DOCSLIB.ORG

{DOWNLOAD} Chemical Bonding Ebook

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
{DOWNLOAD} Chemical Bonding Ebook CHEMICAL BONDING PDF, EPUB, EBOOK Mark J. Winter | 128 pages | 05 May 2016 | Oxford University Press | 9780198700951 | English | Oxford, United Kingdom Introduction to Chemical Bonding - Chemistry LibreTexts The most common bond in organic molecules, a covalent bond involves the sharing of electrons between two atoms. The pair of shared electrons forms a new orbit that extends around the nuclei of both atoms, producing a molecule. There are two secondary types of covalent bonds that are relevant to biology — polar bonds and hydrogen bonds. Two atoms connected by a covalent bond may exert different attractions for the electrons in the bond, producing an unevenly distributed charge. The result is known as a polar bond , an intermediate case between ionic and covalent bonding, with one end of the molecule slightly negatively charged and the other end slightly positively charged. Although the resulting molecule is neutral, at close distances the uneven charge distribution can be important. Water is an example of a polar molecule; the oxygen end has a slight positive charge whereas the hydrogen ends are slightly negative. Polarity explains why some substances dissolve readily in water and others do not. Ionic bond : bond in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other. Other types of bonds include metallic bonds and hydrogen bonding. The attractive forces between molecules in a liquid can be characterized as van der Waals bonds. Covalent chemical bonds involve the sharing of a pair of valence electrons by two atoms, in contrast to the transfer of electrons in ionic bonds. Such bonds lead to stable molecules if they share electrons in such a way as to create a noble gas configuration for each atom. Hydrogen gas forms the simplest covalent bond in the diatomic hydrogen molecule. The halogens such as chlorine also exist as diatomic gases by forming covalent bonds. The nitrogen and oxygen which makes up the bulk of the atmosphere also exhibits covalent bonding in forming diatomic molecules. Covalent bonds in which the sharing of the electron pair is unequal, with the electrons spending more time around the more nonmetallic atom, are called polar covalent bonds. In such a bond there is a charge separation with one atom being slightly more positive and the other more negative, i. The ability of an atom to attract electrons in the presense of another atom is a measurable property called electronegativity. In chemical bonds , atoms can either transfer or share their valence electrons. In the extreme case where one or more atoms lose electrons and other atoms gain them in order to produce a noble gas electron configuration, the bond is called an ionic bond. Typical of ionic bonds are those in the alkali halides such as sodium chloride, NaCl. The properties of metals suggest that their atoms possess strong bonds , yet the ease of conduction of heat and electricity suggest that electrons can move freely in all directions in a metal. The general observations give rise to a picture of "positive ions in a sea of electrons" to describe metallic bonding. Such bonds are neither ionic nor covalent since the participating electrons are not localized on the atoms. The general properties of metals include malleability and ductility and most are strong and durable. They are good conductors of heat and electricity. Their strength indicates that the atoms are difficult to separate, but malleability and ductility suggest that the atoms are relatively easy to move in various directions. The electrical conductivity suggests that it is easy to move electrons in any direction in these materials. The thermal conductivity also involves the motion of electrons. All of these properties suggest the nature of the metallic bonds between atoms. Hydrogen bonding differs from other uses of the word " bond " since it is a force of attraction between a hydrogen atom in one molecule and a small atom of high electronegativity in another molecule. That is, it is an intermolecular force, not an intramolecular force as in the common use of the word bond. Chemical bonds | Chemistry library | Science | Khan Academy Because opposite charges attract, the atoms bond together to form a molecule. The most common bond in organic molecules, a covalent bond involves the sharing of electrons between two atoms. The pair of shared electrons forms a new orbit that extends around the nuclei of both atoms, producing a molecule. There are two secondary types of covalent bonds that are relevant to biology — polar bonds and hydrogen bonds. Two atoms connected by a covalent bond may exert different attractions for the electrons in the bond, producing an unevenly distributed charge. Smaller differences in electronegativity usually occur between elements that are both considered non-metals, so most compounds that are made up from two non-metal atoms are