The Valency Interaction Formula, or VIF provides a way of drawing or interpreting the molecular

structural formula The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are possibly arranged in the real three-dimensional space. The chemical bondi ...

based on

molecular orbital theory In chemistry, molecular orbital theory (MO theory or MOT) is a method for describing the electronic structure of molecules using quantum mechanics. It was proposed early in the 20th century. In molecular orbital theory, electrons in a molecule ...

. Valency Points, VP, dots drawn on a page, represent

valence orbital In chemistry and physics, a valence electron is an electron in the outer shell associated with an atom, and that can participate in the formation of a chemical bond if the outer shell is not closed. In a single covalent bond, a shared pair forms ...

s. Valency Interactions, VI, that connect the dots, show interactions between these valence orbitals. Theory was developed by Turkish quantum chemist

Oktay Sinanoğlu Oktay Sinanoğlu (February 25, 1935 – April 19, 2015) was an internationally renowned Turkish physical chemist and molecular biophysicist. Private life Sinanoğlu was born in Bari, Italy on February 25, 1935 to Nüzhet Haşim and Rüveyde (K ...

in the early 1980s and first published in 1983. The theory was like a new language of

quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...

by the exact definition of

Hilbert space In mathematics, Hilbert spaces (named after David Hilbert) allow generalizing the methods of linear algebra and calculus from (finite-dimensional) Euclidean vector spaces to spaces that may be infinite-dimensional. Hilbert spaces arise natural ...

. It was also the solution of the problem that

Paul Dirac Paul Adrien Maurice Dirac (; 8 August 1902 – 20 October 1984) was an English theoretical physicist who is regarded as one of the most significant physicists of the 20th century. He was the Lucasian Professor of Mathematics at the Univer ...

was trying to solve at the time of his death in 1984, which concerned the hidden symmetries in Hilbert space which were responsible for the accidental degeneracies not arising from a spatial symmetry, that was about the higher symmetries of Hilbert space) Sinanoğlu showed that the solution was possible only when the topology tool was used. This VIF theory also connected both delocalized and localized molecular orbital schemes into a unified form in an elegant way. Chemical deductions are made from a VIF picture with the application of two pictorial rules. These are

linear transformation In mathematics, and more specifically in linear algebra, a linear map (also called a linear mapping, linear transformation, vector space homomorphism, or in some contexts linear function) is a mapping V \to W between two vector spaces that pre ...

s applied to the VIF structural formula as a

quantum operator In physics, an operator is a function over a space of physical states onto another space of physical states. The simplest example of the utility of operators is the study of symmetry (which makes the concept of a group useful in this context). Beca ...

. Transformation by the two rules preserves invariants crucial to the characterization of the molecular electronic properties, the numbers of bonding, non-bonding, and

anti-bonding In chemical bonding theory, an antibonding orbital is a type of molecular orbital that weakens the chemical bond between two atoms and helps to raise the energy of the molecule relative to the separated atoms. Such an orbital has one or more No ...

orbitals and/or the numbers of doubly, singly, and unoccupied valence orbitals. The two pictorial rules relate all pictures with the same electronic properties as characterized by these invariants. A thorough presentation of VIF is available through the

open access journal Open access (OA) is a set of principles and a range of practices through which research outputs are distributed online, free of access charges or other barriers. With open access strictly defined (according to the 2001 definition), or libre op ...

''symmetry''.

References

Theoretical chemistry {{theoretical-chem-stub

See also

References