DOCSLIB.ORG

Recent Developments in Chalcogen Chemistry

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Recent Developments in Chalcogen Chemistry RECENT DEVELOPMENTS IN CHALCOGEN CHEMISTRY Tristram Chivers Department of Chemistry, University of Calgary, Calgary, Alberta, Canada WHERE IS CALGARY? Lecture 1: Background / Introduction Outline • Chalcogens (O, S, Se, Te, Po) • Elemental Forms: Allotropes • Uses • Trends in Atomic Properties • Spin-active Nuclei; NMR Spectra • Halides as Reagents • Cation Formation and Stabilisation • Anions: Structures • Solutions of Chalcogens in Ionic Liquids • Oxides and Imides: Multiple Bonding 3 Elemental Forms: Sulfur Allotropes Sulfur S6 S7 S8 S10 S12 S20 4 Elemental Forms: Selenium and Tellurium Allotropes Selenium • Grey form - thermodynamically stable: helical structure cf. plastic sulfur. R. Keller, et al., Phys. Rev. B. 1977, 4404. • Red form - cyclic Cyclo-Se8 (cyclo-Se7 and -Se6 also known). Tellurium • Silvery-white, metallic lustre; helical structure, cf. grey Se. • Cyclic allotropes only known entrapped in solid-state structures e.g. Ru(Ten)Cl3 (n = 6, 8, 9) M. Ruck, Chem. Eur. J. 2011, 17, 6382 5 Uses – Sulfur Sulfur : Occurs naturally in underground deposits. • Recovered by Frasch process (superheated water). • H2S in sour gas (> 70%): Recovered by Klaus process: Klaus Process: 2 H S + SO 3/8 S + 2 H O 2 2 8 2 • Primary industrial use (70 %): H2SO4 in phosphate fertilizers 6 Uses – Selenium and Tellurium Selenium and Tellurium : Recovered during the refining of copper sulfide ores Selenium: • Photoreceptive properties – used in photocopiers (As2Se3) • Imparts red color in glasses Tellurium: • As an alloy with Cu, Fe, Pb and to harden steel • Toxicity! Formation of Me2Te 7 Specialised Uses of Metal Tellurides Solar energy • Silicon and GaAs are widely used • Other promising materials: CdTe – Band gap 1.49 eV • Major manufacturer of CdTe solar cells: First Solar (Phoenix, USA) • CdTe technology expected to increase tenfold over the next 10 years • Limitation: Very low natural abundance of Te (1-5 ppb) Thermoelectric Generators • Sb2Te 3, PbTe exhibit thermoelectric properties – band gaps ~ 0.21 eV • Low efficiency – use limited to solid-state refrigeration: e.g. Bi2Te 3 in portable food coolers • Improved efficiency could lead to applications in the conversion of waste heat from nuclear reactors and industrial equipment Ibers, Nature Chemistry, 2009, 1, 508. 8 Trends in Atomic Properties S Se Te Covalent Radius (Å) 1.03 1.17 1.35 van der Waals Radius 1.80 1.90 2.06 Electronegativity 2.6 2.6 2.1 First Ionization Potential 999.6 941.0 869.3 (kJ mol-1) D(E-E) (kJ mol-1) 266 192 137 • Steady increase in size S • Electronegativity decrease only between Se and Te • Heavy chalcogens more easily oxidized • Heavy chalcogens form much weaker homoatomic bonds 9 Binary Chalcogen Halides Monohalides, E2Cl2 • E = S, Se: Commercially available • E = Te: Dark brown, thermally unstable liquid Cp2TiSe5 Li2Te + TeCl4 Te 2Cl2 1,2-Te 2Se5 Laitinen, Chem. Commun, 1998, 2381. Dihalides, ECl2 • E = S: Readily disproportionates to S2Cl2 • E = Se: Disproportionates to Se2Cl2 and SeCl4 • E = Te: Unstable, but forms stable adducts e.g. TeCl2·tmtu (tmtu = tetramethylthiourea) Tetrahalides, ECl4 • E = S: Thermally unstable • E = Se, Te: Commercially available white solids 10 Spin Active Nuclei - NMR Spectra Nucleus Spin (I) Abundance (%) 33S 3/2 0.76 77Se 1/2 7.58 (123Te) 1/2 0.87 125Te 1/2 6.99 Et3P=Te 31P NMR 125Te NMR † † * * † = 125Te satellites * = 123Te satellites 20 0 -20 -850 -900 -950 11 Reactions of Selenium Dichloride Synthesis: Se + SO2Cl2 THF SeCl2 O 77 • Stable for 1 day at 23 C ( Se NMR: Disproportionates to Se2Cl2 + SeCl4) Chivers, Laitinen, Inorg. Chem. 1999, 38, 4093. MeO OMe MeO Cl Se Cl R SeCl 2 Se (1) (3) R R MeO (2) NH2 SeCl Se N N + N N + Se Se SeCl Se Se Cl Cl N N Se (1) Potapov, et al., Tetrahedron Letters, 2010, 51, 89; 2009, 50, 306. (2) Chivers, Laitinen, Chem Commun. 2000, 759. (3) Bendokov, et al., J. Am. Chem. Soc., 2008, 130, 6734. 12 Stabilization of Heavy Chalcogen Dihalides Tetramethylthiourea (tmtu) complexes TeO2 + HClaq + tmtu TeCl2·(tmtu)n (n = 1,2) L . Cl N Te. L = S Cl L N Foss, Acta Chem. Scand., 1986, A40, 675. Bipyridyl complexes • Thermally stable • Metathesis with RMgX (R = Ph, Bz) gives R2E (E = Se, Te) E = Se, X = Cl, Br; E = Te, X = Cl Ragogna, Chem. Eur. J. 2009, 39, 10263. 13 Trialkylphosphine Adducts of TeCl2 Et3P=Te + SO2Cl2 (or I2) Et3PTeX2 (X = Cl, I) + SO2 Et3PTeCl2 + Me3SiBr Et3PTeBr2 Cl Te X d(Te-P) (Å) δ (125Te) (ppm) 1J(P-Te) (Hz) Cl 2.466(1) 766 1395 Br 2.473(1) 627 1312 I 2.490(1) 331 1248 J. Konu and T. Chivers, Dalton Trans., 2006, 3941. 14 Ligand-Stabilized Chalcogen Dications Electron-donor ligands, e.g. diazabutadiene (DAB) (26a,b) or N-heterocyclic carbenes (NHC) (26c) stabilize highly electrophilic chalcogen dications E = S, Se S, Se: Ragogna, ACIE, 2009, 48, 2210. Te: Ragogna, ACIE, 2009, 48, 4409. 15 2+ DAB Complexes as Se Transfer Agents Se2+ complexes: - - Preparation and ligand exchange reactions (NB: CF3SO3 (OTf ) anions) Cy = cyclohexyl Activation of small molecules by Se2+? Ragogna, Chem Commun., 2010, 46, 1041. 16 Anions: Polysulfides Dianions 2- • Unbranched chains Sx (x = 2-8) + + + • Stabilized by large cations (Cs , Na(15-crown-5)] , [PPh4] ) 2- e.g. two distinct geometries of S7 : all-trans (++++) trans-cis-trans (++--) M. G. Kanatzidis, et al. Inorg. Chem. 1983, 22, 290. C. Müller, P. Böttcher, Z. Naturforsch. B, 1995, 50, 1623. Radical Anions –• • Formation of the blue trisulfur radical anion S3 (λmax ~ 620 nm) is a common feature of solutions of polysulfides . Chivers, Inorg. Chem. 1972, 11, 2515. “Ubiquitous Trisulfur Radical Anion” Chivers, Nature, 1974, 252, 32. 17 –• The Stable Radical Anion Cyclo-S6 + • Isolated as [PPh4] salt • Two long S···S bonds (2.633 Å) • MO analysis and EPR spectra •• –• indicate 2 fragments, S3 and S3 • Electron-pair bond between 2b1 SOMOs of both fragments • 3-electron bond between 1a2 of the biradical and 1a2 of the radical Cyclo-S – • Cyclo-S anion 6 6 K. Dehnicke, Angew. Chem. Int. Ed. 2000, 39, 4580 • Cyclo-S6 has one fewer electron 18 Anions: Polyselenides and Polytellurides Polyselenides 2- • Chain structures Sex (x = 2-8) 2- • Se also forms bicyclic and spirocyclic dianions Sex (x = 10, 11) • 3- and 4-coordinate Se atoms participate in 3-centre 2e- bonding 2- 2- Se10 Se11 