Group Of Periodic Table Research Articles

Electrical transport properties of some liquid metals

In the present article, we report the electrical transport properties, namely, the electrical resistivity ( ρ), the thermoelectric power (TEP) ( α), and the thermal conductivity (σ) of several monovalent, divalent and polyvalent liquid metals of the different groups of the periodic table on the basis of model potential formalism. The well known empty core model (EMC) potential of Ashcroft is used for the first time with seven local field correction functions proposed by Hartree (H), Hubbard-Sham (HS), Vashishta-Singwi (VS), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) in the present computation and found suitable for such study. In the calculation of these properties, we have used the values of the theoretical structure factors due to hard core fluid theory. It is concluded that the comparisons of present and theoretical or experimental findings, wherever they exist, are highly encouraging.

ToF-SIMS investigation of the cationization of several lubricant components

Cationization of molecular substances results often in the emission of characteristic peak patterns of secondary ions (SI) of these molecular species and is accompanied by matrix-enhanced SI yields. Besides the cationization of molecular overlayers on substrates of periodic table group IB elements, recent especially matrix-enhanced SIMS by physical vapor deposition (PVD) processes of Ag and Au was in the focus of investigations. In this work, selected lubricants components were investigated by ToF-SIMS, using different methods for cationization: (i) substrate cationization with periodic table group IA and IB elements (Cu, Ag, Cs, Au), (ii) cationization by dissolved salts of group IA and IB elements (Li, K, Na, Cu, Ag), and (iii) the in situ PVD by sputtering of group IB element targets (Cu, Ag, Au) by using the pulsed dual source column (DSC) of a ToF-SIMS instrument and thick lubricant layers on silicon wafers positioned in the immediate vicinity of the sputter crater. The Cu- and Ag-cationization of the investigated trimethylol-propane esters TMP(C8/C10) and poly-alpha-olefins (PAO) were possible with all specified methods, whereas only the esters were cationized also by alkaline elements (Li, Na, K, Cs). Au-cationization products were only observed for volatile PAO components that have deposited on the fresh cleaned surface of the sputter crater bottom of the Au-target.

Study on the contamination of heavy metals and their correlations in mollusks collected from coastal sites along the Chinese Bohai Sea

Mollusks living in seas can accumulate heavy metals, and may serve as excellent passive biomonitors. During a period of 1 year, bioaccumulation of As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, and Zn was examined in nine kinds of mollusks ( Rapana venosa, Neverita didyma, Scapharca subcrenata, Mytilus edulis, Amusium, Crassostrea talienwhanensis, Meretix meretrix, Ruditapes philippinarum, and Mactra veneriformis), which were collected at eight coastal sites along the Chinese Bohai Sea. Metal concentrations were directly determined by inductively coupled plasma mass spectrometer (ICP-MS). Two certified reference materials, dogfish muscle (DORM-2) and mussel (GBW 08571), were used to validate the methods, and the recoveries were within 83.72–112.30% of the certified values. Bioaccumulation of metals varied strongly among sampling sites and species. Statistical analysis (one-way ANOVA) indicated that different species examined showed different bioaccumulation of metals, and perhaps they could be used as potential biomonitors to investigate the contamination levels of heavy metals. Principal component analysis (PCA) and correlation analysis were used to study the relationships between these heavy metals. The results showed that, in nine mollusks' tissues, there are significant correlations between these elements in adjacent main group or subgroup in periodic table of elements.

RF plasma deposition of thin Si xGe yC z:H films using a combination of organometallic source materials

Elements of the IV group of periodic table have been strongly present in the fast development of PECVD techniques for the last two decades at least. As a result, deposition technologies of such materials as a-Si:H, a-C:H, mμ-C:H or DLC have been successfully established. What has followed is an ever growing interest in binary systems of the A x (IV)B y (IV):H kind. One possible way to deposit such systems is to use organosilicon compounds (to deposit Si x C y :H films) or organogermanium compounds (to deposit Ge x C y :H films), as source substances. The present paper reports on a RF plasma deposition of a Si x Ge y C z :H ternary system, using a combination of organosilicon and organogermanium compounds. Thin Si/Ge/C films have been fabricated in a small volume (ca. 2 dm 3) parallel plate RF plasma reactor using, as a source material, a combination of tetramethylsilane (TMS) and tetramethylgermanium (TMG) vapours carried by argon. SEM investigations reveal a continuous compact character of the coatings and their uniform thickness. The elemental composition of the films has been studied using EDX analysis. The results of the analysis show that the elemental composition of the films can be controlled by both the TMG/TMS ratio of the initial mixture and the RF power input. Ellipsometric measurements show good homogeneity of these materials. Chemical bonding in the films has been studied using the FTIR technique. Bandgap calculations have been carried out using ellipsometric data and by applying both the Tauc law and the Moss approach.

