transition elements
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The current periodic table does not necessarily have a clear position for transition elements. Therefore, the purpose of this paper is to use the basic principle discovered by Mendeleev as it is and to create a periodic table with consistency for transition elements. By setting some hypotheses, it was found that transition elements also have regular periodicity, so we succeeded in clarifying the energy level of electrons in each orbit. In addition, by utilizing its periodicity, the electron configuration for each orbit was predicted for unknown elements. In this paper, we did not take the conventional idea of electron orbitals, that is, the idea of forming a hybrid orbital, but assumed a new orbital. Since the state in which electrons fit in orbits and stabilize is defined as an octet, this idea was used as the basic principle in this paper, but the hypothesis that "there are only three orbits in each shell" was established and verified. The calculation of the energy level of the electrons on the orbit became extremely easy, and the order of each orbit could be clarified. It was also found that the three-dimensional structure of the molecule may be visualized by paying attention to the valence electrons of the outermost shell of the element and the octet of the stability condition. Therefore, in this paper, by slightly expanding the structural formula of Kekulé, it became possible to easily determine whether or not the molecule synthesized by the bond between elements is stable. In addition, it has become possible to predict the three-dimensional structure of the molecule as well. Furthermore, not only will it be easier for students studying chemistry to understand complex chemical reactions, but it will also be useful for researchers in the development and research of new drugs.


BMC Chemistry ◽  
2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Violet M. Nkwe ◽  
Damian C. Onwudiwe ◽  
Mayowa A. Azeez

Abstract Background A large volume of dye molecules finds its way into the environment, accumulates in water bodies, and makes the aquatic system unsafe to human health. Due to the complex nature of these dye materials, most of the conventional techniques are not effective for their removal. Semiconductor photocatalysis has emerged as a promising technique for  the destruction of organic pollutants under UV or visible light irradiation. Among the semiconductors, Bi2S3 is widely employed in photocatalysis due to its non-toxicity and chemical stability. However, one of its problems is the high recombination rate of the charge, and various methods have been employed to enhance the photo-reactivity. One of  these methods is the incorporation of transition elements. Results Herein, a facile solvothermal method was used to prepare Bi2S3 nanorods and needle- shaped Sn doped Bi2S3, using bismuth(III) tris(N-phenyldithiocarbamate) as a single-source precursor. The prepared nanomaterials were characterized, and used as efficient photocatalyst for the photo enhanced degradation of methylene blue (MB) dye under visible light irradiation. The nanomaterials exhibited very good photocatalytic activity towards the photo degradation of MB, showing a degradation rate of up to 83% and 94% within 150 min for the pristine and Sn doped Bi2S3,  respectively. Conclusion The enhancement in the photocatalytic activity of the Sn doped Bi2S3 was attributed to the suppression in the recombination rate of the electron‐hole pairs, due to the formation of new energy level below the CB, that was capable of altering the equilibrium concentration of the carrier. This confirmed that Sn doped Bi2S3 could be utilized as valuable cost-efficient catalysts for eliminating methyl blue from aqueous solutions and also possible candidates in environmental pollution treatment.


2021 ◽  
Vol 387 ◽  
pp. 114145
Author(s):  
S. Eisenträger ◽  
J. Eisenträger ◽  
H. Gravenkamp ◽  
C.G. Provatidis