D. Fenske, Angew. Chem. 1990, 29, 390. B. Krebs, Z. Anorg. Allg. Chem., 1991, 592, 17. Polytellurides • Charges either less or greater than 2- may be observed, 3- e.g. [Te6 ] in Cs3Te22 • Hypervalent Bonding σ* • Intra- and inter-molecular np2 σ* bonding 2 np 19 Solutions of Chalcogens in Ionic Liquids The Chalcogens as Reagents Sulfur: Poor solubility in CCl4, pyridine and toluene; dissolves well in CS2 Selenium: Slightly soluble in CS2 Tellurium: In ethylenediamine → Nanotubes of Te and Se J. Lu, et al., J. Mat. Chem. 2002, 12, 2755. Carbon Disulfide: Neurotoxic, highly flammable, reactive solvent Ionic Liquids • Safe alternative to CS2 for dissolving sulfur O • At 100 -155 C S8 has very high solubility i • In [P Bu3Me][OTs] sulfur forms bright blue solutions → carmine red at higher concentrations Identity of sulfur species in these solutions? Seddon, Chem. Commun. 2010, 46, 716. 20 The Trisulfur Radical Ion in Ionic Liquids • UV-Vis spectrum shows an isosbestic point • Dilute solutions are blue (617 nm) and concentrated solutions are red • Equilibrium between hexasulfide and trisulfur radical anion 2- -• S6 2 S3 •- S3 is the chromophore in lapis lazuli and ultramarine blue 21 •- Sensor Material Based on Occluded S3 Univalent Zinc, Zn+ Paramagnetic Zn+ incorporated into zeolite by reaction of Zn vapor (at 450 OC) with protons of two Brønsted acid sites → Zn@SAPO (Si Al Phosphate) o Sulfur vapour at 280 C introduced into Zn@SAPO cage and S3 is trapped in the cavity and then reacts with Zn+ to produce blue S •- 3 Li and Chen, JACS, 2003, 125, 6622; J. Mater. Chem., 2010, 20, 3307. 22 •- Occluded S3 as a Sensor for Water Sensoring Mechanism •- • Occluded S3 is a sensitive detector for H2O in air or organic solvents •- •- S3 + H2O S3 + H2O • Monitored by visible and EPR spectroscopy Colorimetric cards estimate ppm water based on amount of sensor material used (3.0, 6.3, 9.0 mg) 23 Solutions of Se and Te in Ionic Liquids • Se and Te also dissolve in ionic liquids at elevated temps to give orange (Se at 50 oC) and purple (Te at 170 OC) solutions •- • Orange colour may be Se3 ; identity of purple species unknown • Reactivity of chalcogen solutions in ionic liquids demonstrated by reactions with PPh3 to give Ph3PE ( E = Se, Te) 24 Binary Chalcogen Dioxides: Multiple Bonding Sulfur Dioxide • A monomeric gaseous molecule • S=O double bonds – bent structure C2v Selenium and Tellurium Oxides • White solids with polymeric structures • (SeO2)n : 2-D polymer – Both Se–O and Se=O bonds • (TeO2)n : 3-D polymer - Only Te–O single bonds O S O O O O Se O Te n O O 25 Chalcogen Diimides - Structures Sulfur and Selenium Diimides • Monomeric: Cis, trans isomer usually preferred R E E N N N N R E R N N R R R (cis, cis) (cis, trans) (trans, trans) E = Se, R = Ad: T. Maaninen, R. Laitinen, T. Chivers, Chem Commun. 2002, 1812. Tellurium Diimides • Dimeric: Two known conformations R R R R R N R R N N N N Te Te Te Te N N R N t n cis, endo, endo (R = Bu) trans, exo, exo (R = Oct, R’ = PPh2NSiMe3) Chivers, et al. JACS, 1995, 117, 2519; Inorg. Chem., 1996, 35, 9. 26 Chalcogen Diimides – Dimerization Energies (R = Me) E = S, Endothermic; E = Se, ~ Thermoneutral; E = Te, Exothermic Tuononen, Laitinen, Inorg.
