Engineering Chemistry
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Atomic Orbitals
Visualization of Atomic Orbitals Source: Robert R. Gotwals, Jr., Department of Chemistry, North Carolina School of Science and Mathematics, Durham, NC, 27705. Email: [email protected]. Copyright ©2007, all rights reserved, permission to use for non-commercial educational purposes is granted. Introductory Readings Where are the electrons in an atom? There are a number of Models - a description of models that look to describe the location and behavior of some physical object or electrons in atoms. It is important to know this information, as behavior in nature. Models it helps chemists to make statements and predictions about are often mathematical, describing the behavior of how atoms will react with other atoms to form molecules. The some event. model one chooses will oftentimes influence the types of statements one can make about the behavior – that is, the reactivity – of an atom or group of atoms. Bohr model - states that no One model, the Bohr model, describes electrons as small two electrons in an atom can billiard balls, rotating around the positively charged nucleus, have the same set of four much in the way that planets quantum numbers. orbit around the Sun. The placement and motion of electrons are found in fixed and quantifiable levels called orbits, Orbits- where electrons are or, in older terminology, shells. believed to be located in the There are specific numbers of Bohr model. Orbits have a electrons that can be found in fixed amount of energy, and are identified with the each orbit – 2 for the first orbit, principle quantum number 8 for the second, and so forth. -
Predicting Experimentally Stable Allotropes: Instability of Penta-Graphene
Predicting experimentally stable allotropes: Instability of penta-graphene Christopher P. Ewelsa,1, Xavier Rocquefelteb, Harold W. Krotoc,1, Mark J. Raysond,e, Patrick R. Briddone, and Malcolm I. Heggied aInstitut des Matériaux Jean Rouxel, CNRS UMR 6502, Université de Nantes, 44322 Nantes, France; bInstitut des Sciences Chimiques de Rennes, UMR 6226 CNRS, Université de Rennes 1, 35042 Rennes, France; cDepartment of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306; dDepartment of Chemistry, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom; and eSchool of Electrical and Electronic Engineering, University of Newcastle, Newcastle upon Tyne NE1 7RU, United Kingdom Contributed by Harold W. Kroto, October 14, 2015 (sent for review September 25, 2015; reviewed by Peter John Frederick Harris and Humberto Terrones) In recent years, a plethora of theoretical carbon allotropes have been Results and Discussion proposed, none of which has been experimentally isolated. We Thermodynamic Stability: Relative Energy. The first test of any new discuss here criteria that should be met for a new phase to be poten- proposed structure is of its thermodynamic stability. Considering tially experimentally viable. We take as examples Haeckelites, 2D penta-graphene, although real phonon energies (positive eigen- 2 networks of sp -carbon–containing pentagons and heptagons, and values from the Hessian matrix) indicate that it is at least a local “penta-graphene,” consisting of a layer of pentagons constructed structural minimum (4), its formation enthalpy shows that it is a 2 3 from a mixture of sp -andsp -coordinated carbon atoms. In 2D pro- very high-energy structure. We have performed a number of calcu- jection appearing as the “Cairo pattern,” penta-graphene is elegant lations on penta-graphene and structural derivatives, using density and aesthetically pleasing. -
Mixtures Comment on What You Observe in This Photograph
