A chart of consecutive sets of electronic orbits within atoms of chemical elements

2009

Angew Chem Int Ed

A closer look: A deeper theoretical understanding of the multifaceted periodic system of elements (PSE) has been achieved in recent years. The large energy gaps above the noble gas shells 1s(2) and np(6) (n=2-6) impress periodicity onto the whole PSE, which is complete with Period 7. The electron configurations of unbound atoms are chemically misleading. The common n+l rule is an example of the "invention of facts" even in the hard sciences.

Section: The Ao Sequence In Textbooksmentioning

confidence: 97%

Icon of Chemistry: The Periodic System of Chemical Elements in the New Century

Wang

2009

Angew Chem Int Ed

“…The respective orbital order can also be explained qualitatively, but should not be used as the common rule. The fashionable (n þ l) Madelung rule (Karapetoff 1930;Madelung 1936) refers only to groups 1 and 2. In all other groups, in particular in the cations, ''(n + 1)s is always above nd'' (Pilar, 1978), though not really always (Carlton, 1979)!…”

Section: Energetic Order Of Atomic Valence Orbitalsmentioning

confidence: 99%

Recommended Questions on the Road towards a Scientific Explanation of the Periodic System of Chemical Elements with the Help of the Concepts of Quantum Physics

2006

Found Chem

Periodic tables (PTs) are the 'ultimate paper tools' of general and inorganic chemistry. There are three fields of open questions concerning the relation between PTs and physics: (i) the relation between the chemical facts and the concept of a periodic system (PS) of chemical elements (CEs) as represented by PTs; (ii) the internal structure of the PS; (iii) The relation between the PS and atomistic quantum chemistry. The main open questions refer to (i). The fuzziness of the concepts of chemical properties and of chemical similarities of the CE and their compounds guarantees the autonomy of chemistry. We distinguish between CEs, Elemental Stuffs and Elemental Atoms. We comment on the basic properties of the basic elements. Concerning (ii), two sharp physical numbers (nuclear charge and number of valence electrons) and two coarse fuzzy ranges (ranges of energies and of spatial extensions of the atomic orbitals, AOs) characterize the atoms of the CEs and determine the two-dimensional structure of the PS. Concerning (iii), some relevant 'facts' about and from quantum chemistry are reviewed and compared with common 'textbook facts'. What counts in chemistry is the whole set of nondiffuse orbitals in low-energy average configurations of chemically bonded atoms. Decisive for the periodicity are the energy gaps between the core and valence shells. Diffuse Rydberg orbitals and minute spin-orbit splittings are important in spectroscopy and for philosophers, but less so in chemical science and for the PS.

“…One has to learn the (n+t,n) or so-called Madelung (1936) or Goudsmit rule, first published by Karapetoff (1930). It postulates the following order of AO levels, which is different from, but really not intermediate between the orders (1) and (2a) or (2b), as it should be: 1 s<2s<2p<3 s<3p<4s<3d<4p<5 s<4d<5p<6s<4 f<5d<6p<7 s<5f<6d ... (3) Ostrovsky (2001, 2003a, 2003b, 2004a) has recently reviewed the history of that very rule and its derivation from an approximation to the Thomas-Fermi effective one-electron potential.…”

Section: Madelung's Rule and The Pt: Contradictionsmentioning

confidence: 99%

Towards a Physical Explanation of the Periodic Table (PT) of Chemical Elements

Fundamental World of Quantum Chemistry

2004

A significant body of physical, mathematical and chemical knowledge has been accumulated in the past decades that forms the starting point for our task. The appropriate questions are here formulated. If one wants to explain the Periodic Table (PT) of chemical elements with physical theory, i.e. quantum chemically, one should at first elucidate the basic principles of the PT. It is based on 3 concepts, i) the linear arrangement of elements according to the nuclear charge number, ii) the partitioning of this array in order to create a two-dimensional map, and iii) the organization of this map so that chemically similar elements appear in neighborhoods, in particular in vertical columns. The PT has physical, mathematical and chemical aspects. From the chemical point of view, a two-sided criterion seems particularly relevant for the structure of the PT. On the empirical stoichiometric side, there are the same 'highest chemical valence numbers' within many of the groups of the PT. On the quantum theoretical side, there are the same 'numbers of valence electrons' (defined as separated from the 'atomic cores' on a chemically relevant energy scale), which are housed in similar sets of near-degenerate shells of 'valence atomic orbitals (AO)'. Therefore it is quantum chemically most essential to understand i) the emergence of a comparatively large gap between the highest ns 2 np6 core shell and the near-degenerate (n+l)s andlor (n+l)p,nd,(n-l)fvalence sub-shells, and ii) the numbers and types of orbitals above the cores available for valence activity. The specific energetic order of the optically active valence and Rydberg states, or the consequences of angular momentum couplings in unperturbed atoms, seem chemically less important. Authors of chemical textbooks and scholars interested in physical and philosophical aspects of the PT have often discussed chemically less relevant topics. In particular the (nH,n) or 'Madelung' rule postulating e.g. 3p<4s<3d as the energetic order of valence orbitals is chemically misleading. Valence (n+1)s AOs need not be considered at the qualitative level to explain most chemical transition metal phenomena or the alkali and alkaline earth cation compounds.