Showing papers on "Ionic bonding published in 1971"

SI Chemical Data

Abstract: Periodic Table Electronic Configuration of Elements References to Sources of Chemical Data International System of Units (SI) Fundamental Constants Conversion Factors Properties of the Elements, Conductivities, Radii, Structure Some Crystal Forms Properties of Inorganic Compounds Common Acid-Base Indicators Ionic Properties of Water: Specific Conductivity, Ionic Product Molar Conductivities at Infinite Dilution.

Ion binding by synthetic macrocyclic compounds.

Abstract: The existence of synthetic macrocyclic molecules with hydrophilic cavities containing multiple binding atoms and with hydrophobic exteriors gives rise to extraordinary possibilities with respect to the design and synthesis of molecules with specific cation and anion binding properties. The preparation of many new macrocyclic compounds has recently been reported, but few practical applications for them have been suggested. From the information available, it is becoming clear that it should be possible to synthesize macrocycles that will have specified, or selected, ion binding properties. Cavity size can be varied to accommodate only those cations or anions within a specified narrow band of sizes. Numbers and types of coordinating atoms can be chosen to give essentially electrostatic or covalent bonding or a combination of the two in a metalmacrocycle complex. The metal ligand bond appears to be predominantly ionic in the case of the cyclic polyethers but the covalent character increases on substitution of sulfur or nitrogen for oxygen donor atoms. The essential hydrophobic exteriors of the macrocycles can be modified by the addition of side chains and groups to facilitate the solution of anions and cations in organic solvents. The structures of many macrocycles can be made to approximate naturally occurring molecules, that is, cyclic polyethers similar to macrocyclic antibiotics of the valinomycin and nonactin types and cyclic polyamines similar to porphyrins. Macrocycles are also useful as model compounds for the study of metal interactions with biological systems. The synthetic macrocycles thus represent an intriguing new area of coordination chemistry, the systematic study of which should lead to many interesting and useful chemical applications in the field of metal complexation in solution.

Ionic Concentrations and Activities in Soil Solutions

Abstract: The chemical composition of displaced soil solutions is used to illustrate the procedure for correcting measured ionic concentrations to actual ionic concentrations and ionic activities. The procedure distributes soil-solution electrolytes at equilibrium among their various ionic species by using equations for ion-activity coefficients, ion-pair dissociation, weak-acid and weak-base dissociation, and hydrolysis. More than a score of related equations had to be solved simultaneously; thus, mathematical solution was effected through the method of successive approximation. Rapid correction of soil-solution analytical data to actual concentrations and activities of individual soil-solution ions was made possible by using computer program.

Interlayer complexes in layer silicates. The structure of water in lamellar ionic solutions

Abstract: The stretching vibrations of water (H2O, HDO and D2O) in montmorillonite, hectorite, saponite and vermiculite are split into two components, similar to those seen in perchlorate solutions. Examination of lower hydrates and pyridine complexes of the layer silicates shows that the higher frequency component corresponds to hydrogen bonds to oxygens of Si—O—Si linkages, the lower frequency component to water-water bonds and hydrogen bonds to oxygens of Al—O—Si linkages. The observations are explained in terms of chains of hydrogen-bonded water molecules which form dielectric links between interlayer cations and oxygens on the silicate anion surface. This concept, together with information obtained on the distribution of charge on the surface oxygens, provides a qualitative explanation of the hydration properties of layer silicates, and is extended to account for the stability of organic complexes of montmorillonite and hectorite. Some analogies between interlayer complexes and ionic solutions are proposed.

Ionic Contamination and Transport of Mobile Ions in MOS Structures

Abstract: A fast, simple and very sensitive technique has been developed to determine the extent of ionic contamination of oxides in MOS capacitors. The method is capable of detecting better than 109 mobile ions/cm2 and is based on the measurement of the displacement current response to a slow linear ramp voltage at elevated temperatures. This yields an ionic displacement current peak whose area is proportional to the total mobile ionic space charge. The method is expected to be very useful for routine process and quality control applications. This technique has been used to study positive mobile charge behavior in silicon dioxide. The voltage dependence of the ionic displacement current indicates that trapping of ions occurs at the metal‐oxide interface and that ionic transport from the metal to the silicon interface is controlled by trap emission. Ion transport from the silicon to the metal interface is characterized by a single, bulk‐limited transport mechanism below 300°C with an activation energy that appears concentration dependent. Above 300°C an additional transport mechanism is observed which is slow in comparison to the primary transport mechanism.