considered to be covalent. If there is a big difference in electronegativity between two different elements, the bond between them will be. Once differences in electronegativity have been considered, and a bond has been determined as being covalent, the story is not quite over. Not all covalent bonds are created equally. The only true, perfectly covalent bond will be one where the difference in electronegativity between the two atoms within the bond is equal to zero. When this occurs, each atom has exactly the same attraction for the electrons that make up the covalent bond, and therefore the electrons are perfectly shared. This typically occurs in diatomic two-atom molecules such as H 2 , N 2 , O 2 , and those of the halogen compounds when the atoms in the bond are identical. However, most covalent bonds occur between elements where even though the electronegativity difference is lower than 1. In these cases, the electrons are still considered shared, that is, the bond is still considered covalent, but the sharing is not perfect. Most covalent bonds are formed between atoms of differing electronegativity , meaning that the shared electrons are attracted to one atom within the bond more than the other. As a result, the electrons tend to spend more time at one end of the bond than the other. One end of the bond is relatively positive less attraction for electrons , and one end of the bond is relatively negative more attraction for electrons. If this difference in electron affinity exists across the molecule , then the molecule is said to be polar — meaning that it will have two different, and opposite, partial charges at either end. Water H 2 O is an excellent example of a polar molecule. Electrons are not shared evenly since hydrogen and oxygen have different electronegativities. This creates dipoles in each H-O bond, and these dipoles do not cancel each other out, leaving the water molecule polar overall Figure 7. Read more about these bonds in our module Properties of Liquids. When the electrons in a bond are perfectly shared, there is no dipole , and neither end of the bond carries any partial charge. When no such overall charge exists, the molecule is said to be non-polar. An example of such a non-polar molecule is hydrogen, H 2. In larger molecules with multiple covalent bonds , each bond will have either no dipole or a dipole with varying degrees of partial charge. When all of these dipoles are taken into consideration in three dimensions, the uneven distribution of charge caused by the dipoles may cancel out, making the molecule non-polar. Alternatively, there may be a partial electrical charge across the molecule , making it a polar molecule. An example of a multiple atom non-polar molecule is carbon dioxide. We have limited our discussion to ionic and covalent bonding and the sliding scale of bond type that exists between them. However, many other types of interactions and bonds between atoms exist, notably metallic bonding the attractions that hold metal atoms together in metallic elements , and intermolecular forces the interactions that exist between, rather than within, covalently bonded molecules. These each involve similar electrostatic interactions to the ones described in ionic and covalent bonds , but even those extensions are far from the end of the bonding story. In , researchers found the first experimental evidence for a new type of interaction between atoms that had been predicted in the s Fleming et al. Named a "vibrational bond," the theory describes a lightweight element in this case, an isotope of hydrogen oscillating or "bouncing" between two much heavier atoms in this case, bromine and effectively holding the larger atoms together. Donald Fleming, a chemist based at the University of British Columbia in Canada, described the new bond as being "like a Ping Pong ball bouncing between two bowling balls. The millions of different chemical compounds that make up everything on Earth are composed of elements that bond together in different ways. This module explores two common types of chemical bonds: covalent and ionic. The module presents chemical bonding on a sliding scale from pure covalent to pure ionic, depending on differences in the electronegativity of the bonding atoms. When a force holds atoms together long enough to create a stable, independent entity, that force can be described as a chemical bond. The known chemical elements interact with one another via chemical bonds, to create brand new, unique compounds that have entirely different chemical and physical properties than the elements that make them up. It is helpful to think of chemical bonding as being on a sliding scale, where at one extreme there is pure covalent bonding, and at the other there is pure ionic bonding. Most chemical bonds lie somewhere between those two extremes. When a chemical bond is formed between two elements, the differences in the electronegativity of the atoms determine where on the sliding scale the bond falls.