Author(s):  
Dipangkar Kalita ◽  
Mahesh Ram ◽  
Nihal Limbu ◽  
Atul Saxena

Abstract Investigation of structural, dynamical, mechanical, electronic and thermodynamic properties of RuYAs (Y = Cr and Fe) alloys have been performed from the first principle calculations. Among the three structural phases, ‘α’ phase is found to be energetically favorable for both the RuCrAs and RuFeAs compounds. The computed cohesive energies and phonon dispersion spectra indicate the structural and dynamical stabilities of both the compounds. Mechanical stability of these compounds are studied using elastic constants. The Pugh’s ratio predicts RuFeAs to be more ductile than RuCrAs. The RuCrAs alloy, on the other hand, is found to be a stiffer, harder and highly rigid crystal with stronger bonding forces than the RuFeAs. Furthermore, the thermodynamical properties have also been estimated with respect to the temperature under different pressures using the quasi-harmonic Debye model. In order to account for the effect of the highly correlated d transition elements in the system we incorporated the GGA+U approximations. Within the GGA+U approach, the electronic structure reveals the half-metallicity for both compounds, which follows the Slater-Pauling rule. The charge density and electron localized function reflect the covalent bonding among the constituent atoms. Bader analysis reveals that the charge transfer takes place from Cr/Fe to Ru and As atoms in both approximations. Both Raman and infrared active modes have been identified in the compounds.


2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Kaixuan Chen ◽  
Wan-Lu Li ◽  
W. H. Eugen Schwarz

Abstract The electron configurations of Ca, Zn and the nine transition elements M in between (and their heavier homologs) are reviewed on the basis of density functional theory and experimental facts. The d-s orbital energy and population patterns are systematically diverse. (i) The dominant valence electron configuration of most free neutral atoms M0 of groups g = 2–12 is 3d g−2 4s 2 (textbook rule), or 3d g−14s 1. (ii) Formal M q+ cations in chemical compounds have the dominant configuration 3d g−q 4s 0 (basic concept of transition metal chemistry). (iii) M0 atoms in metallic phases [M∞] of hcp, ccp(fcc) and bcc structures have intermediate populations near 3d g−1 4s 1 (lower d populations for Ca (ca. ½) and Zn (ca. 10)). Including the 4p valence orbitals, the dominant metallic configuration is 3d g−δ 4(sp) δ with δ ≈ 1.4 (±0.2) throughout (except for Zn). (iv) The 3d,4s population of atomic clusters M m varies for increasing m smoothly from single-atomic 3d g−24s 2 toward metallic 3d g−14s 1. – The textbook rule for the one-electron energies, i.e., ns < (n−1)d, holds ‘in a broader sense’ for the s block, but in general not for the d block, and never for the p block. It is more important to teach realistic atomic orbital (AO) populations such as the ones given above.


Author(s):  
Nobuya Banno ◽  
Kensuke Kobayashi ◽  
Akira Uchida ◽  
Hitoshi Kitaguchi

AbstractFor more than 30 years, Pb–Bi alloy and Wood's metal (50% Bi, 26.7% Pb, 13.3% Sn, and 10% Cd) have been used as representative superconducting solder intermedia to establish superconducting joints between NbTi and Nb3Sn wires in high-field nuclear magnetic resonance magnet systems. However, the use of Pb and Cd has been severely restricted by environmental regulations, such as the Restriction of Hazardous Substances Directive. Herein, a novel method of forming a superconducting joint between NbTi and Nb3Sn wires without Pb and Cd has been proposed. This approach is based on metallurgical bonding processes using a superconducting Nb-alloy intermedium, whose fine microstructure is maintained even after exposure to temperatures higher than 650 °C. Further, fine crystal defects become sources of magnetic flux pinning centers. Among transition elements close to Nb, Hf is considered the most suitable additive for realizing high-temperature-tolerable (HTT) superconducting Nb-alloy intermedia. Utilizing the HTT characteristic of Nb–Hf, a superconducting joint between Nb3Sn filaments and one end of the Nb–Hf alloy core was created by forming a superconducting Nb3Sn layer at the interface through a chemical reaction. The other end of the Nb–Hf alloy core was cold-pressed with NbTi filaments, to connect their active new surfaces to each other in order to create a superconducting joint. Ultimately, a superconducting joint between NbTi and Nb3Sn wires was realized with a high critical magnetic field (Bc2) of more than 1 T. The formation of the superconducting joint was confirmed by current decay measurements. This method of forming a superconducting joint is promising for application in environmentally friendly nuclear magnetic resonance magnet systems. Graphical abstract