Load more

Recommended publications
  • The Periodic Electronegativity Table
    The Periodic Electronegativity Table Jan C. A. Boeyens Unit for Advanced Study, University of Pretoria, South Africa Reprint requests to J. C. A. Boeyens. E-mail: [email protected] Z. Naturforsch. 2008, 63b, 199 – 209; received October 16, 2007 The origins and development of the electronegativity concept as an empirical construct are briefly examined, emphasizing the confusion that exists over the appropriate units in which to express this quantity. It is shown how to relate the most reliable of the empirical scales to the theoretical definition of electronegativity in terms of the quantum potential and ionization radius of the atomic valence state. The theory reflects not only the periodicity of the empirical scales, but also accounts for the related thermochemical data and serves as a basis for the calculation of interatomic interaction within molecules. The intuitive theory that relates electronegativity to the average of ionization energy and electron affinity is elucidated for the first time and used to estimate the electron affinities of those elements for which no experimental measurement is possible. Key words: Valence State, Quantum Potential, Ionization Radius Introduction electronegative elements used to be distinguished tra- ditionally [1]. Electronegativity, apart from being the most useful This theoretical notion, in one form or the other, has theoretical concept that guides the practising chemist, survived into the present, where, as will be shown, it is also the most bothersome to quantify from first prin- provides a precise definition of electronegativity. Elec- ciples. In historical context the concept developed in a tronegativity scales that fail to reflect the periodicity of natural way from the early distinction between antag- the L-M curve will be considered inappropriate.
    [Show full text]
  • Enhanced Heterogeneous Uptake of Sulfur Dioxide on Mineral Particles Through Modification of Iron Speciation During Simulated Cloud Processing
    Atmos. Chem. Phys., 19, 12569–12585, 2019 https://doi.org/10.5194/acp-19-12569-2019 © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License. Enhanced heterogeneous uptake of sulfur dioxide on mineral particles through modification of iron speciation during simulated cloud processing Zhenzhen Wang1, Tao Wang1, Hongbo Fu1,2,3, Liwu Zhang1, Mingjin Tang4, Christian George5, Vicki H. Grassian6, and Jianmin Chen1 1Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science & Engineering, Institute of Atmospheric Sciences, Fudan University, Shanghai, 200433, China 2Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China 3Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CICAEET), Nanjing University of Information Science and Technology, Nanjing 210044, China 4State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China 5University of Lyon, Université Claude Bernard Lyon 1, CNRS, IRCELYON, 69626, Villeurbanne, France 6Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA Correspondence: Hongbo Fu ([email protected]) and Jianmin Chen ([email protected]) Received: 7 May 2019 – Discussion started: 5 June 2019 Revised: 7 August 2019 – Accepted: 5 September 2019 – Published: 9 October
    [Show full text]
  • Removal of Heavy Metals from Aqueous Solution by Zeolite in Competitive Sorption System
    International Journal of Environmental Science and Development, Vol. 3, No. 4, August 2012 Removal of Heavy Metals from Aqueous Solution by Zeolite in Competitive Sorption System Sabry M. Shaheen, Aly S. Derbalah, and Farahat S. Moghanm rich volcanic rocks (tuff) with fresh water in playa lakes or Abstract—In this study, the sorption behaviour of natural by seawater [5]. (clinoptilolite) zeolites with respect to cadmium (Cd), copper The structures of zeolites consist of three-dimensional (Cu), nickel (Ni), lead (Pb) and zinc (Zn) has been studied in frameworks of SiO and AlO tetrahedra. The aluminum ion order to consider its application to purity metal finishing 4 4 wastewaters. The batch method has been employed, using is small enough to occupy the position in the center of the competitive sorption system with metal concentrations in tetrahedron of four