Load more

Recommended publications
  • To Vibrational Bonding of Brmubr and Imui Jörn Manz, Kazuma Sato, Toshiyuki Takayanagi, and Takahiko Yoshida
    From photoelectron detachment spectra of BrHBr−, BrDBr− and IHI−, IDI− to vibrational bonding of BrMuBr and IMuI Jörn Manz, Kazuma Sato, Toshiyuki Takayanagi, and Takahiko Yoshida Citation: The Journal of Chemical Physics 142, 164308 (2015); doi: 10.1063/1.4918980 View online: http://dx.doi.org/10.1063/1.4918980 View Table of Contents: http://scitation.aip.org/content/aip/journal/jcp/142/16?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Photoelectron spectroscopy of higher bromine and iodine oxide anions: Electron affinities and electronic structures of BrO2,3 and IO2–4 radicals J. Chem. Phys. 135, 184309 (2011); 10.1063/1.3658858 Photoelectron spectroscopy of the Cl − … H 2 ∕ D 2 anions: A model beyond the rotationless and Franck–Condon approximations J. Chem. Phys. 128, 154317 (2008); 10.1063/1.2894306 Anion photoelectron spectroscopy of solvated transition state precursors J. Chem. Phys. 119, 872 (2003); 10.1063/1.1577331 The influence of the detachment of electrons on the properties and the nature of interactions in X − H 2 O (X=Cl, Br) complexes J. Chem. Phys. 115, 3469 (2001); 10.1063/1.1388046 Determination of the structure of HBr DBr J. Chem. Phys. 106, 6240 (1997); 10.1063/1.474055 This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP: 130.133.152.56 On: Wed, 01 Jul 2015 09:24:46 THE JOURNAL OF CHEMICAL PHYSICS 142, 164308 (2015) From photoelectron detachment spectra of BrHBr−, BrDBr− and
    [Show full text]
  • The Calculation of Electron Collisions with Atoms and Molecules
    The Calculation of Electron Collisions with Atoms and Molecules Thomas Meltzer A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy of University College London. August 10, 2020 2 I, Thomas Meltzer, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the work. Abstract In this thesis electron collisions are studied under two different scattering energy regimes. Firstly, low energy electron-molecule collisions are considered. These typically occur in interstellar medium, planetary atmospheres or industrial plasmas. Under these conditions the electrons cannot be treated classically and so a quan- tum mechanical approach is used. Using R-matrix theory two targets are studied: nitric oxide (NO) and molecular hydrogen (H2). Owing to new developments in the UKRMol+ code the boundaries of previous R-matrix calculations are pushed to new limits in order to produce accurate cross-sections for electron-impact elec- tronic excitation of H2. This includes the use of a B-spline continuum basis, a triply-augmented target basis and a box size of 100 a0. NO is used as a prototypical example of an open-shell molecule that exhibits mixed Rydberg-like and Valence states. Systems like this are typically difficult to solve using standard quantum chemistry approaches, and so the R-matrix with pseudo-states method is employed to produce a set of improved potential energy curves, capable of being used in fur- ther scattering calculations. In the second regime, high energy electron-atom collisions are investigated.
    [Show full text]
  • Wave Algorithms: Optimal Database Search and Catalysis
    Wave Algorithms: Optimal Database Search and Catalysis1 Apoorva D. Patel Centre for High Energy Physics and Supercomputer Education and Research Centre Indian Institute of Science, Bangalore-560012, India Abstract. Grover’s database search algorithm, although discovered in the context of quantum computation, can be implemented using any physical system that allows superposition of states. A physical realization of this algorithm is described using coupled simple harmonic oscillators, which can be exactly solved in both classical and quantum domains. Classical wave algorithms are far more stable against decoherence compared to their quantum counterparts. In addition to providing convenient demonstration models, they may have a role in practical situations, such as catalysis. Keywords: Grover’s database search algorithm, Catalysis, Resonance PACS: 03.67.Lx, 34.10.+x, 46.40.-f COMPUTING WITH WAVES Any physical system—with some initial state, some final state, and some interaction in between—is a candidate for processing information. One only needs to construct a suitable map between physical properties of the system and abstract mathematical vari- ables. Most of the development in computer algorithms has been in the framework of “particle-like" discrete digital languages. It is known that “wave-like" analogue compu- tation can also be carried out (e.g. using RLC circuits), but that has not been explored as intensively. The obvious reason is that discrete variables allow a degree of precision, by implementation of error correction procedures, that continuous variables cannot pro- vide. In addition, computational complexity is believed to be the same for digital and analogue algorithms, so the choice between the two is left to considerations of hardware arXiv:quant-ph/0609042v2 20 Dec 2006 stability.