Excess Electrons in Liquid Hydrocarbons

Abstract: Stable electronic charge carriers have been observed in n‐hexane, n‐pentane, benzene, and methylbutene with room temperature mobilities of 0.07, 0.07, 0.6, and 3.6 cm2 V−1·sec−1, respectively. The charge carriers were injected into the highly purified hydrocarbon liquids by photoemission of electrons from a low work function surface. Mobilities increase rapidly with temperature and obey an Arhennius expression with activation energies of 4.3 kcal mole−1 in hexane and 2.6 kcal mole−1 in methylbutene. The carriers in hexane could be drawn out of the liquid into the vapor and had a higher mobility in the solid than in the liquid at temperatures near the melting point. Current versus voltage measurements indicate that the injection process is controlled by transmission over the image barrier at the cathode. The mobilities of the injected charges in these fluids are more than 100 times ionic mobilities in the same fluids but considerably less than the mobilities of electrons in the rare‐gas liquids. The free e...

Infra-red studies of rutile surfaces. Part 1

Abstract: Samples of rutile prepared by hydrolysis of TiCl4 and by combustion of Ti(isoPrO)4 have been investigated by infra-red spectroscopic techniques to provide information on their surface hydroxylation and hydration. After outgassing at ambient temperatures the rutile surface carries both hydroxyl ions and adsorbed molecular water. The depopulation of the surface caused by raising the outgassing temperature follows a pattern that suggests there are two types of surface site for the adsorbed molecular species. Complementary studies of pyridine adsorption indicate that the molecular water is held on the surface as a coordinating ligand and also show the presence of two types of hydroxyl species on the ambiently outgassed oxide. Further studies of the adsorption of thionyl chloride, sulphur dioxide and hydrogen chloride vapours support the contention that the surface hydroxyls are ionic in character. In the case of HCl adsorption, evidence for two types of coordinately bonded water was found after exposure of the oxide to the dry acid gas. It was also found that the sample prepared from TiCl4, which carried chlorine in its surface layers, was more readily dehydroxylated than the “chlorine free” material prepared from the metal alkoxide. The chlorine containing sample also aggregated on storage whereas the pure material did not.

Matrix‐Isolation Study of the Interaction of Electrons and Alkali Metal Atoms with Various Nitrogen Oxides. Infrared Spectra of the Species NO−, NO2−, and N2O2−

Abstract: The infrared spectra which result when samples of NO2 are codeposited with the various alkali metals in an argon matrix at 4 or at 14°K are consistent with the occurrence of strong charge‐transfer interaction. In addition to isolated NO2−, previously identified in this system, ion pairs of general formula Mx+NO2− are stabilized. When NO is substituted for NO2, the infrared spectrum of the initial deposit shows an absorption between 1350 and 1375 cm−1 which can be assigned to the NO− stretching fundamental of Mx+NO− ion pairs, in good agreement with the vibrational spacing recently reported for ground‐state NO− in the gas phase. Weak charge‐transfer interaction occurs between alkali‐metal atoms and N2O in an argon matrix environment. Results of the present experiments can be explained by postulating that the upper, predominantly ionic state of the charge‐transfer complex decomposes producing O−, which may diffuse through the matrix. A new absorption which appears at 1205 cm−1 has tentatively been assigned ...

Cation Diffusion and Conductivity in Solid Electrolytes. II. Mathematical Analyses

Abstract: This paper constitutes Paper II of the series and presents theoretical analysis and supplements the results shown in Paper I. Equilibrium properties of the layer in which Na ions exist in β‐ and β″‐alumina are analyzed using the cluster variation method. Diffusion coefficients and ionic conductivities of Na ions in these two substances are derived using the path probability method.