oxygen atoms, and the isomorphous 4+ 3+ solution ranging from 50 to 300 mg/l. The percentage sorption replacement of Si by Al produces a negative charge in and distribution coefficients (Kd) were determined for the the lattice. The net negative charge is balanced by the sorption system as a function of metal concentration. In exchangeable cation (sodium, potassium, or calcium). These addition lability of the sorbed metals was estimated by DTPA cations are exchangeable with certain cations in solutions extraction following their sorption. The results showed that Freundlich model described satisfactorily sorption of all such as lead, cadmium, zinc, and manganese [6]. The fact metals. Zeolite sorbed around 32, 75, 28, 99, and 59 % of the that zeolite exchangeable ions are relatively innocuous added Cd, Cu, Ni, Pb and Zn metal concentrations (sodium, calcium, and potassium ions) makes them respectively.
    [Show full text]
  • ATOMIC RADII of the ELEMENTS References
    ATOMIC RADII OF THE ElEMENTS The simple model of an atom as a hard sphere that can approach The Cambridge Crystallographic Data Center also makes use only to a fixed distance from another atom to which it is not bond- of a set of “covalent radii” to determine which atoms in a crystal ed has proved useful in interpreting crystal structures and other are bonded to each other . Thus two atoms A and B are judged to molecular properties . The term van der Waals radius, rvdw, was be connected by a covalent bond if their separation falls within a originally introduced by Pauling as a measure of this atomic size . tolerance of ±0 .4 Å of the sum rcov (A) + rcov (B) . The covalent radii Thus in a closely packed structure two non-bonded atoms A and are given in the fourth column of the table . B will be separated by the sum of their van der Waals radii rvdw (A) and rvdw (B) . The set of van der Waals radii proposed by Pauling References was refined by Bondi (Reference 1) based on crystallographic data, gas kinetic collision cross sections, and liquid state properties . The 1 . Bondi, A ., J. Phys. Chem. 68, 441, 1964 . non-bonded contact distances predicted from the recommended 2 . Rowland, R . S . and Taylor, R ., J. Phys. Chem. 100, 7384, 1996 . 3 . Cambridge Crystallographic Data Center, www .ccdc .cam .ac .uk/prod- r of Bondi have been compared with actual data in the collec- vdw ucts/csd/radii/ tion of the Cambridge Crystallographic Data Center by Rowland and Taylor (Reference 2) and modified slightly .
    [Show full text]
  • Sulfur Safety Data Sheet SDS No: 6192 According to Federal Register / Vol
    Sulfur Safety Data Sheet SDS No: 6192 According To Federal Register / Vol. 77, No. 58 / Monday, March 26, 2012 / Rules And Regulations Revision Date: 10/23/2018 Date of Issue: 08/30/2012 Version: 1.0 SECTION 1: IDENTIFICATION 1.1. Product Identifier Product Form: Mixture Product Name: Sulfur Synonyms: Brimstone, Sulfur 1.2. Intended Use of the Product Hydrogen sulfide may be present in trace quantities (by weight) in molten sulfur but may accumulate to toxic or flammable concentrations in enclosed spaces such as molten sulfur storage pits, tanks, or tanker/railcar headspaces. Hydrogen sulfide is not considered a hazard associated with solid sulfur. 1.3. Name, Address, and Telephone of the Responsible Party Customer Hess Tower 1501 McKinney Houston, TX 77010 T:(713) 496-4000 When calling the main operator ask for the EHS Safety Department. All Hess SDSs are also available via the Hess.com website. 1.4. Emergency Telephone Number Emergency Number : (800) 424-9300 CHEMTREC (24 hours) SECTION 2: HAZARDS IDENTIFICATION 2.1. Classification of the Substance or Mixture GHS-US Classification Flam. Sol. 2 H228 Skin Irrit. 2 H315 Aquatic Acute 2 H401 Comb. Dust Full text of hazard classes and H-statements : see Section 16. 2.2. Label Elements GHS-US Labeling Hazard Pictograms (GHS-US) : GHS02 GHS07 Signal Word (GHS-US) : Warning Hazard Statements (GHS-US) : May form combustible dust concentrations in air. H228 - Flammable solid. H315 - Causes skin irritation. H401 - Toxic to aquatic life. Precautionary Statements (GHS-US) : P210 - Keep away from heat, sparks, open flames, hot surfaces. - No smoking. P240 - Ground/Bond container and receiving equipment.