    [Show full text]
  • Developing Reactive Molecular Dynamics for Understanding Polymer Chemical Kinetics Kenneth D
    University of Massachusetts Amherst ScholarWorks@UMass Amherst Open Access Dissertations 5-2009 Developing Reactive Molecular Dynamics for Understanding Polymer Chemical Kinetics Kenneth D. Smith University of Massachusetts Amherst, [email protected] Follow this and additional works at: https://scholarworks.umass.edu/open_access_dissertations Part of the Polymer Science Commons Recommended Citation Smith, Kenneth D., "Developing Reactive Molecular Dynamics for Understanding Polymer Chemical Kinetics" (2009). Open Access Dissertations. 80. https://doi.org/10.7275/9d4y-2g78 https://scholarworks.umass.edu/open_access_dissertations/80 This Open Access Dissertation is brought to you for free and open access by ScholarWorks@UMass Amherst. It has been accepted for inclusion in Open Access Dissertations by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. DEVELOPING REACTIVE MOLECULAR DYNAMICS FOR UNDERSTANDING POLYMER CHEMICAL KINETICS A Dissertation Presented by KENNETH D SMITH Submitted to the Graduate School of the University of Massachusetts Amherst in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY May 2009 Chemical Engineering c Copyright by Kenneth D Smith 2009 All Rights Reserved DEVELOPING REACTIVE MOLECULAR DYNAMICS FOR UNDERSTANDING POLYMER CHEMICAL KINETICS A Dissertation Presented by KENNETH D SMITH Approved as to style and content by: Phillip R. Westmoreland, Chair Dimitrios Maroudas, Member Murugappan Muthukumar, Member T. J. Mountziaris, Department Head Chemical Engineering ACKNOWLEDGMENTS While at UMASS there have been many challenges, but after all that is what a dissertation is all about. While the challenges of fire safe polymers, reactive molecular dynamics, and everything else are not yet resolved, the challenge of finishing the dissertation is completed.
    [Show full text]
  • Conference Series
    CONFERENCE SERIES Series Editors: Birgit Holzner, Tilmann D. Märk innsbruck university press © innsbruck university press, 2012 Universität Innsbruck 1st edition All rights reserved. Cover design: Carmen Drolshagen Cover photo: © Laurent Salino / Office du tourisme Alpe d‘Huez Printed by Prime Rate Kft. www.uibk.ac.at/iup ISBN 978-3-902719-52-2 Marius Lewerenz, Odile Dutuit, Roberto Marquardt (Eds.) XVIIIth Symposium on Atomic, Cluster and Surface Physics 2012 (SASP 2012) January 22 - 27, 2012 Alpe d‘ Huez, France Contributions XVIIIth Symposium on Atomic, Cluster and Surface Physics (SASP 2012) January 22-27, 2012 Alpe d’Huez, France International Scientific Committee: Davide Bassi (Universitá degli Studi di Trento, Italy) Tilmann D. Märk (Universität Innsbruck, Austria) Nigel Mason (Open University, UK) Martin Quack (Eidgenössische Technische Hochschule Zürich, Switzerland) Tom Rizzo (EPFL Lausanne, Switzerland) Paul Scheier (Universität Innsbruck, Austria) Organising Committee: Local organisation: Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), France Odile Dutuit (IPAG) and Roberto Marquardt (Univ. Strasbourg), co-chairpersons Marius Lewerenz (Univ. Paris-Est, Marne la Vallée) Cecilia Ceccarelli (IPAG) Vianney Taquet (IPAG) Nigel Mason (Open Univ., UK) Valérie Chopin (IPAG) Béatrice Pibaret (IPAG) SASP 2012 was sponsored by the EU through the COST Action on the “Chemical Cosmos”, Université Paris Est (Marne la Vallée), CNRS-INSU, and IPAG (Institut de Planétologie et d’Astrophysique de Grenoble). 2012 5 Preface The international symposium on Atomic, Cluster and Surface Physics, SASP, is one in a continuing biennial series of conferences founded in 1978 by members of the Institute for Ion Physics and Applied Physics of the University of Innsbruck, Austria.
