The periodic table and the physics that drives it

Schwerdtfeger, Peter; Smits, Odile R.; Pyykkö, Pekka

doi:10.1038/s41570-020-0195-y

Cited by 75 publications

(72 citation statements)

References 284 publications

(235 reference statements)

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“…As long as a classification system is beneficial to economy of description , to structuring knowledge [italics added] and to our understanding, and hard cases constitute a small minority, then keep it. If the system becomes less than useful, then scrap it and replace it with a system based on different shared characteristics.” In the case of hydrogen and helium, for example, we agree with the suggestion of Schwerdtfeger et al ( 2020 ): “Although hydrogen and helium are clearly separate from the rest of the PTE, almost every chemist agrees that we can leave these elements in their current place in the PTE, keeping their distinctive quantum nature in mind [italics added].”…”

Section: Different Representations Of Periodicity: Chemical Narrativesupporting

confidence: 85%

Understanding Periodic and Non-periodic Chemistry in Periodic Tables

et al. 2021

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The chemical elements are the “conserved principles” or “kernels” of chemistry that are retained when substances are altered. Comprehensive overviews of the chemistry of the elements and their compounds are needed in chemical science. To this end, a graphical display of the chemical properties of the elements, in the form of a Periodic Table, is the helpful tool. Such tables have been designed with the aim of either classifying real chemical substances or emphasizing formal and aesthetic concepts. Simplified, artistic, or economic tables are relevant to educational and cultural fields, while practicing chemists profit more from “chemical tables of chemical elements.” Such tables should incorporate four aspects: (i) typical valence electron configurations of bonded atoms in chemical compounds (instead of the common but chemically atypical ground states of free atoms in physical vacuum); (ii) at least three basic chemical properties (valence number, size, and energy of the valence shells), their joint variation across the elements showing principal and secondary periodicity; (iii) elements in which the (sp)8, (d)10, and (f)14valence shells become closed and inert under ambient chemical conditions, thereby determining the “fix-points” of chemical periodicity; (iv)peculiar elements at the top and at the bottom of the Periodic Table. While it is essential that Periodic Tables display important trends in element chemistry we need to keep our eyes open for unexpected chemical behavior in ambient, near ambient, or unusual conditions. The combination of experimental data and theoretical insight supports a more nuanced understanding of complex periodic trends and non-periodic phenomena.

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Section: Different Representations Of Periodicity: Chemical Narrativesupporting

confidence: 85%

Understanding Periodic and Non-periodic Chemistry in Periodic Tables

et al. 2021

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“…These superheavy elements show very unusual behavior compared to their lighter congeners due to strong relativistic effects. [8][9][10] For example Cn and Fl are predicted to be chemically inert [7,11,12] due to the relativistic 7s shell contraction for Cn and the large spin-orbit splitting of the 7p shell, resulting in a closed 7p 1/2 shell for Fl.…”

mentioning

confidence: 99%

Oganesson: A Noble Gas Element That Is Neither Noble Nor a Gas

et al. 2020

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Oganesson (Og) is the last entry into the Periodic Table completing the seventh period of elements and group 18 of the noble gases. Only five atoms of Og have been successfully produced in nuclear collision experiments, with an estimate half‐life for 0pt2.84526pt2942.84526pt118 Og of 0.69+0.64-0.22 ms.[1] With such a short lifetime, chemical and physical properties inevitably have to come from accurate relativistic quantum theory. Here, we employ two complementary computational approaches, namely parallel tempering Monte‐Carlo (PTMC) simulations and first‐principles thermodynamic integration (TI), both calibrated against a highly accurate coupled‐cluster reference to pin‐down the melting and boiling points of this super‐heavy element. In excellent agreement, these approaches show Og to be a solid at ambient conditions with a melting point of ≈325 K. In contrast, calculations in the nonrelativistic limit reveal a melting point for Og of 220 K, suggesting a gaseous state as expected for a typical noble gas element. Accordingly, relativistic effects shift the solid‐to‐liquid phase transition by about 100 K.

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“…(13) is ignored, the contribution to ELF from the spin-current tensor density J is expected to be nonzero in relativistic superheavy atoms. For instance, the spin-orbit splitting for the valence 7p orbital of the element Og (Z = 118) is predicted to be very large, around 10 eV [14,73]. While Og is believed to be a spin-saturated system (the whole 7p shell is filled), this is not the case for, e.g., Fl (Z = 114, 7p 3/2 shell empty) for which J and the resulting spin-orbit current should be consider when analyzing the corresponding ELF.…”

Section: Discussionmentioning

confidence: 99%

Nucleon localization function in rotating nuclei

Chen

Zhang

et al. 2020

Phys. Rev. C

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Background: An electron localization function was originally introduced to visualize in positional space bond structures in molecules. It became a useful tool to describe electron configurations in atoms, molecules, and solids. In nuclear physics, a nucleon localization function (NLF) has been used to characterize cluster structures in light nuclei, formation of fragments in fission, and pasta phases appearing in the inner crust of neutron stars. Purpose: We use the NLF to study the nuclear response to fast rotation. Methods: We generalize the NLF to the case of nuclear rotation. The extended expressions involve both timeeven and time-odd local particle and spin densities and currents. Since the current density and density gradient contribute to the NLF primarily at the surface, we propose a simpler spatial measure given by the kinetic-energy density. Illustrative calculations for the superdeformed yrast band of 152 Dy were carried out by using the cranked Skyrme-Hartree-Fock method. We also employed the cranked harmonic-oscillator model to gain insights into spatial patterns revealed by the NLF at high angular momentum. Results: In the case of a deformed rotating nucleus, several NLFs can be introduced, depending on the definition of the spin-quantization axis, direction of the total angular momentum, and self-consistent symmetries of the system. Contributions to the NLF from the current density, spin-current tensor density, and density gradient terms are negligible in the nuclear interior. The oscillating pattern of the simplified NLF can be explained in terms of a constructive interference between kinetic-energy and particle densities. The characteristic nodal pattern seen in the NLF in the direction of major axis of a rotating nucleus comes from single-particle orbits carrying large aligned angular momentum. The variation of the NLF along the minor axis of the nucleus can be traced back to deformation-aligned orbits. Conclusions: The NLF allows a simple interpretation of the shell structure evolution in the rotating nucleus in terms of the angular-momentum alignment of individual nucleons. We expect that the NLF will be very useful for the characterization and visualization of other collective modes in nuclei and time-dependent processes.

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The periodic table and the physics that drives it

Cited by 75 publications

References 284 publications

Understanding Periodic and Non-periodic Chemistry in Periodic Tables

Understanding Periodic and Non-periodic Chemistry in Periodic Tables

Oganesson: A Noble Gas Element That Is Neither Noble Nor a Gas

Nucleon localization function in rotating nuclei

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