Electronegative Elements Research Articles

Systematics of secondary-ion-mass spectrometry relative sensitivity factors versus electron affinity and ionization potential for a variety of matrices determined from implanted standards of more than 70 elements

We have measured and plotted the dependence of secondary-ion-mass spectrometry (SIMS) relative sensitivity factor (RSF) on electron affinity and ionization potential of up to 74 elements implanted into 23 materials, measured using oxygen-ion bombardment and positive SIMS, and cesium-ion bombardment and negative SIMS. Reproducibility of ±60% in RSF has been demonstrated for many of these implanted standards over a period of 8 years in several Cameca magnetic sector instruments, especially in Si, GaAs, and HgCdTe matrices. More recently, reproducibilities of ±20%–30% have been achieved using more controlled experimental techniques. Similarities among plots of logRSF versus ionization potential or electron affinity have been found for a variety of semiconductor, metal, and insulator matrices. Universal patterns and trends are observed for oxygen bombardment and positive SIMS, and for cesium bombardment and negative SIMS. Four major regions are seen in the dependence of logRSF on ionization potential, one with possibly three branches with slightly differing slopes, that are characterized by elements from various groups of the periodic table. There are two major regions in the plots of RSF versus electron affinity, one of which is a region of constant RSF versus electron affinity, which includes the more electronegative elements, and meaning that the RSF is a constant for most of the elements commonly analyzed using negative (cesium) SIMS. This constant RSF has been measured for 20 matrices. We report the values of slope of logRSF versus ionization potential for the matrices studied and discuss the possible extension to other matrices. We tabulate the values of RSF for 74 elements in Si and for 69 elements in GaAs, as examples. Tentative explanations of the features of these dependencies are consistent with existing theories and models. We give generalized patterns of RSF (ion yield) versus ionization potential or electron affinity and an equation from which RSFs can be calculated for the matrices studied, and possibly others.

Systematics of positive secondary ion mass spectrometry relative sensitivity factors for Si and SiO2 measured using oxygen and argon ion bombardment

We have measured normalized positive ion yields of more than 20 elements implanted into SiO2 and compare them with positive ion yields of the same elements sputtered from Si by oxygen and argon ion bombardment. All measurements were made using similar instruments and similar primary ion beam conditions; thus, we compare secondary ion emission from an unoxygenated matrix (Si using argon ion bombardment), from a partially oxygenated matrix (Si using oxygen ion bombardment), and from a fully oxygenated matrix (SiO2). Plots of the logarithm of secondary ion yield or secondary ion mass spectrometry relative sensitivity factor (RSF) versus ionization potential of the sputtered impurity elements exhibit primary linear trends for these three conditions, the slopes of which decrease with increasing oxygenation. A trend line of opposite slope for impurity elements that have ionization potential greater than about 10.5 eV is observed in each case. This latter trend moves to lower values of yield (higher RSF) with increasing oxygenation, perhaps as the result of competition from electronegative elements with oxygen in forming element–Si bonds. These observed changes are primarily the result of increasing the oxygen content in the surface of the Si.

Number of surface V = O species of promoted (VO) 2P 2O 7 catalysts

The number of surface V Ł O species on promoted (VO) 2P 2O 7 catalysts was determined by means of the nitric oxide-ammonia rectangular pulse technique. The number of surface V  O species increased with the addition of a less electronegative element, while it decreased with the addition of an electronegative one.

Theoretical study of cimetidine and rigid analogues

An electronic and conformational study using semiempirical MNDO calculations on cimetidine and rigid analogues was carried out. Imidazolylthiophene and imidazolylfuran rigid analogues of cimetidine were proposed and theoretical calculations were carried out on these molecules. For the molecules under study, all the possible configurational isomers with respect to the cyanoguanidine group were taken into account. Cimetidine showed a high molecular flexibility, the folded and half-folded conformations being the preferred ones. Folded and half-folded conformations of cimetidine were assumed to present the biologically advantageous spatial ordering. Imidazolylphenylene derivatives showed a different electronic behavior from that of cimetidine. This difference may be the reason for the lower biological activity of the phenylene analogues. In contrast, the imidazolylthiophene and imidazolylfuran analogues showed molecular electrostatic potential maps closely similar to those of cimetidine. The presence of an electronegative structural element (S or O) between the two electron systems (imidazole ring and cyanoguanidine group) appears to yield critical electronic effects, which may be related to the antagonist activity on H 2-histamine receptors.