    [Show full text]
  • Theoretical Study of the H + Br2 and Mu + Br2 Reactions: a New Ab Initio Potential Energy Surface and Quantum Dynamics Calculations
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Saitama University Cyber Repository of Academic Resources Theoretical study of the H + Br2 and Mu + Br2 reactions: A new ab initio potential energy surface and quantum dynamics calculations Toshiyuki Takayanagi Department of Chemistry, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama 338-8570, Japan Abstract A new global potential energy surface for the H + Br2 → HBr + Br reaction has been developed at the MRCI+Q/ang-cc-pVTZ ab initio level of theory. It has been found that this level calculation gives a negative barrier slightly below the H + Br2 reactant energy level. Time-dependent and time-independent quantum dynamics calculations have been performed on this potential energy surface. The calculated cumulative reaction probabilities for J = 0 around the reaction threshold energy region show a very similar behavior for both the H + Br2 and Mu + Br2 reaction, in qualitative disagreement with experimental measurements, where a positive activation energy was observed for the H + Br2 reaction while a negative activation energy for the Mu + Br2 reaction. Variational calculations of vibrational energy levels have also been performed to study dynamical vibrational bonding for the Br-Mu-Br molecule. It has been found that the system has several vibrational bonding states, whose wave functions are localized around the transition-state of the Br + MuBr' → MuBr + Br' exchange reaction, below the lowest Br + MuBr asymptotic energy level. This result qualitatively supports the recent experimental finding that a long-lived radical containing a Mu atom is produced in the Mu + Br2 reaction.
    [Show full text]
  • Download Author Version (PDF)
    PCCP Accepted Manuscript This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. www.rsc.org/pccp Page 1 of 21 Physical Chemistry Chemical Physics Influence of vibration in the reactive scattering of D+MuH: The effect of dynamical bonding V. S´aez-R´abanos∗ Departamento de Sistemas y Recursos Naturales. E.T.S. de Ingenier´ıade Montes, Forestal y del Medio Natural. Universidad Polit´ecnica de Madrid, 28040 Madrid, Spain J. E. Verdasco and F. J. Aoiz Departamento de Qu´ımica F´ısica, Facultad de Qu´ımica, Manuscript Universidad Complutense de Madrid (Unidad Asociada CSIC), 28040 Madrid, Spain V. J. Herrero Instituto de Estructura de la Materia (IEM{CSIC), Serrano 123, 28006 Madrid, Spain (Dated: April 14, 2016) Accepted Physics Chemical Chemistry Physical i Physical Chemistry Chemical Physics Page 2 of 21 Abstract The dynamics of the D+MuH(v=1) reaction has been investigated using time-independent quan- tum mechanical calculations.
    [Show full text]
  • Thesis Submitted to the Faculty of the University of Mississippi in Partial Fulfillment of the Requirements of the Sally Mcdonnell Barksdale Honors College
    Spectroscopic and Computational Studies of the Hydrogen Bonding Interactions of Hydroxyethyl Ethers By: Ashley Williams A thesis submitted to the faculty of The University of Mississippi in partial fulfillment of the requirements of the Sally McDonnell Barksdale Honors College. Oxford, MS May 2017 Approved by: Dr. Nathan I. Hammer Advisor Dr. Steven R. Davis Reader Dr. John Samonds Reader i ©2017 Ashley Elizabeth Williams ALL RIGHTS RESERVED ii Acknowledgements The University of Mississippi has blessed me with opportunities I would have never thought possible upon embarking on my college journey. The countless people who have mentored me and helped ensure my success is astounding. First I would like to thank Dr. Nathan Hammer for his consistent faith in me, and his insistence that I do not quit when things get hard. His guidance and wisdom have been paramount in making me both the student and person that I am today. The Ole Miss Women’s Council has also been integral in facilitating my success at Ole Miss, as they provided me with weekly guidance and a home away from home, as well as a leg up in my academic and career goals with interview practices, resume-building sessions, and leadership conferences. I would like to thank my lab group, the Hammer group, particularly Shane Autry and Louis McNamara, for their constant source of knowledge and help constructing my matrix isolation Raman spectrometer. Finally, I would like to thank my parents, Suzy and Wayne Williams, and my sister, Anna Katherine Williams, for the tremendous amount of support, love, and encouragement over the years.