    [Show full text]
  • On the Cycling of Sulfur and Mercury in the St. Louis River Watershed, Northeastern Minnesota
    Page 1 of 91 Final Report On the Cycling of Sulfur and Mercury in the St. Louis River Watershed, Northeastern Minnesota An Environmental and Natural Trust Fund Final Report August 15, 2012 Michael Berndt and Travis Bavin Minnesota Department of Natural Resources 500 Lafayette Rd. St. Paul, MN 55455 Page 2 of 91 Final Report Contents Summary .......................................................................................................................................... 3 Introduction ..................................................................................................................................... 4 Methods ........................................................................................................................................... 5 Sampling Site Selection ................................................................................................................ 5 Chemical Analysis ......................................................................................................................... 6 34 18 Sulfur and Oxygen Isotopes in Dissolved Sulfate (δ SSO4 and δ OSO4)........................................ 7 Stream Gaging .............................................................................................................................. 7 Results .............................................................................................................................................. 7 Watershed Survey .......................................................................................................................
    [Show full text]
  • SO2 Removal by NH3 Gas Injection: Effects of Temperature and Moisture Content
    Ind. Eng. Chem. Res. 1994,33, 1231-1236 1231 SO2 Removal by NH3 Gas Injection: Effects of Temperature and Moisture Content Hsunling Bai' Institute of Environmental Engineering, National Chiao- Tung University, Hsin-Chu, Taiwan, R.O.C. Pratim Biswas and Tim C. Keener Department of Civil and Environmental Engineering, University of Cincinnati, Cincinnati, Ohio 45221 -0071 The removal of SO2 by NH3 gas injection at various temperatures and moisture contents has been studied experimentally. The product compositions of the NH3-SO2-HzO vapor reactions were also reported. A thermodynamic analysis was carried out to predict the SO2 removal as well as the product compositions. Both the experimental results and thermodynamic analysis indicated that SO2 removal and the product compositions are sensitive to the reaction temperature. Moisture content, once in large excess of the stoichiometric requirement, does not have a strong effect on the product compositions but plays an important role in the SO2 removal. Introduction conditions. Stromberger (1984) used X-ray diffraction and identified the product particles to be (NH&S04 Sulfur dioxide removal from flue gases is a goal of many crystals. air pollution engineers. Significant efforts in the develop- ment of new flue gas desulfurization (FGD) technologies Although a number of studies on the removal of SO2 are being made. Major processes related to FGD tech- from flue gases by NH3 injection have been conducted, nologies include water scrubbing, metal ion solutions, there is disagreement on the operating condition (such as catalytic oxidation, dry or semidry adsorption, wet lime temperature) that a high removal efficiency can be or limestone scrubbing, double alkali process, and ammonia obtained.