Microbial methylation of metalloids: arsenic, antimony, and bismuth.

A significant 19th century public health problem was that the inhabitants of many houses containing wallpaper decorated with green arsenical pigments experienced illness and death. The problem was caused by certain fungi that grew in the presence of inorganic arsenic to form a toxic, garlic-odored gas. The garlic odor was actually put to use in a very delicate microbiological test for arsenic. In 1933, the gas was shown to be trimethylarsine. It was not until 1971 that arsenic methylation by bacteria was demonstrated. Further research in biomethylation has been facilitated by the development of delicate techniques for the determination of arsenic species. As described in this review, many microorganisms (bacteria, fungi, and yeasts) and animals are now known to biomethylate arsenic, forming both volatile (e.g., methylarsines) and nonvolatile (e.g., methylarsonic acid and dimethylarsinic acid) compounds. The enzymatic mechanisms for this biomethylation are discussed. The microbial conversion of sodium arsenate to trimethylarsine proceeds by alternate reduction and methylation steps, with S-adenosylmethionine as the usual methyl donor. Thiols have important roles in the reductions. In anaerobic bacteria, methylcobalamin may be the donor. The other metalloid elements of the periodic table group 15, antimony and bismuth, also undergo biomethylation to some extent. Trimethylstibine formation by microorganisms is now well established, but this process apparently does not occur in animals. Formation of trimethylbismuth by microorganisms has been reported in a few cases. Microbial methylation plays important roles in the biogeochemical cycling of these metalloid elements and possibly in their detoxification. The wheel has come full circle, and public health considerations are again important.

Regularities of Vaporization of Periodic Table Group IVA Element Phosphates

The vaporization of glass-forming phosphates of the periodic table Group IVA elements is studied by high-temperature mass spectrometry. Analyses of qualitative and quantitative vapor compositions have revealed a number of regularities that allow the prediction of the character of the vaporization of polyvalent element phosphates.

Silicon anisotropic etching in alkaline solutions IV: The effect of organic and inorganic agents on silicon anisotropic etching process

Silicon anisotropic etching process in organic and inorganic solutions has been studied. Experimental results on silicon etching in KOH and TMAH solutions with and without IPA addition have been presented. Etching rate curves versus solution concentration were plotted for different crystallographic planes with special emphasis on high-indexed ones. A comparison of our own experimental results with the results of other authors, concerning silicon anisotropic etching process in hydroxides of other metals from the first group of periodic table, revealed that their ions and molecules contained in the solution play an important role in the process and influence its anisotropy. The observations led us to some general conclusions regarding physical and chemical phenomena associated with the silicon anisotropic etching. We have suggested that the lowering of etching rates is connected with adsorption of cations and organic additions on some crystallographic planes.

Comparison of density of states of transition metal disilicides and their related compounds systematically calculated by a first-principle pseudopotential method using plane-wave basis

Density of states of transition metal disilicides and their related compounds of the following types of structures have been calculated by a first-principle pseudopotential method using plane-wave basis, CASTEP; CaF 2, α- and β-FeSi 2, TiSi 2, ZrSi 2, CrSi 2, MoSi 2, Mn 4Si 7, Ru 2Si 3, and AlB 2. The principle of “DOS at Fermi level would be hopefully smaller in energetically-favored structure” is valid in most of silicides except for IIIa elements. The broadening of the energy difference between the bonding and anti-bonding states by promotion to the heavier element in the same group in periodic table is dependent on the crystal structure and this may cause the transition of the structure in the same group. Semiconducting property of ReSi 2 is probably due to the vacancies located at silicon sites because DOS at Fermi level has relatively large value for stoichiometric ReSi 2. Also, it is pointed out that the formula of Mn 11Si 19 is not consistent with the intrinsic semiconducting nature.

Metal−Oxygen Cluster Compounds (Heteropoly Oxometalates) of 1B and 3B Monovalent Cations and Their Micropore Structure

Silver and thallium, representatives from the periodic table's groups 1B and 3B, respectively, were employed as cations to synthesize stoichiometric and nonstoichiometric salts of 12-tungstophosphoric, 12-molybdophosphoric, and 12-tungstosilicic acids. All the solids, except silver 12-molybdophosphate, have high surface areas and microporous structures, as shown from the analysis of nitrogen adsorption−desorption isotherms obtained at 77 °K. Powder X-ray diffraction, temperature-programmed desorption, infrared spectroscopy, and 1H MAS NMR spectroscopy are employed to characterize the synthesized materials.