Elements Compounds Mixtures Comment on what you observe in this photograph. How do the sweets in this photograph model the idea of elements, compounds and mixtures? Elements, Compounds & Mixtures By the end of this topic students should be able to… • Identify elements, compounds and mixtures. • Define and explain the terms element, compound and mixture. • Give examples of elements, compounds and mixtures. • Describe the similarities and differences between elements, compounds and mixtures. Elements, Compounds & Mixtures How can I classify the different materials in the world around me? Elements, Compounds & Mixtures Elements, Compounds & Mixtures Elements, Compounds & Mixtures Elements, Compounds & Mixtures Elements, Compounds & Mixtures Elements, Compounds & Mixtures • What other classification systems do scientists use? • One example is the classification of plants and animals in biology. Elements, Compounds & Mixtures Could I have a brief introduction to elements, compounds and mixtures? Elements, Compounds & Mixtures • Iron and sulfur are both chemical elements. • A mixture of iron and sulfur can be separated by a magnet because iron can be magnetised but sulfur cannot. Elements, Compounds & Mixtures Duration 10 seconds. Duration • Iron and sulfur are both chemical elements. • A mixture of iron and sulfur can be separated by a magnet because iron can be magnetised but sulfur cannot. Elements, Compounds & Mixtures • Iron and sulfur react to form the compound iron(II) sulfide. • The compound iron(II) sulfide has new properties that are different to those of iron and sulfur, e.g. iron(II) sulfide is not attracted towards a magnet. Elements, Compounds & Mixtures Duration Duration 25 seconds. • Iron and sulfur react to form the compound iron(II) sulfide. -
Chemical Bonding & Chemical Structure
Chemistry 201 – 2009 Chapter 1, Page 1 Chapter 1 – Chemical Bonding & Chemical Structure ings from inside your textbook because I normally ex- Getting Started pect you to read the entire chapter. 4. Finally, there will often be a Supplement that con- If you’ve downloaded this guide, it means you’re getting tains comments on material that I have found espe- serious about studying. So do you already have an idea cially tricky. Material that I expect you to memorize about how you’re going to study? will also be placed here. Maybe you thought you would read all of chapter 1 and then try the homework? That sounds good. Or maybe you Checklist thought you’d read a little bit, then do some problems from the book, and just keep switching back and forth? That When you have finished studying Chapter 1, you should be sounds really good. Or … maybe you thought you would able to:1 go through the chapter and make a list of all of the impor- tant technical terms in bold? That might be good too. 1. State the number of valence electrons on the following atoms: H, Li, Na, K, Mg, B, Al, C, Si, N, P, O, S, F, So what point am I trying to make here? Simply this – you Cl, Br, I should do whatever you think will work. Try something. Do something. Anything you do will help. 2. Draw and interpret Lewis structures Are some things better to do than others? Of course! But a. Use bond lengths to predict bond orders, and vice figuring out which study methods work well and which versa ones don’t will take time. -
Electron Configurations, Orbital Notation and Quantum Numbers
5 Electron Configurations, Orbital Notation and Quantum Numbers Electron Configurations, Orbital Notation and Quantum Numbers Understanding Electron Arrangement and Oxidation States Chemical properties depend on the number and arrangement of electrons in an atom. Usually, only the valence or outermost electrons are involved in chemical reactions. The electron cloud is compartmentalized. We model this compartmentalization through the use of electron configurations and orbital notations. The compartmentalization is as follows, energy levels have sublevels which have orbitals within them. We can use an apartment building as an analogy. The atom is the building, the floors of the apartment building are the energy levels, the apartments on a given floor are the orbitals and electrons reside inside the orbitals. There are two governing rules to consider when assigning electron configurations and orbital notations. Along with these rules, you must remember electrons are lazy and they hate each other, they will fill the lowest energy states first AND electrons repel each other since like charges repel. Rule 1: The Pauli Exclusion Principle In 1925, Wolfgang Pauli stated: No two electrons in an atom can have the same set of four quantum numbers. This means no atomic orbital can contain more than TWO electrons and the electrons must be of opposite spin if they are to form a pair within an orbital. Rule 2: Hunds Rule The most stable arrangement of electrons is one with the maximum number of unpaired electrons. It minimizes electron-electron repulsions and stabilizes the atom. Here is an analogy. In large families with several children, it is a luxury for each child to have their own room. -