    [Show full text]
  • Sodium Chlorite Sulfur Destruction
    ® Basic Chemicals Sodium Chlorite Sulfur Destruction Application Description: Advantages of Sodium Chlorite/Chlorine Reduced sulfur compounds are a broad Dioxide: class of oxy-sulfur compounds, such as = = sulfite (SO3 ) and thiosulfate (S2O3 ), that Chlorine dioxide reacts the most rapidly have an oxidant demand. These and does not form chlorinated organic compounds are found in the waste streams by-products. of the petroleum, steel, paper and most While chlorine is the least expensive chemical industries. Their high oxidant chemical, it cannot be used when demand can cause eutrophication of natural organic compounds are present due to waters and excessive chlorine demand in the formation of chlorinated organic by- wastewaters treated by POTWs (Publicly products. Owned Treatment Works). When chlorine can't be used, hydrogen peroxide has the lowest chemical costs. Chlorine dioxide effectively oxidizes these species to sulfate ions over a broad pH range (5-9). Below a pH of 4, sodium Affected Industries: chlorite may be used without the generation Chemicals, Food, Iron & Steel, Mining, Oil of chlorine dioxide. Since these compounds Refining, Plastics & Rubber, Pulp & Paper, are usually found in mixtures of various Textiles ratios the required chlorine dioxide dosage must be determined for each application. Further Information More detailed information on sodium Alternatives: chlorite applications is available upon Hydrogen peroxide solution is added by request through the OxyChem Technical a chemical dosing pump. Services Department. Call or write to: Chlorine gas is added by a vacuum eductor system, while sodium OxyChem hypochlorite solution is added by a Technical Service Department chemical dosing pump. PO Box 12283 Wichita, Kansas 67277-2283 800-733-1165 Ext.
    [Show full text]
  • Atomic and Ionic Radii of Elements 1–96 Martinrahm,*[A] Roald Hoffmann,*[A] and N
    DOI:10.1002/chem.201602949 Full Paper & Elemental Radii Atomic and Ionic Radii of Elements 1–96 MartinRahm,*[a] Roald Hoffmann,*[a] and N. W. Ashcroft[b] Abstract: Atomic and cationic radii have been calculated for tive measureofthe sizes of non-interacting atoms, common- the first 96 elements, together with selected anionicradii. ly invoked in the rationalization of chemicalbonding, struc- The metric adopted is the average distance from the nucleus ture, and different properties. Remarkably,the atomic radii where the electron density falls to 0.001 electrons per bohr3, as defined in this way correlate well with van der Waals radii following earlier work by Boyd. Our radii are derived using derived from crystal structures. Arationalizationfor trends relativistic all-electron density functional theory calculations, and exceptionsinthose correlations is provided. close to the basis set limit. They offer asystematic quantita- Introduction cule,[2] but we prefer to follow through with aconsistent pic- ture, one of gauging the density in the atomic groundstate. What is the size of an atom or an ion?This question has been The attractivenessofdefining radii from the electron density anatural one to ask over the centurythat we have had good is that a) the electron density is, at least in principle, an experi- experimental metricinformation on atoms in every form of mental observable,and b) it is the electron density at the out- matter,and (more recently) reliable theory for thesesame ermost regionsofasystem that determines Pauli/exchange/ atoms. And the momentone asks this question one knows same-spinrepulsions, or attractive bondinginteractions, with that there is no unique answer.Anatom or ion coursing down achemical surrounding.
    [Show full text]
  • ARC: an Open-Source Library for Calculating Properties of Alkali Rydberg Atoms
    ARC: An open-source library for calculating properties of alkali Rydberg atoms N. Šibalic´a,∗, J. D. Pritchardb, C. S. Adamsa, K. J. Weatherilla aJoint Quantum Center (JQC) Durham-Newcastle, Department of Physics, Durham University, South Road, Durham, DH1 3LE, United Kingdom bDepartment of Physics, SUPA, University of Strathclyde, 107 Rottenrow East, Glasgow, G4 0NG, United Kingdom Abstract We present an object-oriented Python library for computation of properties of highly-excited Rydberg states of alkali atoms. These include single-body effects such as dipole matrix elements, excited-state lifetimes (radiative and black-body limited) and Stark maps of atoms in external electric fields, as well as two-atom interaction potentials accounting for dipole and quadrupole coupling effects valid at both long and short range for arbitrary placement of the atomic dipoles. The package is cross-referenced to precise measurements of atomic energy levels and features extensive documentation to facilitate rapid upgrade or expansion by users. This library has direct application in the field of quantum information and quantum optics which exploit the strong Rydberg dipolar interactions for two-qubit gates, robust atom-light interfaces and simulating quantum many-body physics, as well as the field of metrology using Rydberg atoms as precise microwave electrometers. Keywords: Alkali atom, Matrix elements, Dipole-dipole interactions, Stark shift, Förster resonances PROGRAM SUMMARY They are a flourishing field for quantum information process- Program Title: ARC: Alkali Rydberg Calculator ing [1, 2] and quantum optics [3, 4, 5] in the few to single exci- Licensing provisions: BSD-3-Clause tation regime, as well as many-body physics [6, 7, 8, 9, 10, 11], Programming language: Python 2.7 or 3.5, with C extension in the many-excitations limit.
