1. Matter from the inside

2014 ◽  
pp. 1-21
Author(s):  
Peter Atkins
Keyword(s):  
Quantum Mechanics ◽  
General Structure ◽  
Valence Bond ◽  
Pauli Exclusion Principle ◽  
Exclusion Principle ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Covalent Bonds ◽  
Bond Theory

‘Matter from the inside’ shows that one way to understand how a physical chemist thinks and contributes to chemistry is to start at the atom's interior and then travel out into the world of bulk matter. It begins with the electronic structure of atoms, introduces the role of quantum mechanics in accounting for electron arrangement, and outlines Schrödinger's model of s-, p-, d-, and f-orbitals and the Pauli exclusion principle. Physical chemistry accounts for the general structure of the Periodic Table. The radius, ionization energy, and electron affinity properties of atoms are then considered along with ionic and covalent bonds, and the quantum mechanics of bonds, including valence-bond theory and molecular orbital theory.

The molecular orbital theory of chemical valency XIII. Orbital wave functions for excited states of a homonuclear diatomic molecule

1953 ◽  
Vol 216 (1126) ◽  
pp. 424-433 ◽  
Keyword(s):  
Molecular Orbital ◽  
Excited States ◽  
Valence Bond ◽  
Present Theory ◽  
Wave Functions ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Bond Theory ◽  
Homonuclear Diatomic Molecules ◽  
Approximate Wave

The expansions for the exact wave functions for excited states of homonuclear diatomic molecules derived in part XII are used as the basis for discussing various approximate wave functions of the orbital type. The states considered in detail are the lowest states of symmetries 1 Σ u + , 3 Σ u + . The calculus of variations is used to determine the optimum forms for the component orbital functions. A transformation to equivalent orbitals is used to bring out the physical significance of the various wave functions, and to relate the present theory to earlier theories, in particular the molecular orbital theory, the valence-bond theory and their generalizations.

Chemical Bonding 2: Modern Theories of Chemical Bonding

2021 ◽  
pp. 102-128
Author(s):  
Christopher O. Oriakhi
Keyword(s):  
Chemical Bonding ◽  
Valence Bond ◽  
Molecular Geometry ◽  
Electron Delocalization ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Valence Bond Theory ◽  
Electron Group ◽  
Bond Theory ◽  
Lewis Structures

Chemical Bonding II: Modern Theories of Chemical Bonding explains four bonding theories related to molecular geometry and bonding. Lewis structures and the Valence-Shell Electron-Pair Repulsion (VSEPR) model are used to describe and predict the electron group geometry, molecular geometry and shapes of molecules. The VSEPR model is then used to predict molecular polarity as a function of shape. This leads to Valence Bond Theory, which uses the principles of orbital overlap and hybridization of atomic orbitals to describe chemical bonding. Finally the Molecular Orbital Theory (MOT) based on electron delocalization is discussed in terms of bonding and anti-bonding molecular orbitals.

scholarly journals Valence Bond Theory—Its Birth, Struggles with Molecular Orbital Theory, Its Present State and Future Prospects

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1624
Author(s):  
Sason Shaik ◽  
David Danovich ◽  
Philippe C. Hiberty
Keyword(s):  
Molecular Orbital ◽  
Present State ◽  
Valence Bond ◽  
Molecular Orbital Theory ◽  
Future Prospects ◽  
Orbital Theory ◽  
Linus Pauling ◽  
Valence Bond Theory ◽  
Bond Theory ◽  
Mo Theory

This essay describes the successive births of valence bond (VB) theory during 1916–1931. The alternative molecular orbital (MO) theory was born in the late 1920s. The presence of two seemingly different descriptions of molecules by the two theories led to struggles between the main proponents, Linus Pauling and Robert Mulliken, and their supporters. Until the 1950s, VB theory was dominant, and then it was eclipsed by MO theory. The struggles will be discussed, as well as the new dawn of VB theory, and its future.

scholarly journals X rays on quantum mechanics: Pauli Exclusion Principle and collapse models at test

2015 ◽  
Vol 631 ◽  
pp. 012068 ◽  
Author(s):  
C Curceanu ◽  
S Bartalucci ◽  
A Bassi ◽  
S Bertolucci ◽  
C Berucci ◽  
...  
Keyword(s):  
Quantum Mechanics ◽  
Pauli Exclusion Principle ◽  
Exclusion Principle ◽  
X Rays ◽  
Collapse Models

scholarly journals VIP: AN EXPERIMENT TO SEARCH FOR A VIOLATION OF THE PAULI EXCLUSION PRINCIPLE

