What are orbitals chemistry

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Understanding Orbitals in Chemistry

Introduction to Orbitals in Chemistry

Orbitals are fundamental concepts in chemistry, representing regions in an atom or molecule where electrons are likely to be found. These mathematical constructs are essential for describing the behavior and interaction of electrons, which in turn dictate the chemical properties and reactions of substances.

Molecular Orbitals and Chemical Properties

Molecular orbitals are particularly significant because they describe the multi-electron wavefunction of molecules. The highest-lying orbitals, known as the highest occupied molecular orbitals (HOMOs), are crucial as they are directly involved in chemical reactions and bonding . These orbitals can be experimentally observed and imaged using advanced techniques such as high harmonics generated from intense femtosecond laser pulses, allowing scientists to visualize the three-dimensional structure of orbitals and follow the dynamics of electron wave packets .

Energy Ordering and Real-World Analogues

The energy ordering of molecular orbitals is a key aspect of computational chemistry. Photoemission tomography studies have shown that while there are deviations in energy positions when compared to density functional calculations, the concept of molecular orbitals remains robust and experimentally observable . This reinforces the practical utility of orbitals in predicting and understanding chemical behavior.

Orbital Symmetry and Chemical Reactions

The theory of molecular orbitals also includes the concept of orbital symmetry, which is used to rationalize and predict the stereochemical outcomes of organic reactions. This qualitative approach, based on symmetry, overlap, and interaction of orbitals, has proven effective in explaining the electronic structure of stable molecules and the course of chemical reactions .

Chemical Orbital Theory

Chemical orbital theory extends the concept of orbitals to describe interactions at various levels, including atoms, bonds, and molecules. This theory categorizes interactions into two-orbital, three-orbital, and cyclic interactions, each contributing to the overall properties and reactivity of molecules. Key elements of this theory include phase and amplitude of orbitals, electron delocalization, and orbital symmetry .

Orbital Molecules in Solid-State Chemistry

In solid-state chemistry, orbital molecules are formed by coupled orbital states on metal ions within an ordered solid. These structures, such as spin-singlet dimers and more complex species like 18-electron heptamers, represent a new class of quantum electronic states in materials . These findings highlight the diverse applications of orbital theory beyond traditional molecular chemistry.

Atomic Orbitals and Bonding

Atomic orbitals are the building blocks for understanding chemical bonding. A rigorous definition of atomic orbitals, free from nucleus-centered basis functions, allows for a universal application across different electronic structure calculations. These atomic orbitals can be combined to accurately represent molecular orbitals and natural orbitals, providing a compact description of bonding in various chemical systems .

Conclusion

Orbitals are indispensable in the field of chemistry, providing a framework for understanding the behavior of electrons in atoms and molecules. From predicting chemical reactions to designing new materials, the study of orbitals continues to be a cornerstone of both theoretical and experimental chemistry. The ongoing advancements in imaging and computational techniques promise to further deepen our understanding of these fundamental constructs.

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Most relevant research papers on this topic

Tomographic imaging of molecular orbitals

This study successfully images the full three-dimensional structure of a single molecular orbital using high harmonics generated from intense femtosecond laser pulses, allowing for the attosecond dynamics of an electron wave packet.

Highly Cited

2004·

1680citations

·J. Itataniet al.

Nature

Energy Ordering of Molecular Orbitals

The energy ordering of molecular orbitals in PTCDA monolayers on Ag surfaces differs from density functional calculations, suggesting the importance of static electron correlation beyond local approximations.

2016·

37citations

·P. Puschniget al.

The Journal of Physical Chemistry Letters

Conservation of orbital symmetry

Chemistry remains an experimental science. The theory of chemical bonding leaves much to be desired. Yet, the past 20 years have been marked by a fruitful symbiosis of organic chemistry and molecular orbital theory. Of necessity this has been a marriage of poor theory with good experiment. Tentative conclusions have been arrived a t on the basis of theories which were such a patchwork on approximations that they appeared to have no right to work; yet, in the hands of clever experimentalists, these ideas were transformed into novel molecules with unusual properties. In the same way, by utilizing the most simple but fundamental concepts of molecular orbital theory we have in the past 3 years been able to rationalize and predict the stereochemical course of virtually every concerted organic reaction.' In our work we have relied on the most basic ideas of molecular orbital theory-the concepts of symmetry, overlap, interaction, bonding, and the nodal structure of wave functions. The lack of numbers in our discussion is not a weakness-it is its greatest strength. Precise numerical values would have to result from some specific sequence of approximations. But an argument from first principles or symmetry, of necessity qualitative, is in fact much stronger than the deceptively authoritative numerical result. For, if the simple argument is true, then any approximate method, as well as the now inaccessible exact solution, must obey it. The simplest description of the electronic structure of a stable molecule is that i t is characterized by a finite band of doubly occupied electronic levels, called bonding orbitals, separated by a gap from a corresponding band of unoccupied, antiboding levels as well as a continuum of higher levels. The magnitude of the gap may range from 40 kcal/mole for highly delocalized, large aromatic systems to 250 kcal/mole for saturated hydrocarbons. It should be noted in context that socalled nonbonding electrons of heteroatoms are in fact bonding. Consider a simple reaction of two molecules to give a third species, proceeding in a nonconcerted manner through a diradical intermediate I. A + B + [I] + C

Highly Cited

1968·

2545citations

·R. Hoffmannet al.

Accounts of Chemical Research

Elements of a chemical orbital theory.

Chemical orbital theory considers interactions of orbitals of atoms, bonds, and molecules, focusing on two-orbital interactions and introducing orbital mixing rules and orbital phase theory for cyclic interactions.

2010·

9citations

·S. Inagaki

Topics in current chemistry

Orbital molecules in electronic materials

Orbital molecules are a new class of quantum electronic states in solids, with diverse structures and properties in various transition metal oxides.

2015·

44citations

·J. Attfield

APL Materials

Orbitals in inorganic chemistry: metal rings and clusters, hydronitrogens, and heterocyles.

Chemical orbital theory helps understand and design inorganic molecules, including metal rings, clusters, hydronitrogens, and heterocyles.

2010·

3citations

·S. Inagaki

Topics in current chemistry

Concept of Orbital Entanglement and Correlation in Quantum Chemistry.

Quantum chemistry reveals that orbital entanglement is mainly classical, challenging the general significance of entanglement in chemical bonding.

2020·

53citations

·Lexin Dinget al.

Journal of chemical theory and computation

Atomic orbitals in molecules

This new definition of atomic orbitals in molecules (AOIMs) is universally applicable and provides a continuous and orthonormal representation of molecular orbitals and strongly occupied natural orbitals, making them suitable for compact description of bonding in diverse chemical systems.

1998·

11citations

·J. Cioslowskiet al.

Journal of Chemical Physics

Orbitals for Analyzing Bonding and Magnetism of Heavy-Metal Complexes

This paper presents a theoretical framework for using electron orbitals to analyze the electronic structure, chemical bonding, and magnetic properties of metal complexes from relativistic quantum chemical wavefunction calculations.

2016·

27citations

·J. Autschbach

Comments on Inorganic Chemistry

Inquiry-Based Activities and Games That Engage Students in Learning Atomic Orbitals.

Inquiry-based activities and a gamified approach can engage students in learning atomic orbitals, essential for understanding chemical bonding models and relationships.

2022·

10citations

·Xiao Liet al.

Journal of chemical education

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