    [Show full text]
  • Fish Grind Teeth to Grunt Haemorrhagic Fever
    Selections from the RESEARCH HIGHLIGHTS scientific literature VIROLOGY Improved mouse for Ebola research To overcome the lack of good mouse models for Ebola studies, researchers have created a mouse that displays the hallmark symptoms of Ebola infection — potentially useful for drug and vaccine development. A team led by Michael O’NEILL/OCEANWIDEIMAGES.COM MICHAEL PATRICK Katze at the University of Washington, Seattle, crossed eight strains of mice to produce a colony with a diverse genetic background. When infected with a mouse-adapted version of the Ebola virus, the mice ZOOLOGY exhibited a broad range of responses from no observable symptoms to severe Fish grind teeth to grunt haemorrhagic fever. Surviving mice showed A species of fish makes grunting sounds by animals and found that the sound-making key physiological differences grinding its teeth. The French grunt fish process was similar to chewing, but slightly compared with susceptible (Haemulon flavolineatum; pictured) is thought slower. Electron microscope images of the teeth animals, such as immune to groan in distress by rubbing together its revealed signs of erosion. cells that function better. pharyngeal jaws, a second pair of toothed jaws The fish’s hearing is not tuned specifically to The researchers link these located in the throat that help to process food. the frequencies of the grunts, suggesting that differences to variants of the Frédéric Bertucci of the University of Liége the pharyngeal jaws first evolved for eating and genes Tie1 and Tek. in Belgium and his co-workers used X-ray were later co-opted for communication. Science http://doi.org/ws4 (2014) cameras to capture high-speed video of the J.
    [Show full text]
  • 2020:08 Identifying Radiologically Important ESS-Specific Radionuclides and Relevant Detection Methods
    Research Identifying radiologically important ESS-specific radionuclides and relevant detection methods 2020:08 Authors: Kristina Eriksson Stenstrm, Vytenis Barkauskas, Guillaume Pedehontaa-Hiaa, Charlotta Nilsson, Christopher Rääf, Hanna Holstein, Sren Mattsson, Johan Martinsson, Mattias Jnsson, Christian Bernhardsson Lunds universitet, Lund Report number: 2020:08 ISSN: 2000-0456 Available at: www.ssm.se SSM 2020:08 SSM perspective Background The European Spallation Source (ESS) facility is under construction in Lund, Sweden. High-energy protons will be accelerated in a linear accel- erator and generate neutrons when hitting a rotating target of tungsten. This spallation process will also generate a wide range of diferent radio- active by-products of which a small part will be released to the environ- ment during normal operation. Furthermore, in case of an accident scenario, gases and aerosols might be released from the tungsten target. Emissions from ESS, both during normal operation or in case of an acci- dent, will difer in radionuclide composition to the environment from those activities with ionising radiation that we have experience from in Sweden today. Thus, the Swedish Radiation Safety Authority has found it of great importance to support the possibilities to increase the knowl- edge about measurement and analysis of ESS-specifc radionuclides that could be useful in the environmental monitoring program when the ESS facility starts to generate neutrons in a few years. Results Based on an extensive literature review of ESS-relevant radionuclides the authors concluded that radionuclide production in particle accelerators is well known, while experience with tungsten targets is very limited. The authors showed a good agreement with results of others, except for 148 Gd, and that the calculated radionuclide composition is sensitive to the nuclear interaction models used by developing an independent simplifed model of the ESS target sector for the calculations of radionu- clide production in the ESS target.