Bromine Function in Halite Geochemistry

Of the halogens or salt formers, bromine is the only nonmetal which occurs naturally as a poisonous liquid much denser than water. The power of its atoms, expressed by a valence of 1 and 5, makes it unite directly with a large number of metallic elements to form salts. As a rare and strongly electronegative element of group VII in the periodic table, bromine exists in seawater and evaporitic brines as bromide with a ratio to chlorinity of 0.00348. Most water detains only about 1 ppm bromide for each 300 ppm of chloride. The most abundant source of bromine is ocean water (65 ppm Br), but richer peps occur in salt deposits and primarily in mineral brines. Atomic absorption spectrophotometric resolutions of Permian Castile halites exposed low values of bromine compared with its higher quantities in modern oceans like the Mediterranean. Bromine analyses of the two petrographically distinct forms of halite that characterize many ancient evaporite deposits, as in the Elk Point basin fields of Alberta, imply they crystallized from brines of noticeably different concentrations. Bromine in halite has been used as a paleosalinity indicator and a stratigraphic marker. Bromine liquid, with an atomic weight of 79.904 and atomic numbermore » 35, is used in producing gasoline antiknock mixtures, fumigants, photographic chemicals, drilling fluids, and fire retardants. It is also highly toxic and corrosive as bromine gas. Bromine contents greater than 1 ppm may be unsafe in the atmosphere, and a dose of 500 ppm can lead to death in less than an hour.« less

A cautionary note on the use of the frozen‐core approximation for correlation energy calculations involving alkali metals

AbstractTest calculations have shown that correlation energies calculated using the frozen‐core approximation in programs, such as the Gaussian series, that assume the lowest MOs to be the core orbitals may be significantly in error. Some valence orbitals in systems involving the heavier alkali metals and electronegative elements have lower energies than the highest core orbitals of the metal and are therefore erroneously omitted from the correlation energy calculation. Some examples are discussed.

The effect of the halide on the Lewis acidity of organotin halides

Thermodynamic parameters for adduct formation by R n SnX 4− n , where R is methyl, ethyl, or butyl, and X is Cl, Br, or I, with tributylphosphine (TBP) in benzene and chlorobenzene solvents are reported. These data are combined with previously reported data for the same systems with triphenylphosphine oxide (TPPO). The enthalpies of adduct formation generally increase in the order Cl < Br < I thus producing a reversal of the acid-strengthening effects due to substitution of more electronegative elements. Equilibrium constants, however, increase in the order I < Br < Cl, indicating a dominance of the entropy term for formation of these organotin halide adducts with TBP and TPPO.

Acute Fluoride Toxicity

Acute intoxication with inorganic fluoride disrupts numerous physiological systems. As a potent acid it acts corrosively on the skin and mucous membranes, producing severe burns. As the most electronegative element it tightly binds many cations essential to homeostasis, producing, for example, profound hypocalcaemia and resultant inhibition of normal blood coagulation. As a metabolic poison it stimulates some enzymes, such as adenylate cyclase, and severely inhibits others, such as Na(+)-K(+)-ATPase and the enzymes of carbohydrate metabolism. Death can result from these processes and also from a delayed, explosive hyperkalaemia. Therapy of acute poisoning is aimed first, at preventing the absorption of fluoride by incorporating it into insoluble fluoride compounds; secondly, at enhancing fluoride tolerance by maintaining normal blood pH and electrolytes, and aggressive general support of the toxic patient; and thirdly, at manipulating renal excretion or removing fluoride with dialysis and haemoperfusion. If the poisoned patient can be supported for 24 hours, the prognosis improves markedly, although delayed toxicity can occur.