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%FQBSUNFOUPG"QQMJFE1IZTJDT " BM #') ŗ U P % % ŗ 3,)!(ŗ " 0#& <#( #(.,.#)(ŗ1#."ŗ (ŗ ,)(ŗ 3,) ! (ŗ#(. (()-.,/./,-ŗ , . #) (ŗ1 5JNP7FIWJM»JOFO #. " ŗ ,) (ŗ(() -. ,/ . /, -ŗ 9HSTFMG*aeegjj+ 9HSTFMG*aeegjj+ *4#/ #64*/&44 *4#/ QEG &$0/0.: *44/- *44/ "35 *44/ QEG %&4*(/ "3$)*5&$563& " B "BMUP6OJWFSTJUZ M U 4DIPPMPG4DJFODF 4$*&/$& P %FQBSUNFOUPG"QQMJFE1IZTJDT 5&$)/0-0(: 6 XXXBBMUPGJ OJ W $304407&3 F S T %0$503"- J %0$503"- U %*44&35"5*0/4 Z %*44&35"5*0/4 Aalto University publication series DOCTORAL DISSERTATIONS 5/2012 Hydrogen interaction with carbon nanostructures Timo Vehviläinen Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the School of Science for public examination and debate in Auditorium K at the Aalto University School of Science (Espoo, Finland) on the 19th of January 2012 at 13 o’clock. Aalto University School of Science Department of Applied Physics Electronic Properties of Materials Supervisor Prof. Risto Nieminen Instructor Dr. Maria Ganchenkova Preliminary examiners Prof. Tapani Pakkanen, University of Eastern Finland Prof. Gotthard Seifert, Technische Universität Dresden Opponent Prof. Kim Bolton, University of Borås Aalto University publication series DOCTORAL DISSERTATIONS 5/2012 © Timo Vehviläinen ISBN 978-952-60-4469-9 (printed) ISBN 978-952-60-4470-5 (pdf) ISSN-L 1799-4934 ISSN 1799-4934 (printed) ISSN 1799-4942 (pdf) Unigrafia Oy Helsinki 2012 Finland The dissertation can be read at http://lib.tkk.fi/Diss/ Publication orders (printed -
Instability of Penta-Graphene
Predicting experimentally stable allotropes: Instability of penta-graphene Christopher P. Ewelsa,1, Xavier Rocquefelteb, Harold W. Krotoc,1, Mark J. Raysond,e, Patrick R. Briddone, and Malcolm I. Heggied aInstitut des Matériaux Jean Rouxel, CNRS UMR 6502, Université de Nantes, 44322 Nantes, France; bInstitut des Sciences Chimiques de Rennes, UMR 6226 CNRS, Université de Rennes 1, 35042 Rennes, France; cDepartment of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306; dDepartment of Chemistry, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom; and eSchool of Electrical and Electronic Engineering, University of Newcastle, Newcastle upon Tyne NE1 7RU, United Kingdom Contributed by Harold W. Kroto, October 14, 2015 (sent for review September 25, 2015; reviewed by Peter John Frederick Harris and Humberto Terrones) In recent years, a plethora of theoretical carbon allotropes have been Results and Discussion proposed, none of which has been experimentally isolated. We Thermodynamic Stability: Relative Energy. The first test of any new discuss here criteria that should be met for a new phase to be poten- proposed structure is of its thermodynamic stability. Considering tially experimentally viable. We take as examples Haeckelites, 2D penta-graphene, although real phonon energies (positive eigen- 2 networks of sp -carbon–containing pentagons and heptagons, and values from the Hessian matrix) indicate that it is at least a local “penta-graphene,” consisting of a layer of pentagons constructed structural minimum (4), its formation enthalpy shows that it is a 2 3 from a mixture of sp -andsp -coordinated carbon atoms. In 2D pro- very high-energy structure. We have performed a number of calcu- jection appearing as the “Cairo pattern,” penta-graphene is elegant lations on penta-graphene and structural derivatives, using density and aesthetically pleasing. -
Lecture 3. the Origin of the Atomic Orbital: Where the Electrons Are