    [Show full text]
  • Chemistry Musing Was Started from August
    iranchembook.ir/edu iranchembook.ir/edu Volume 25 No. 8 August 2016 Managing Editor Corporate Office: Mahabir Singh Plot 99, Sector 44 Institutional area, Gurgaon -122 003 (HR). Editor Tel : 0124-6601200 e-mail : [email protected] website : www.mtg.in Anil Ahlawat Regd. Office: (BE, MBA) 406, Taj Apartment, Near Safdarjung Hospital, New Delhi - 110029. Class 11 NEET | JEE Essentials 8 Examiner’s Mind 20 You Ask, We Answer 29 Ace Your Way CBSE 31 MPP-2 39 Concept Map 46 Class 12 NEET | JEE Essentials 43 Concept Map 47 Examiner’s Mind 57 Ace Your Way CBSE 66 MPP-2 72 Competition Edge Advanced Chemistry Bloc 75 WB JEE Solved Paper 2016 77 Chemistry Musing Problem Set 37 82 Chemistry Musing Solution Set 36 84 CONTENTS Crossword 85 Subscribe online at www.mtg.in Individual Subscription Rates Combined Subscription Rates 1 yr. 2 yrs. 3 yrs. 1 yr. 2 yrs. 3 yrs. Mathematics Today 330 600 775 PCM 900 1500 1900 Chemistry Today 330 600 775 PCB 900 1500 1900 Physics For You 330 600 775 PCMB 1000 1800 2300 Biology Today 330 600 775 Send D.D/M.O in favour of MTG Learning Media (P) Ltd. Payments should be made directly to : MTG Learning Media (P) Ltd, Plot No. 99, Sector 44, Gurgaon - 122003 (Haryana) We have not appointed any subscription agent. Owned, Printed and Published by Mahabir Singh from 406, Taj Apartment, New Delhi - 29 and printed by Personal Graphics and Advertisers (P) Ltd., Okhla Industrial Area, Phase-II, New Delhi. Readers are adviced to make appropriate thorough enquiries before acting upon any advertisements published in this magazine.
    [Show full text]
  • Bond-Selective and Surface-Site-Specific Dissociation of Methane on Platinum
    Bond-selective and surface-site-specific dissociation of methane on platinum Thèse N° 9530 Présentée le 31 mai 2019 à la Faculté des sciences de base Laboratoire de chimie physique moléculaire Programme doctoral en chimie et génie chimique pour l’obtention du grade de Docteur ès Sciences par Ana GUTIÉRREZ GONZÁLEZ Acceptée sur proposition du jury Prof. J.-E. Moser, président du jury Prof. R. Beck, directeur de thèse Dr L. Juurlink, rapporteur Prof. D. J. Auerbach, rapporteur Dr M. Lingenfelder, rapporteuse 2019 To my parents and Marta, for their daily words of encouragement over these four years. To Julio, for joining this adventure and being always by my side. Abstract I present a molecular beam study of methane dissociation on different surface sites of several platinum single crystal surfaces (Pt(111), Pt(211), Pt(210), Pt(110)-(2x1)). The experiments were performed in a molecular beam/surface-science apparatus that combines rovibrational state-selective excitation of reactants with detection of the reaction products by reflection ab- sorption infrared spectroscopy (RAIRS), Auger electron spectroscopy (AES) and King and Wells (K&W) technique. First, I explore how the barrier for methane dissociation depends on the Pt surface site (terrace, step, kink, and ridge atoms). For that, I compare the av- erage reaction probabilities of methane on the different crystals using K&W. Moreover, I used the site-specific detection of chemisorbed methyl species by RAIRS to obtain the site-specific reactivity on steps, ridges and terraces. The highest methane reactivity and therefore the lowest barrier was observed for the surface atoms with the lowest coordination.
    [Show full text]