Structural Determinants of Phenoxazine Type Compounds Required to Modulate the Accumulation of Vinblastine and Vincristine in Multidrug-Resistant Cell Lines

Phenoxazine and seven other structurally related compounds were investigated to determine whether they would increase accumulation of Vinca alkaloids in multidrug-resistant (MDR) GC3/C1 (human colon adenocarcinoma) and KB-ChR-8-5 (HeLa variant) cell lines. Among eight compounds examined, phenoxazine caused greater accumulations of vincristine (VCR) and vinblastine (VLB) than the other chemosensitizers. The structure-activity relationship of these compounds for anti-MDR activity suggested an ideal tricyclic ring structure with a basic nitrogen atom at position 10 for modulating the accumulation of Vinca alkaloids. Addition of oxygen to position 5 of the tricyclic ring system further increased the activity, implying that a highly electronegative element with one, or more, lone pair of electrons in the nucleus opposite to heterocyclic nitrogen was a requirement for better anti-MDR activity. The relationship between the concentration of phenoxazine and the potentiation of Vinca alkaloid accumulation in comparison to verapamil was examined. For VCR in GC3/C1 cells, maximal modulation indices were: for verapamil, 1.8; phenoxazine, 8.6; and for VLB, 1.3 for verapamil compared to 3.3 for phenoxazine. In KB-ChR-8-5 cells, for VCR the maximal modulating index values were 9.0 and 4.3, respectively, and for phenoxazine and verapamil and for VLB were 5.0 and 3.7, respectively. Accumulations of VLB in GC3/C1 cells were similar in the presence of 1 microM phenoxazine or 10 mM sodium azide plus 10 mM 2-deoxyglucose. The effects of verapamil and phenoxazine on the accumulation of Vinca alkaloid were additive. Further, phenoxazine decreased the efflux of VLB by 30% in KB-ChR-8-5 cell line and 10% in GC3/C1 cells. In addition to enhancing the cytotoxicities of VCR and VLB, phenoxazine competed relatively weakly for binding to P-glycoprotein with [3H]azidopine and moderately with [3H]azidoverapamil, at equal concentrations, suggesting that the multidrug transporter may be the primary target for phenoxazine.

Electron counting model and its application to island structures on molecular-beam epitaxy grown GaAs(001) and ZnSe(001).

The principal reconstructions found on the low-index planes of GaAs and ZnSe can be explained in terms of a simple electron counting model. A surface structure satisfies this model if it is possible to have all the dangling bonds on the electropositive element (Ga or Zn) empty and the dangling bonds on the electronegative element (As or Se) full, given the number of available electrons. This condition will necessarily result in there being no net surface charge. The justification for this model is discussed. The GaAs(001)-(2\ifmmode\times\else\texttimes\fi{}4) reconstruction is known to involve surface dimers. It is shown that a (2\ifmmode\times\else\texttimes\fi{}4) unit cell with three dimers and one dimer vacancy is the smallest unit cell that satisfies the electron counting model for this surface. The electron counting model is used to explain the structure of islands imaged by scanning tunneling microscopy on the GaAs(001)-(2\ifmmode\times\else\texttimes\fi{}4) surface. The model shows that island structures built up from complete (2\ifmmode\times\else\texttimes\fi{}4) unit cells can be stable if they extend in the 2\ifmmode\times\else\texttimes\fi{} direction, but not if they extend in the 4\ifmmode\times\else\texttimes\fi{} direction. These island structures can also provide an explanation for the different step structures seen on GaAs(001) vicinal surfaces. Much less is known experimentally about step and island structures on ZnSe(001). Structures on this surface predicted by the electron counting model differ significantly from those found on GaAs(001).

The effect of catalyst preparation on the performance of alumina-supported ruthenium catalysts: II. The impact of residual chloride

The impact of residual chloride on the properties and performance of a series of Ru Al 2O 3 catalysts has been studied. This work departs from previous studies in that it examines the poisoning and promoting effects of this electronegative element in CO hydrogenation as a function of the dispersion of the catalyst. The dispersion and structure of the particles are regulated by the choice of the precursor used during preparation and by the impregnation conditions. We find that, in general, chloride residues poison catalysts with a high dispersion but provide a promotional effect for catalysts with a poor dispersion.

Derivation of gold by oxidative metamorphism of a deep ductile shear zone: Part 2. Evidence from the Bamble Belt, south Norway