On the nature of 4ƒ bonding in the lanthanide elements and their compounds

Abstract: A new model is proposed for the electronic configuration of the trivalent lanthanide metals in the condensed state. It is suggested that there are two kinds of 4ƒ electrons—the “atomic” 4ƒ electrons and the 4ƒ “band” electrons. The former are the 4ƒ electrons which are commonly associated with the trivalent metals and ions. The number of 4ƒ atomic electrons varies from zero for La to 14 for Lu and accounts for the normal magnetic susceptibilities observed in the elements and their compounds. The 4ƒ band electron, as the name implies, is one of the valence or conduction band electrons. The 4ƒ band electron occurs because the lowest of the empty energy levels, which vary from 14 for La to one for Tm, lies very close to the Fermi level (and thus is partially occupied by the conduction or valence band electrons) and not well above the Fermi level as has been commonly assumed previously or perhaps completely ignored. The 4ƒ band electron varies from about 0.7 of an electron for the light lanthanides to about 0.1 or less for the heavy lanthanides (for Lu there is no 4ƒ band electron since all 14 atomic 4ƒ levels are filled). The 4ƒ band electron does not contribute to the magnetic susceptibility, except as a conduction electron. It does, however, contribute to the bonding and thus influences the melting point and heat of sublimation. An analysis of these two physical properties permits one to estimate the fractional 4ƒ electron concentration in the valence band. The influence of the bonding 4ƒ electron on ionic and covalent compounds is also briefly discussed.

Approach to Alkali-Metal Chemisorption within the Anderson Model

Abstract: A theory of chemisorption relevant to alkali atoms on metal surfaces is presented. The virtual-impurity-state problem is modeled in the manner presented by Kj\"ollerstr\"om, Scalapino, and Schrieffer for solving the Anderson impurity problem in the low-density approximation (LDA). It is assumed that the binding or chemisorption energy of the alkali metal is composed of two parts, a metallic and an ionic component. Since considerable charge transfer from the alkali atom to the metal occurs, the LDA is appropriate for describing the metallic part of the binding. Another consequence of the large charge transfer is that the major portion of the binding results from an ionic type of bond between the partially charged alkali ion on the surface and a polarization or screening charge inside the metal. The results of the theoretical calculations indicate that binding energies for alkali atoms adsorbed on clean single-crystal faces of metals generally fall with in the range of 1.5-2.5 eV, in accord with available experimental data on metals such as W, Mo, Ta, and Ni.

Covalent-Ionic and Covalent-Metallic Transitions of Tetrahedrally Coordinated A N B 8 − N Crystals Under Pressure

Abstract: A microscopic analysis of the differences in Gibbs free energy between covalent, ionic, and metallic forms of ${A}^{N}{B}^{8\ensuremath{-}N}$ compounds is described. The analysis explains the success of the spectroscopic theory of chemical bonds in predicting the covalent-ionic transition at zero pressure as a function of $A$ and $B$. It also suggests that bond charge may play the role of a microscopic order parameter which determines the magnitude of the differences in energy between ionic and covalent structures at zero pressure and temperature.

Pressure sensitive adhesive containing carboxylic acid groups and polyvalent metal

Abstract: THE PRESSURE SENSITIVE ADHESIVE OF THE INVENTION HAS IMPROVED SHEAR RESISTANCE WHILE STILL HAVING GOOD TACKINESS, IT IS PREPARED BY EMULSION OR SOLUTION POLYMERIZATION, OR BY OTHER METHODS, AND HAS CARBOXYLIC ACID GROUPS THEREIN, AT LEAST SOME OF WHICH ARE BOUND OR CROSSLINKED BY A POLYVALEANT METAL, BY IONIC, POLAR, AND/OR COORDINATION BONDS. THERE ARE VARIOUS POSSIBLE THEORIES OR HYPOTHESES AS TO WHAT IS INVOLVED IN "CROSSLINKING," THE INVENTION TION NOT BEING LIMITED THERETO. THE INVENTION INCLUDES ADHESIVE TAPES AND OTHER ARTICLES AND THEIR MANUFACTURE, IN ADDITION TO THE ADHESIVE COMPOSITIONS.

On the Electronic Structure of Some Nitrogen‐Containing Molecules as Studied by Ab Initio SCF MO Calculations and High‐Energy Electron Spectroscopy

Abstract: Nitrogen 1s binding energies in HN3 and the potassium salts of NO2−, NO3−, and N3− are measured and interpreted in terms of ab initio SCF MO calculations. The valence orbitals must be represented by a double‐zeta basis of STO's to adequately interpret the chemical shifts. Inclusion of the lattice potential in the case of the ionic compounds allows a good correlation between calculated and experimental 1s binding energies to be obtained for both ionic and nonionic compounds.