Antioxidants ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1515
Author(s):  
Ming-Cheng Lin ◽  
Chien-Chi Liu ◽  
Yu-Chen Lin ◽  
Chin-Sheng Liao

Cerebral ischemia is related to increased oxidative stress. Resveratrol displays anti-oxidant and anti-inflammatory properties. The transition elements iron (Fe) and copper (Cu) are indispensable for the brain but overload is deleterious to brain function. Aluminum (Al) and arsenic (As) are toxic metals that seriously threaten brain health. This study was conducted to elucidate the correlation of the neuroprotective mechanism of resveratrol to protect cerebral ischemic damage with modulation of the levels of lipid peroxidation, anti-oxidants, transition elements, and toxic metals. Experimentally, 20 mg/kg of resveratrol was given once daily for 10 days. The cerebral ischemic operation was performed via occlusion of the right common carotid artery together with the right middle cerebral artery for 60 min followed by homogenization of the brain cortex and collection of supernatants for biochemical analysis. In the ligation group, levels of malondialdehyde, Fe, Cu, Al, and As increased but those of the anti-oxidants superoxide dismutase and catalase decreased. Pretreating rats with resveratrol before ischemia significantly reversed these effects. Our findings highlight the association of overload of Fe, Cu, As, and Al with the pathophysiology of cerebral ischemia. In conclusion, resveratrol protects against cerebral ischemic injury via restraining lipid peroxidation, transition elements, and toxic metals, but increasing anti-oxidant activity.


2021 ◽  
pp. 173-384
Author(s):  
Jürgen Kübler

The fundamental magnetic properties of iron, cobalt, and nickel are the center of interest, beginning with historical attempts and Stoner’s theory. Stoner susceptibility is derived in a modern way by Janak finding that only those three carry a magnetic moment in elementary metals. The energy-band structures of all transition elements are connected with their repective phase stability which is obtained by means of density-functional calculations. The band structure of the ferromagnetic metals is obtained and compared with angle-resolved photoemission data. The electronic structure of the antiferromagnetic metals, Cr, Mn, and fcc Fe is clarified. Next, the magnetic moments of transition-metal compounds are classified by means of the Slater–Pauling curve and a large number of compounds are half-metallic supplying spin-polarized transport. Multilayers realize oscillatory exchange and show unusual electronic properties such as giant magnetoresistance which is discussed in detail. Tunnel junctions supply spin valves. Relativistic effects in solids are of importance for magnetocrystalline anisotropy and spectroscopic effects. Kubo theory supplies the basic understanding of the magneto-optical Kerr effect for which a number of examples are given. Noncollinear magnetic order reveals novel interaction mechanisms, such as the Dzyaloshinsky–Moriya interaction. The Berry phase explains the anomalous Hall effect as well as the Nernst effect and leads to the field of topology in the solid state. Weyl fermions are also explored.


2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Katharina Eickmeier ◽  
Simon Steinberg

Abstract Understanding electronic structures is important in order to interpret and to design the chemical and physical properties of solid-state materials. Among those materials, tellurides have attracted an enormous interest, because several representatives of this family are at the cutting edge of basic research and technologies. Despite this relevance of tellurides with regard to the design of materials, the interpretations of their electronic structures have remained challenging to date. For instance, most recent research on tellurides, which primarily comprise post-transition elements, revealed a remarkable electronic state, while the distribution of the valence electrons in tellurides comprising group-I/II elements could be related to the structural features by applying the Zintl-Klemm-Busmann concept. In the cases of tellurides containing transition metals the applications of the aforementioned idea should be handled with care, as such tellurides typically show characteristics of polar intermetallics rather than Zintl phases. And yet, how may the electronic structure look like for a telluride that consists of a transition metal behaving like a p metal? To answer this question, we examined the electronic structure for the quaternary RbTbCdTe3 and provide a brief report on the crystal structures of the isostructural compounds RbErZnTe3 and RbTbCdTe3, whose crystal structures have been determined by means of X-ray diffraction experiments for the very first time.


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