Abstract The Bamble Belt of south Norway is a major transcurrent shear zone, 30 km wide, comprised of lower Proterozoic supracrustal rocks and tholeiitic intrusions. At 1.54 Ga the belt was metamorphosed at ∼800°C and a depth of ∼25 km to granulite and upper amphibolite grade. This was coincident with large-scale displacement by ductile deformation, which permitted the pervasive passage of fluids through the belt during metamorphism. Previous work has shown that fluid inclusions in the granulites are predominantly CO 2 , which led to a proposal that the granulites were derived from amphibolite facies rocks by dehydration in a stream of CO 2 -rich fluid of possible mantle origin. In the course of this, rubidium was removed from the granulites. The present study has shown that metamorphic fluids caused pervasive oxidation of the rocks. Mafic rocks re-equilibrated at an oxygen fugacity 2.7 log units above their likely pre-metamorphic condition. Sulphide minerals, including pyrite, pyrrhotite, and chalcopyrite, were dissolved. This created a relatively oxidized, sulphur-rich fluid, in which SO 2 and H 2 S were in approximately equal amount. A fluid of this composition is a potent solvent for the more electronegative transition elements, such as Au + , Sb 3+ and As 3+ . These elements have been strongly depleted throughout the belt. Gold in the mafic rocks averages 0.17 ppb, which is 4% of its crustal abundance in this rock type. Average contents for other rock units vary from 0.15 to 0.37 ppb Au, or more than an order of magnitude less then their likely original composition. These data are consistent with a model where oxidized, CO 2 -rich fluids passing through a ductile shear zone dissolved gold and transferred it upwards within the permeable shear. Loss of this amount of gold from the volume of lower crust contained within the 30 km-wide shear zone would have provided a large supply of this metal for concentration at shallower levels in the crust, where the ductile shear narrowed to a brittle fault. The oxygen fugacity of the metamorphic fluids in the Bamble Belt was such that, on cooling, the fluids may have precipitated sulphate minerals, hematite and pyrite depleted in 34 S: all features found in some major Archean quartz-carbonate gold deposits, such as Kalgoorlie.

Nuclear quadrupole interaction in solid HF and trifluoroaminoboranes

Using the time differential perturbed angular distribution method (TDPAD) solid HF and trifluoroaminoboranes have been investigated. In the case of solid HF some new aspects appear in the interpretation of former experiments. The new measurements either reproduce the older data that yielded one frequency and a distinct ν, or show two frequencies and no distinct ν. This discrepancy can be explained with different target preparations. While the one-frequency experiments were done with untempered targets the two-frequency targets were tempered. Trifluoroaminoboranes (F 3BNH 3) are known as charge-transfer complexes. Since ammonia acts preferentially as an electron donor and 19F is the most electronegative element, a lowering of the observed coupling constant should appear. Experiment, however, does not support this; it gives an unchanged coupling constant, but the asymmetry parameter is changed by a factor of more than 2. This behaviour can be understood by calculating the electron distribution in both molecules within the framework of the Townes and Dailey theory. It turns out that charge transfer does take place, but the transferred charge does not lead to a more isotopicc electronic environment for fluorine, but rather reduces the asymmetric population of its p x̂ and p ŷ orbitals.

ChemInform Abstract: Pentamethylcyclopentadienyl Compounds of Electronegative Elements

ChemInformVolume 19, Issue 37 Isocyclic Compounds ChemInform Abstract: Pentamethylcyclopentadienyl Compounds of Electronegative Elements F. X. KOHL, F. X. KOHL Univ. Bielefeld, D-4800 BielefeldSearch for more papers by this authorK.-H. SCHWARTZEN, K.-H. SCHWARTZEN Univ. Bielefeld, D-4800 BielefeldSearch for more papers by this authorP. JUTZI, P. JUTZI Univ. Bielefeld, D-4800 BielefeldSearch for more papers by this author F. X. KOHL, F. X. KOHL Univ. Bielefeld, D-4800 BielefeldSearch for more papers by this authorK.-H. SCHWARTZEN, K.-H. SCHWARTZEN Univ. Bielefeld, D-4800 BielefeldSearch for more papers by this authorP. JUTZI, P. JUTZI Univ. Bielefeld, D-4800 BielefeldSearch for more papers by this author First published: September 13, 1988 https://doi.org/10.1002/chin.198837147Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume19, Issue37September 13, 1988 RelatedInformation

ChemInform Abstract: New and Unexpected Reactivity of Saturated Fluorocarbons.