Spectroscopic Properties of Polycyclic Aromatic Compounds. Part III: Fluorescence Emission and Quenching Behavior of Periodic Table Group 16 Hetero-Atom Derivatives

Fluorescence emission spectra are reported for benzo[b]naphtho[2,3d]furan, dinaphtho[l,2b:l′,2′d]furan, dinaphtho[2,lb:l′,2′d]furan, dibenzo[2,3:10,11]perylo[l,12bcd]furan, dibenzo[2,3:10,ll]perylo-(l,12bcd]thiophene, naphtho[l,8bc:5,4b′c′]dipyran (also called 1,6-dioxapyrene), and naphtha[l,8bc:4,5b′c′]dipyran (also called 1,8-dioxapyrene) in organic nonelectrolyte solvents of varying polarity. Results of these measurements indicate that dinaphtho[l,2b:l′,2′d]furan exhibits slight signs of probe character as evidenced by changing emission intensity ratios; however, the dynamic range was much too small to classify this molecule as a polycyclic aromatic compound probe. The effect of nitromethane and 1,2,4-trimethoxybenzene as selective quenching agents was also examined. Nitromethane was found to quench fluorescence emission of all the aforementioned compounds except benzo[b]naphtho[2,3d]furan.

Cross-reactivity to palladium and nickel studied in the guinea pig.

In recent years there have been several reports on concomitant patch test reactions to palladium and nickel, which belong to the same group in the periodic table. Exposure to palladium mainly takes place via dental alloys and jewelry. However, the clinical relevance of simultaneous reactivity to these metals is unknown. To elucidate the question of cross-reactivity, guinea pigs were induced with palladium or nickel and simultaneously challenged with palladium and nickel. Animals sensitized to palladium according to the guinea pig maximization test method (GPMT) or to a new method by van Hoogstraten & Scheper (H&S) reacted to palladium as well as to nickel. On the other hand, animals sensitized to nickel according to H&S reacted to nickel but not to palladium. The GPMT shows that palladium is a more potent sensitizer than nickel: could palladium be the primary sensitizer in humans?

ChemInform Abstract: Astatine: Its Organonuclear Chemistry and Biomedical Applications

Publisher Summary Astatine, the fifth and heaviest member of the Periodic Table Group VIIB (the halogens), is the earth's rarest naturally occurring element. Many aspects of the nuclear physics, and inorganic and organic chemistry, of the astatine radionuclides have been the subject of a number of excellent reviews. The possibility of their existence was predicted from the β-decay of polonium. The relationship between the emitted α-particle energy and mass number of the astatine isotope is presented. Preparation of the isotopes of astatine is more difficult than with most radionuclides, as they cannot be synthesized by neutron irradiation; this precludes the use of a nuclear reactor. Numerous nuclear reactions have been employed to produce astatine. Three of these are particularly suited for routine preparation of the relatively long-lived isotopes with mass numbers 209, 210, and 211. Astatine can be readily and routinely obtained in an inorganic form suitable for chemical and biomedical application from the α-irradiated bismuth target by either extractive or dry distillation techniques. Distillation of astatine from molten metallic bismuth is the most widely used technique for separation of the radionuclide. Astatine, regardless of its electronic state (vide infra), appears to possess many physiobiochemical properties similar to those of its nearest homolog iodine.

A Comparison of Amino Acids Separation On Zn, Cd, and Hg Impregnated Silica Layers

Abstract TLC separation of amino acids on silica gel impregnated with different concentrations (0.1, 0.2 & 0.5%) of Zn, Cd and Hg ions, belonging to same group in periodic table, in a new solvent system BuAc-MeOH-HoAc-Pyr (20:20:5:5) is compared

Ionic conductivity of nitrides

Electrical conductivity of nonmetallic aluminium, magnesium, calcium and lanthanum nitrides has been measured in nitrogen, ammonium and argon over the temperature range 973–1673 K. The nature of the conductivity has been investigated using the emf method in a cell with separate gas compartments, using controlled nitrogen partial pressure. It has been shown, that the investigated nitrides of the II and III groups of the Mendelleev's periodic table are mixed conductors, the ionic conductivity part of which varies on temperature and nitrogen partial pressure.

The catalytic effects of uranium oxides and salts in carbon oxidation

The gasification reactions of carbon belong to an unusual class of heterogeneous processes involving the conversion of a solid phase into gaseous products. These reactions, which are of great technological importance, are catalyzed by many diverse types of inorganic species. In fact, active catalysts for carbon oxidation include members of every group in the Periodic Table. Although the detailed mechanism of few of these catalytic reactions have been unequivocally determined, it is generally agreed that cyclic redox processes on the carbon surface are probably the basis for the catalytic behavior. The metal uranium, which forms a complex series of interconvertible oxides, has apparently not hitherto been investigated as a catalyst for carbon oxidation and hence would provide a useful test for the redox mechanism. Uranium is found as a minor element in many coals, so that an understanding of its catalytic behavior during coal combustion would be of technological interest. This note describes the results of a study of the behavior of series of uranium oxides and uranyl salts as catalysts for the oxidation of graphite in the temperature range 500-1000/sup 0/C. 15 references.

