternative method, such as ion exchange, is recommended for the analysis of high saline and calcium- and iron-rich ground waters. U(IV)/Utot was 2.8- 7.2% in ground waters in oxidizing conditions and 60-93% in anoxic conditions. From thermodynamic model calculations applied to results from anoxic ground waters it was concluded that uranium can act as redox buffer in granitic ground waters. An ion exchange method was developed for the analysis of uranium oxidation states in different solid materials of geological origin.
    [Show full text]
  • Effect of Sodium Chloride on Some of the Chemical Reactions of Sodium Nitrite in Cured Meat Taekyu Park Iowa State University
    Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1984 Effect of sodium chloride on some of the chemical reactions of sodium nitrite in cured meat Taekyu Park Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Agriculture Commons, and the Food Science Commons Recommended Citation Park, Taekyu, "Effect of sodium chloride on some of the chemical reactions of sodium nitrite in cured meat " (1984). Retrospective Theses and Dissertations. 8208. https://lib.dr.iastate.edu/rtd/8208 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. INFORMATION TO USERS This reproduction was made from a copy of a document sent to us for microfilming. While the most advanced technology has been used to photograph and reproduce this document, the quality of the reproduction is heavily dependent upon the quality of the material submitted. The following explanation of techniques is provided to help clarify markings or notations which may appear on this reproduction. 1.The sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s)". If it was possible to obtain the missing page(s) or section, they are spHced into the film along with adjacent pages. This may have necessitated cutting througli an image and duplicating adjacent pages to assure complete continuity.
    [Show full text]
  • Chromatography & Spectroscopy
    © 2020 IJRAR March 2020, Volume 7, Issue 1 www.ijrar.org (E-ISSN 2348-1269, P- ISSN 2349-5138) A Brief Study About Analytical Techniques In Pharmaceutical Analysis (Chromatography & Spectroscopy):A Review Article 1 Diksha Jindal, 2 Hardeep, 3 Pallvi, 4 R. K. Patil, 5 H. C. Patil 1 Associate Professor, 2 Pharm. D Student, 3 Pharm. D Student, 4 Dean Academics, 5 Principal of AIPBS 1 Adesh Institute of Pharmacy and Biomedical Sciences 1 Adesh University, Bathinda ( Punjab ), India ABSTRACT:- Now a days, pharmaceutical products brought a great revolt in human health. These pharmaceuticals products would show their impact on individuals only if they are free from impurities & administered in an adequate quantity. Pharmaceutical products may attain impurities at various levels of their development or manufacture, storage and transportation which make the pharmaceutical product risky to be administered. Thus, at different stages of their development the impurities must be detected and they must be quantified in which analytical techniques play important roles. This review highlights the spectroscopic techniques like UV - Visible, IR, NMR and chromatographic techniques like HPLC, TLC with their corresponding methods with applications, principles and instrumentations that have been applied in analysis of various pharmaceutical products. In the conclusion we will find out the most widely used and advanced analytical technique with greater advantages and efficiency in pharmaceuticals analysis. [ 1 ] KEYWORDS: - Analytical techniques, Pharmaceuticals, Spectroscopy, Chromatography. 1. INTRODUCTION: - The process of development of drug starts with the innovation of a drug molecule that has showed therapeutic effects to control diagnosis or to cure disease. The drug molecule which shows some therapeutic effect is known as Active Pharmaceutical Ingredient (API).
    [Show full text]
  • Study and Interpretation of the Chemical Characteristics of Natural Water Second Edition
    Study and Interpretation of the Chemical Characteristics of Natural Water Second Edition GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1473 Study and Interpretation of the Chemical Characteristics of Natural Water Second Edition By JOHN D. HEM GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1473 A review of chemical, geologic, and hydrologic principles and processes that control the composition of natural water, with methods for studying and interpreting chemical analyses UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1970 UNITED STATES DEPARTMENT OF THE INTERIOR WALTER J. HICKEL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director Library of Congress catalog-card No. 73-606921 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.G. 20402 - Price $2.25 (paper cover) PREFACE Most of the text of the first edition of this publication, U.S. Geologi­ cal Survey Water-Supply Paper 1473, was written in 1955 and 1956. When the plans were being made for the report a few years earlier, the expectation was that it would be used within the U.S. Geological Survey for the most part as a guide for field investigators to help in determining and interpreting the chemical quality of water resources. At the same time, however, a substantial increase of interest and activity in the fields of natural-water chemistry and waterrpollution control was beginning to be noticeable, and, as a result, when the report was published in 1959, it soon attained a considerably wider circulation than had originally been anticipated. A series of reprintings was necessary. This revision of the earlier book has been prepared because of the continued and still-growing interest in the subject matter.