Electron-Ion Interaction and the Fermi Surfaces of the Alkali Metals

Abstract: Fermi surface data of alkali metals interpreted in terms of interaction between conduction electrons and ionic lattice for deducing partial wave phase shifts

Theoretical and experimental investigations of the flocculation of charged particles in aqueous solutions by polyelectrolytes of opposite charge

Abstract: An electrostatic mechanism for the flocculation of charged particles by polyelectrolytes of opposite charge is proposed. The difference between this and previous electrostatic coagulation mechanisms is the formation of charged polyion patches on the oppositely charged surfaces. The size of a patch is primarily a function of polymer molecular weight and the total patch area is a function of the amount of polymer adsorbed. The theoretical predictions of the model agree with the experimental dependence of the polymer dose required for flocculation on polymer molecular weight and solution ionic strength. A theoretical analysis based on the Derjaguin-Landau, Verwey- Overbeek electrical double layer theory and statistical mechanical treatments of adsorbed polymer configurations indicates that flocculation of charged particles in aqueous solutions by polyelectrolytes of opposite charge does not occur by the commonly accepted polymerbridge mechanism. A series of 1, 2-dimethyl-5 -vinylpyridinium bromide polymers with a molecular weight range of 6x10^3 to 5x10^6 was synthesized and used to flocculate dilute polystyrene latex and silica suspensions in solutions of various ionic strengths. It was found that with high molecular weight polymers and/or high ionic strengths the polymer dose required for flocculation is independent of molecular weight. With low molecular weights and/or low ionic strengths, the flocculation dose decreases with increasing molecular weight.

Vibration-electronic coupling in the quenching of electronically excited alkali atoms by diatomics.

Abstract: This paper reviews the ionic intermediate curve crossing model and the quenching of electronically excited atoms by simple diatomics and extends previous calculations to include predictions for the partial cross sections of the first electronic state of all the alkali atoms by N2 and CO. Also included are calculations on the partial cross sections for Na quenching in high vibrational temperature environments, Na quenching by the inert gases, and the relaxation of N2 vibrational energy in collisions with alkali atoms. An extension of this curve crossing model to ionization processes in the alkali atoms and to reactions involving covalent curve crossing is briefly discussed.

Nuclear magnetic resonance and Raman studies of the aluminium complexes formed in aqueous solutions of aluminium salts containing phosphoric acid and fluoride ions

Abstract: 27 Al and 31P n.m.r. have been used to measure quantitatively the formation of complexes between aluminium ions and the ionic and molecular species present in phosphoric acid. The results are consistent with the presence of both monomeric and polymeric species in aqueous phosphoric acid. Five 31P lines were observed at low temperatures in solutions of an aluminium salt in aqueous phosphoric acid and these are interpreted as arising, respectively, from the complex Al,H3PO43+, from exchanging Al,H2PO42+ and Al(H2PO4)2+, from two binuclear aluminium species, and from a series of polymeric phosphoric acid ligands Al(H3PO4)n, n 2, although in this latter case the state of protonation of the ligand is not known. The protons in the system undergo fast exchange at all temperatures where the samples are liquid. Addition of fluoride ion to these solutions results in the formation of eight new fluoro-phosphato-aluminium complexes containing direct Al–F bonds, in addition to the known binary complexes AlFn(3–n)+. These complexes were revealed by 19F n.m.r. spectroscopy.

Thermodynamic properties of the molten thallium + tellurium system

Abstract: The thermodynamic properties of molten Tl + Te alloys have been determined by the e.m.f. method. The observed integral entropy of mixing becomes practically zero and enthalpy shows a minimum at the stoichiometric composition Tl2Te. The excess stability also exhibits a strong tendency to compound formation at this composition. It is concluded from these observations, together with those of the electrical properties,1–5 that the molten Tl + Te system can be treated as two pseudo-binary systems, Tl + Tl2Te and Tl2Te + Te, and that around the stoichiometric composition Tl2Te a high local ordering can be considered because of the ionic character of the chemical bonding.

Ionic Raman Effect. II. The First-Order Ionic Raman Effect

Abstract: A theory previously developed for the Raman scattering of infrared light by the modulation of the ionic contribution to the polarizability of a crystal by the displacements of the atoms from their equilibrium positions has been applied to the calculation of the scattering efficiency of a pure crystal having a first-order electric dipole moment and cubic anharmonicity in the potential energy. The requirements on crystal symmetry for a nonvanishing scattering efficiency are developed, and it is shown that only noncentrosymmetric crystals can exhibit the effect. The symmetries of the ionic Raman tensor are presented for the 21 crystal classes lacking a center of inversion. A numerical estimate of the scattering efficiency is given for the case of gallium arsenide.