Advances in polymerization catalysts based on 4 and 5F groups of periodic table

So far, in the development of new catalyst systems, the attention of chemists has been customarily addressed to catalyst activity, regio and stereospecificity. Nowadays, the impact of catalyst systems on other aspects of a chemical process has to be taken in due account, in relation to the increased cost of raw materials and energy. After showing the incidence of materials, utilities, manpower, investment on the production cost of a high density polyethylene process (typical representative of plastics) and of a high cis polybutadiene process (typical representative of a synthetic rubber), the potential impact of the catalyst system on the different cost items is pointed out. as an example, the possible economic advantages of new polymerization catalysts based on actinides and lanthanides are illustrated with reference to an improved high cis polybutadiene process. As a conclusion, the necessity of an even more strict cooperation between scientist investigating new organometallics and catalysts and, on the other side, process technologies and engineers is pointed out. Only by an early cooperation of this type can the advantages offered by 4 and 5f groups transition metals be transferred to improved industrial process and some development mishap can be avoided.

Thermodynamic review and calculations—alkali-metal oxide systems with nuclear fuels, fission products, and structural materials

This paper considers the phase equilibria of alkali metal oxides and their combinations with other oxides relevant to nuclear fuels, fission products, and structural materials. The other oxides include those of the lanthanides, the actinides, iron, nickel, aluminum, silicon, as well as those of periodic table groups IIA, IVB, VB, VIB, and VIA. The alkali metal halides, chalcogenides, and hydroxides are also included. Techniques are developed to permit calculation of phase equilibria and Ellingham diagrams in ternary and higher-order systems. These techniques include estimation of previously unknown 298.15 K values of the enthalpies of formation and the entropies of many compounds.

Mode of Action of Lithium

This communication will review some of the properties of lithium and four possible cellular sites of interaction between lithium and other cations. It will emphasize the observation that lithium interacts with cyclic adenosine monophosphate (AMP)-mediated processes and, finally, will review a hypothesis that the onset of mania may be associated with the development of supersensitivity of catecholamine receptors. New evidence will be reported that lithium can block the development of supersensitivity in CNS neuronal receptors in rats. PHYSICOCHEMICAL AND TRANSPORT CONSIDERATIONS The major properties of lithium that determine its actions are size, charge, electrical field density, and energy of hydration. Lithium is the smallest alkali ion. It has the largest electrical field density at its surface and therefore has the largest energy of hydration (energy required to strip off water molecules). Lithium shares many properties with other periodic table group I as well as some group II metals. It competes with four cations most abundant in biological tissue (Na

On the mechanism of the electrochemical reduction of TcO 4 −1 ion on platinum cathode in sulphuric acid solutions

Electroreduction of oxygen-containing anions of the elements of VII group of periodic table, in particular, technetium is a very complicated process. The structure of electron shells of technetium 4d6 5s1 (s9/2), allows some oxidation states from +7 to −1, and shows the tendency to hydrolysis, disproportionation and to complex formation. Heptavalent state with d0-electron configuration and low tendency to reduction is characteristic for technetium and rhenium. We have studied the products of electroreduction of ion TcO 4 − from sulphurous acid solutions of pertechnetate on platinum cathode using electrophoresis, methods of classic preparation chemistry, electron and vibratory spectroscopy. As a result we have succeeded in the isolation of the products of electrochemical reactions, identification and explaining some features of the process connected with the formation of metalic technetium and intermediate complex forms of reduced technetium.

The C (2 Π)→X(2Σ+) transition in thermal emission spectra of the diatomic alkaline earth bromides) transition in thermal emission spectra of the diatomic alkaline earth bromides

The extensive thermal emission spectrum attributed to the diatomic bromides of calcium, strontium and barium has been observed in the visible region at temperatures about 2200–2400° C, using a vacuum graphite furnace. Many new bands,viz., 141 in CaBr, 53 in SrBr and 68 in BaBr, have been recorded and classified. The vibrational constants agree with those determined by earlier workers and involved the ground state in each case. The transition C→X apears in each molecule and consists of two equally intense systems,viz., C1→X and C2→X. The general spectroscopic features of the C→X systems of the bromides of the II A sub group of the periodic table have been compared. They exhibit a close structural similarity and furnish a good example of homologous spectra. The system C→X in all these molecules arises from a C2 π−X2 Σ + transition where the2 π state appears to be intermediate between Hund’s cases (a) and (b).