    [Show full text]
  • Chemical Activity of Noble Gases Kr and Xe and Its Impact on Fission Gas Accumulation in the Irradiated UO2 Fuel
    6TH INTERNATIONAL CONFERENCE ON WWER FUEL PERFORMANCE, MODELLING AND EXPERIMENTAL SUPPORT, 19 - 23 September 2005, Albena Congress Center, Bulgaria Chemical activity of noble gases Kr and Xe and its impact on fission gas accumulation in the irradiated UO2 fuel. Marcin Szuta Institute of Atomic Energy, Otwock-Świerk 05-400, Poland, E-mail: [email protected] Abstract It is generally accepted that most of the insoluble inert gas atoms Xe and Kr produced during fissioning are retained in the fuel irradiated at a temperature lower than the threshold. Experimental data imply that we can assume that after irradiation exposure in excess of 1018 fissions/cm3 the single gas atom diffusion can be disregarded in description of fission gas behaviour. It is assumed that the vicinity of the fission fragment trajectory is the place of intensive irradiation induced chemical interaction of the fission gas products with UO2. Significant part of fission gas product is thus expected to be chemically bound in the matrix of UO2. From the moment of discovering the rare gases (helium, neon, argon, krypton, xenon and radon) at the end of XIX century until to the beginning of sixties years of XX century it was considered that the noble gases are chemically inactive. The nobility of rare gases started to deteriorate after when the first xenon compound was found by Barlett in 1962. Barlet showed that the noble gases are capable of forming what one could consider as normal chemical compounds, compelling chemists to readjust considerably their thinking regarding these elements. In a burst of activity in the years that followed, a number of compounds of noble gases have been reported.
    [Show full text]
  • X Ray Photoelectron Spectroscopy
    X■Ray Photoelectron Spectroscopy Binayak Panda, Marshall Space Flight Center / NASA General Uses • Charging effects may be a problem with insulating • Elemental analysis of surfaces of all elements samples. Some instruments are equipped with Lithium and higher charge-compensation devices • Analyses the first few atomic layers on samples Estimated Analysis Time • Thin surface layers that cannot be analyzed by other • Requires few hours of vacuum pump down before techniques analysis • Chemical state identification of surface elements • Qualitative analysis can be performed in 5 to 10 • In-depth composition profiles for elemental minutes distribution as well as oxidation states in • Quantitative analysis requires 1 h to several hours, samples depending on information desired • Surface analysis of samples when destructive effects Capabilities of Related Techniques of electron or ion beam techniques must be avoided • Auger electron spectroscopy: Compositional analysis Examples of Applications of surfaces. Faster, with better lateral resolution than • Determination of oxidation states of metal atoms in XPS. Has depth-profiling capabilities. Electron beam metal compounds can be very damaging; bonding and other chemical • Identification of surface contaminations state information are not easily interpreted. Very thin • Measurement of surfaces film thickness surface layers cannot be analyzed. • Identification and degradation of polymers • Low-energy ion-scattering spectroscopy: Sensitive to the top atomic layer of the surface and has profiling Samples capabilities. Quantitative analysis requires use of • Form : Flat solids with low vapor pressure are preferred standards; no chemical state information; poor mass • Size : Depends on machine – up to 4 inches resolution for high-Z elements • Preparation: Must be free of fingerprints, oils, or • Ultraviolet Photoelectron spectroscopy (UPS): UPS surface contamination operates with the same principles as the XPS, the exciting radiation in this case is the ultraviolet light with a narrow Limitations band of wavelength.
    [Show full text]