    [Show full text]
  • Most Atoms Form Chemical Bonds to Obtain a Lower Potential Energy
    Integrated Chemistry <Kovscek> 6-1-2 Explain why most atoms form chemical bonds. Most atoms form chemical bonds to obtain a lower potential energy. Many share or transfer electrons to get a noble gas configuration. 6-1-3 Describe ionic and covalent bonding. Ions form to lower the reactivity of an atom. Ionic bonding is when the attraction between many cations and anions hold atoms together. Covalent bonding results from the sharing of electron pairs between two atoms. That is, when atoms share electrons, the mutual attraction between the electrons (electron clouds) and protons (the nucleus) hold the atoms together. 6-1-4 Explain why most chemical bonding is neither purely ionic nor purely covalent. In order for a bond to be totally ionic one atom would have to have an electronegativity of zero. (there aren’t any). To have a purely covalent bond the electronegativity must be equal. (Only the electronegativity of atoms of the same element are identical, diatomic elements are purely covalent) 6-1-5 Classify bonding type according to electronegativity differences. Differences in electronegativities reflect the character of bonding between elements. The electronegativity of the less- electronegative element is subtracted from that of the more- electronegative element. The greater the electronegativity difference, the more ionic is the bonding. Covalent Bonding happens between atoms with an electronegativity difference of 1.7 or less. That is the bond has an ionic character of 50% or less. Electronegativity % Ionic Character Covalent Differences Bond Type 0 to 0.3 0% to 5% Non - Polar Over 0.3 up to 1.7 5% to 50% Polar Over 1.7 Greater than 50 % Ionic Ionic Bonding occurs between atoms with an electronegativity difference of greater than 1.7.
    [Show full text]
  • ELECTRONEGATIVITY D Qkq F=
    ELECTRONEGATIVITY The electronegativity of an atom is the attracting power that the nucleus has for it’s own outer electrons and those of it’s neighbours i.e. how badly it wants electrons. An atom’s electronegativity is determined by Coulomb’s Law, which states, “ the size of the force is proportional to the size of the charges and inversely proportional to the square of the distance between them”. In symbols it is represented as: kq q F = 1 2 d 2 where: F = force (N) k = constant (dependent on the medium through which the force is acting) e.g. air q1 = charge on an electron (C) q2 = core charge (C) = no. of protons an outer electron sees = no. of protons – no. of inner shell electrons = main Group Number d = distance of electron from the nucleus (m) Examples of how to calculate the core charge: Sodium – Atomic number 11 Electron configuration 2.8.1 Core charge = 11 (no. of p+s) – 10 (no. of inner e-s) +1 (Group i) Chlorine – Atomic number 17 Electron configuration 2.8.7 Core charge = 17 (no. of p+s) – 10 (no. of inner e-s) +7 (Group vii) J:\Sciclunm\Resources\Year 11 Chemistry\Semester1\Notes\Atoms & The Periodic Table\Electronegativity.doc Neon holds onto its own electrons with a core charge of +8, but it can’t hold any more electrons in that shell. If it was to form bonds, the electron must go into the next shell where the core charge is zero. Group viii elements do not form any compounds under normal conditions and are therefore given no electronegativity values.
    [Show full text]