LECTURE 3. THE ORIGIN OF THE ATOMIC ORBITAL: WHERE THE ELECTRONS ARE In one sentence I will tell you the most important idea in this lecture: Wave equation solutions generate atomic orbitals that define the electron distribution around an atom. To start we need to simplify the math by switching to spherical polar coordinates (everything = spherical) rather than Cartesian coordinates (everything = at right angles). So the wave equations generated will now be of the form ψ(r, θ, Φ) = R(r)Y(θ, Φ) where R(r) describes how far out on a radial trajectory from the nucleus you are. r is a little way out and is small Now that we are extended radially on ψ, we need to ask where we are on the sphere carved out by R(r). Think of blowing up a balloon and asking what is going on at the surface of each new R(r). To cover the entire surface at projection R(r), we need two angles θ, Φ that get us around the sphere in a manner similar to knowing the latitude & longitude on the earth. These two angles yield Y(θ, Φ) which is the angular wave function A first solution: generating the 1s orbit So what answers did Schrodinger get for ψ(r, θ, Φ)? It depended on the four quantum numbers that bounded the system n, l, ml and ms. So when n = 1 and = the solution he calculated was: 1/2 -Zr/a0 1/2 R(r) = 2(Z/a0) *e and Y(θ, Φ) = (1/4π) . -
Photoionization of Kcs Molecule: Origin of the Structured Continuum?
atoms Article Photoionization of KCs Molecule: Origin of the Structured Continuum? Goran Pichler 1,*, Robert Beuc 1, Jahja Kokaj 2, David Sarkisyan 3, Nimmy Jose 2 and Joseph Mathew 2 1 Institute of Physics, 10000 Zagreb, Croatia; [email protected] 2 Department of Physics, Kuwait University, P.O. Box 5969, Safat 13060, Kuwait; [email protected] (J.K.); [email protected] (N.J.); [email protected] (J.M.) 3 Institute for Physical Research, Armenian Academy of Science, Ashtarak 0203, Armenia; [email protected] * Correspondence: [email protected]; Tel.: +385-91-469-8826 Received: 30 April 2020; Accepted: 26 May 2020; Published: 28 May 2020 Abstract: We report the experimental observation of photoionization bands of the KCs molecule in the deep ultraviolet spectral region between 200 and 420 nm. We discuss the origin of observed photoionization bands as stemming from the absorption from the ground state of the KCs molecule to the excited states of KCs+ molecule for which we used existing potential curves of the KCs+ molecule. An alternative explanation relies on the absorption from the ground state of the KCs molecule to the doubly excited states of the KCs** molecule, situated above the lowest molecular state of KCs+. The relevant potential curves of KCs** are not known yet, but all those KCs** potential curves are certainly autoionizing. However, these two photoionization pathways may interfere resulting in a special interference structured continuum, which is observed as complex bands. Keywords: photoionization; alkali molecule; autoionization of molecule; heteronuclear molecule 1. Introduction High-temperature alkali mixtures possessing high densities of constituents enable observation of the characteristic bands of mixed alkali molecules [1]. -
Nanomaterials Introduction Nanomaterials•Top-Down Science •Bottom-Up Science
nanomaterials introduction Nanomaterials•Top-down Science •Bottom-up Science What are nanomaterials? Nanomaterials are materials are materials possessing grain sizes on the order of a billionth of a meter.(10 -9 M) A material in which at least one side is between 1 and 1000 nm. Nanomaterial research literally exploded in mid -1980’s Some slides by Maya Bhatt history • Big bang • Fires • 1950- fused silica • Why such a buzz word today? Examples • Several biological materials are nanomaterials- bone, hair, wing scales on a butterfly etc. • Viruses are nanomaterials • Clays • Pigments • Volcanic ash Engineered nanomaterials (ENM or EN) Materials manufactured for their properties • Sunscreens • Paints • Cosmetics • Fillers • Catalysts INCIDENTAL: ultrafine airborne particles NATURAL • Conventional materials have grain size anywhere from 100 µm to 1mm and more • Particles with size between 1-100(0) nm are normally regarded as Nanomaterials • The average size of an atom is in the order of 1-2 Angstroms in radius. • 1 nanometer =10 Angstroms • 1 nm there may be 3-5 