2007 ◽  
Vol 22 (02n03) ◽  
pp. 242-248 ◽  
Author(s):  
E. Milotti ◽  
S. Bartalucci ◽  
S. Bertolucci ◽  
M. Bragadireanu ◽  
M. Cargnelli ◽  
...  
Keyword(s):  
Quantum Mechanics ◽  
Basic Principle ◽  
Pauli Exclusion Principle ◽  
Experimental Results ◽  
Underground Laboratory ◽  
Exclusion Principle

The Pauli Exclusion Principle is a basic principle of Quantum Mechanics, and its validity has never been seriously challenged. However, given its fundamental standing, it is very important to check it as thoroughly as possible. Here we describe the VIP (VIolation of the Pauli exclusion principle) experiment, an improved version of the Ramberg and Snow experiment (E. Ramberg and G. Snow, Phys. Lett. B238, 438 (1990)); VIP has just completed the installation at the Gran Sasso underground laboratory, and aims to test the Pauli Exclusion Principle for electrons with unprecedented accuracy, down to β2/2 ≈ 10-30 - 10-31. We report preliminary experimental results and briefly discuss some of the implications of a possible violation.

Quantum Mechanics and the Periodic Table

2019 ◽  
Author(s):  
Eric Scerri
Keyword(s):  
Quantum Mechanics ◽  
Quantum Theory ◽  
Periodic Table ◽  
Chemical Properties ◽  
Pauli Exclusion Principle ◽  
Niels Bohr ◽  
Exclusion Principle ◽  
Old Quantum Theory ◽  
Set Up ◽  
Three Body

In chapter 7, the influence of the old quantum theory on the periodic system was considered. Although the development of this theory provided a way of reexpressing the periodic table in terms of the number of outer-shell electrons, it did not yield anything essentially new to the understanding of chemistry. Indeed, in several cases, chemists such as Irving Langmuir, J.D. Main Smith, and Charles Bury were able to go further than physicists in assigning electronic configurations, as described in chapter 8, because they were more familiar with the chemical properties of individual elements. Moreover, despite the rhetoric in favor of quantum mechanics that was propagated by Niels Bohr and others, the discovery that hafnium was a transition metal and not a rare earth was not made deductively from the quantum theory. It was essentially a chemical fact that was accommodated in terms of the quantum mechanical understanding of the periodic table. The old quantum theory was quantitatively impotent in the context of the periodic table since it was not possible to even set up the necessary equations to begin to obtain solutions for the atoms with more than one electron. An explanation could be given for the periodic table in terms of numbers of electrons in the outer shells of atoms, but generally only after the fact. But when it came to trying to predict quantitative aspects of atoms, such as the ground-state energy of the helium atom, the old quantum theory was quite hopeless. As one physicist stated, “We should not be surprised . . . even the astronomers have not yet satisfactorily solved the three-body problem in spite of efforts over the centuries.” A succession of the best minds in physics, including Hendrik Kramers, Werner Heisenberg, and Arnold Sommerfeld, made strenuous attempts to calculate the spectrum of helium but to no avail. It was only following the introduction of the Pauli exclusion principle and the development of the new quantum mechanics that Heisenberg succeeded where everyone else had failed.

Quantum Constraints in π Systems: The Role of the Pauli Antisymmetry Principle for π Electronic Properties

1997 ◽  
Vol 52 (10) ◽  
pp. 717-726
Author(s):  
Michael C. Böhm ◽  
Johannes Schütt
Keyword(s):  
Hard Core ◽  
Pauli Exclusion Principle ◽  
Exclusion Principle ◽  
Nearest Neighbour ◽  
Charge Fluctuations ◽  
Fermionic Systems ◽  
Ring Atom ◽  
Quantum Statistical ◽  
The Many

Abstract It is demonstrated that the Pauli antisymmetry principle (PAP) is without influence in the π electron subspace of polyenes and (4n + 2) annulenes (n = 0, 1, 2...) as long as the hoppings are restricted to nearest-neighbour centers. Here the π electrons behave like a hard core bosonic (hcb) ensemble where fermionic on-site and bosonic intersite properties are combined. In 4n and (2n + 1) annulenes (n = 1,2, 3...) π electron jumps between the first and last ring atom lead to a Pauli antisymmetry-based destabilization. The second quantum constraint in fermionic systems is the Pauli exclusion principle (PEP). In the many-electron basis adopted in the present work it is possible to treat the PAP and PEP as two decoupled constraints. The electronic destabilization due to the PEP is enhanced with increasing size of the system. The influence of the PAP and PEP on the π electrons is discussed in terms of π energies and charge fluctuations. The model Hamiltonians adopted are of the Hückel molecular orbital (HMO) and Pariser-Parr-Pople (PPP) type. We suggest quantum statistical definitions of the quantities "aromaticity" and "antiaromaticity", qualitative descriptors which are widely employed in the chemical literature.

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