The carbon-fluorine bond, noted for its strength1, has been of chemical interest2 even before Moissan's discovery of elemental fluorine. The most electronegative element, fluorine is uniquely capable of replacing all the hydrogen atoms in every hydrocarbon system3, yielding materials such as polytetrafluoroethylene renowned for their combination of rare physical properties, out-standing chemical inertness and high thermal stability4, with sig-nificant modern technological applications5,6. Reaction of satur-ated fluorocarbons requires extreme conditions1, for example treat-ment with metals at ∼500 °C7 or high-energy irradiation8. Following an observation by MacNicol and McGregor (unpublished data) of an unprecedented reactivity under mild conditions we now report specifically the efficient transformation of perfluorodecalin (1) to known host molecules by arenethiolate nucleophiles in dipolar aprotic solvent. This chemistry is not only of fundamental mechanistic interest, but also creates new synthetic possibilities in various fields. For example, preparing novel hosts for inclusion chemistry9, a subject attracting much current attention.

New and unexpected reactivity of saturated fluorocarbons

The carbon-fluorine bond, noted for its strength1, has been of chemical interest2 even before Moissan's discovery of elemental fluorine. The most electronegative element, fluorine is uniquely capable of replacing all the hydrogen atoms in every hydrocarbon system3, yielding materials such as polytetrafluoroethylene renowned for their combination of rare physical properties, out-standing chemical inertness and high thermal stability4, with sig-nificant modern technological applications5,6. Reaction of satur-ated fluorocarbons requires extreme conditions1, for example treat-ment with metals at ∼500 °C7 or high-energy irradiation8. Following an observation by MacNicol and McGregor (unpublished data) of an unprecedented reactivity under mild conditions we now report specifically the efficient transformation of perfluorodecalin (1) to known host molecules by arenethiolate nucleophiles in dipolar aprotic solvent. This chemistry is not only of fundamental mechanistic interest, but also creates new synthetic possibilities in various fields. For example, preparing novel hosts for inclusion chemistry9, a subject attracting much current attention.

Atomic radii in ternary adamantines

Bonded radii are derived for eight electropositive and four electronegative elements from line plots of total valence electron densities [Jaffe and Zunger, Phys. Rev. B28, 5822 (1983); B30, 741 (1984)] for 10 ternary chalcopyrites, in order to aid in understanding the defect chemistry of such compounds. They scale well with tetrahedral sulphide crystal radii, when a spherical atom approximation is made, in which case they are significantly closer to these than to covalent tetrahedral radii, as illustrated for several ternary chalcogenides. Their derivation confirms that the electronegative elements in these tetrahedrally bonded ternaries are better described by tetrahedrally distorted spheres. Still, models using these radii are to be preferred over the usual ball-and-stick types. This is illustrated by a few examples concerning native defects and ion mobility in some ternaries.

Valence‐bond calculations on N2 and isoelectronic species

AbstractValence‐bond calculations are reported for the isoelectronic series of molecules and ions: N2, CO, BF, NO+ and CN−. The most important structures are NN, CO, BπF, N+O and CN. Hybridization of the 2s and 2p orbitals is important. Only two or three structures are required to obtain an energy lower than that obtained with the molecular orbital approximation. Structures in which the electronegative element loses a σ‐orbital or gains a π‐orbital are favored. π‐bonds tend to be favored over σ‐bonds. The bond in NO+ resembles that in CO, whereas that in CN− resembles the bonding in N2.

ChemInform Abstract: Elemental Fluorine Generated Chemically.

An inorganic chemist working for a rocket manufacturing company has proved the textbooks wrong by generating significant amounts of elemental fluorine by purely chemical means for the first time. Remarkably, his simple, straightforward method involves reagents that have been known for at least 80 years. Chemists, including many notable ones, have tried to produce elemental fluorine chemically for at least 173 years, says Karl O. Christe of Rockwell International Corp.'s Rocketdyne Division in Canoga Park, Calif. All such attempts have failed. This sobering fact, he says, together with fluorine's well-established reputation as the most electronegative and most reactive element, has ingrained into chemists the notion that purely chemical—as opposed to electrochemical—reactions cannot liberate fluorine from its compounds. Christe set out to show that this wasn't necessarily so. He reasoned that a Lewis acid such as antimony pentafluoride (SbF 5 ) would react with a salt of the stable hexafluoromanganate(IV) ...

NMR and structural features of noble-metal fluorides

This evidence enables one to relate the distinctive chemical shifts for fluorine, oxygen, and other electronegative elements in noble-metal compounds to the major partici pation of 4d and 5d electrons in the bonds. These bonds of σ and τ tupes are indicated as of partially covalent character, and in some cases there is a definite hybrid character in the orbitals. Further refinement of the description in this model may be based on incorporating the nonorthogonality of the metal and ligand orbitals.