atoms Two principal factors cause the properties of nanomaterials to differ significantly from Bulk materials: • Increased relative surface area: a greater amount of the material comes into contact with surrounding materials and increases reactivity • Quantum effects. These factors can change or enhance properties such as reactivity, strength and electrical characteristics. Surface Effects • As a particle decreases in size, a greater proportion of atoms are found at the surface compared to those inside. For example, a particle of • Size-30 nm-> 5% of its atoms on its surface • Size-10 nm->20% of its atoms on its surface • Size-3 nm-> 50% of its atoms on its surface • Nanoparticals are more reactive than large particles (Catalyst) Quantum Effects Quantum confinement The quantum confinement effect can be observed once the diameter of the particle is of the same magnitude as the wavelength of the electron Wave function. -
NOTICE: This Is the Author's Version of a Work That Was Accepted For
NOTICE: this is the author’s version of a work that was accepted for publication in Carbon. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Carbon [VOL 50, ISSUE 3, March 2012] DOI 10.1016/j.carbon.2011.11.002 GUEST EDITORIAL Nomenclature of sp2 carbon nanoforms Carbon’s versatile bonding has resulted in the discovery of a bewildering variety of nanoforms which urgently need a systematic and standard nomenclature [1]. Besides fullerenes, nanotubes and graphene, research teams around the globe now produce a plethora of carbon-based nanoforms such as ‘bamboo’ tubes, ‘herringbone’ and ‘bell’ structures. Each discovery duly gains a new, sometimes whimsical, name, often with its discoverer unaware that the same nanoform has already been reported several times but with different names (for example the nanoform in Figure 1i is in different publications referred to as ‘bamboo’ [2], ‘herringbone-bamboo’ [3], ‘stacked-cups’ [4] and ‘stacked-cones’ [5]). In addition, a single name is often used to refer to completely different carbon nanoforms (for example, the ‘bamboo’ structure in [2] is notably different from ‘bamboo’ in Ref [6]). The result is a confusing overabundance of names which makes literature searches and an objective comparison of results extremely difficult, if not impossible. There have been several attempts to bring order to the chaos of carbon nomenclature. An IUPAC subcommittee on carbon terminology and characterization that ran until 1991 produced a glossary of 114 terms for carbon materials. -
Atomic Structure
1 Atomic Structure 1 2 Atomic structure 1-1 Source 1-1 The experimental arrangement for Ruther- ford's measurement of the scattering of α particles by very thin gold foils. The source of the α particles was radioactive radium, a rays encased in a lead block that protects the surroundings from radiation and confines the α particles to a beam. The gold foil used was about 6 × 10-5 cm thick. Most of the α particles passed through the gold leaf with little or no deflection, a. A few were deflected at wide angles, b, and occasionally a particle rebounded from the foil, c, and was Gold detected by a screen or counter placed on leaf Screen the same side of the foil as the source. The concept that molecules consist of atoms bonded together in definite patterns was well established by 1860. shortly thereafter, the recognition that the bonding properties of the elements are periodic led to widespread speculation concerning the internal structure of atoms themselves. The first real break- through in the formulation of atomic structural models followed the discovery, about 1900, that atoms contain electrically charged particles—negative electrons and positive protons. From charge-to-mass ratio measurements J. J. Thomson realized that most of the mass of the atom could be accounted for by the positive (proton) portion. He proposed a jellylike atom with the small, negative electrons imbedded in the relatively large proton mass. But in 1906-1909, a series of experiments directed by Ernest Rutherford, a New Zealand physicist working in Manchester, England, provided an entirely different picture of the atom.