* Valence bond programs.

* Chemistry: Molecular theory — Kinetic theory of gases — Molecular orbital theory — Valence bond theory — Transition state theory — RRKM theory — Chemical graph theory — Flory-Huggins solution theory — Marcus theory — Lewis theory ( successor to Brønsted – Lowry acid – base theory ) — HSAB theory — Debye – Hückel theory — Thermodynamic theory of polymer elasticity — Reptation theory — Polymer field theory — Møller – Plesset perturbation theory — Density Functional Theory — Frontier molecular orbital theory — Polyhedral skeletal electron pair theory — Baeyer strain theory — Quantum theory of atoms in molecules — Collision theory — Ligand field theory ( successor to Crystal field theory ) — Variational Transition State Theory — Benson group increment theory — Specific ion interaction theory

Valence bond theory gives us a model for benzene where each carbon atom makes two sigma bonds with its neighbouring carbon atoms and one with a hydrogen atom.

Four covalent bond s. Carbon has four valence electrons and here a Valence ( chemistry ) | valence of four.

Valence electrons can determine the element's chemical properties and if it will bond with others or not.

According to Charles Coulson, author of the noted 1952 book Valence, this period marks the start of " modern valence bond theory ", as contrasted with older valence bond theories, which are essentially electronic theories of valence couched in pre-wave-mechanical terms.

Valence bond theory considers that the overlapping atomic orbitals of the participating atoms form a chemical bond.

Valence bond theory views bonds as weakly coupled orbitals ( small overlap ).

Valence bond theory is typically easier to employ in ground state molecules.

Valence bond theory now complements molecular orbital ( MO ) theory, which does not adhere to the VB idea that electron pairs are localized between two specific atoms in a molecule but that they are distributed in sets of molecular orbitals which can extend over the entire molecule.

Valence bond theory views aromatic properties of molecules as due to resonance between Kekulé, Dewar and possibly ionic structures, while molecular orbital theory views it as delocalization of the π-electrons.

# REDIRECT Chemical bond # Valence bond theory

Valence bond theory concerns itself with the formation of sigma and pi bonds.

# REDIRECT Valence bond theory

The books that were influential in the early development of computational quantum chemistry include Linus Pauling and E. Bright Wilson's 1935 Introduction to Quantum Mechanics – with Applications to Chemistry, Eyring, Walter and Kimball's 1944 Quantum Chemistry, Heitler's 1945 Elementary Wave Mechanics – with Applications to Quantum Chemistry, and later Coulson's 1952 textbook Valence, each of which served as primary references for chemists in the decades to follow.

* Valence ( chemistry )

* Valence shell in chemistry

* Valence ( chemistry ).

* Generalized Valence Bond, a method in computational chemistry

* Valence ( chemistry )

# redirect Valence ( chemistry )

Valence shell electron pair repulsion ( VSEPR ) rules are a model in chemistry used to predict the shape of individual molecules based upon the extent of electron-pair electrostatic repulsion.

# redirect Valence ( chemistry )

# redirect Valence ( chemistry )

Bonding usually discussed in the context of molecular orbital theory, which recognizes the triple bond as arising from overlap of s and p orbitals.

In the language of valence bond theory, the carbon atoms in an alkyne bond are sp hybridized: they each have two unhybridized p orbitals and two sp hybrid orbitals.

Clinton's advisers pressured him to raise taxes on the theory that a smaller federal budget deficit would reduce bond interest rates.

Lewis theory explains that an acid is a substance which is capable of accepting a pair of electrons from another substance during the process of bond formation, while a base is a substance which can provide a pair of electrons to form a new bond.

More sophisticated theories are valence bond theory which includes orbital hybridization and resonance, and the linear combination of atomic orbitals molecular orbital method which includes ligand field theory.

The Heitler-London method forms the basis of what is now called valence bond theory.

This molecular orbital theory represented a covalent bond as an orbital formed by combining the quantum mechanical Schrödinger atomic orbitals which had been hypothesized for electrons in single atoms.

Most quantitative calculations in modern quantum chemistry use either valence bond or molecular orbital theory as a starting point, although a third approach, Density Functional Theory, has become increasingly popular in recent years.

In 1927, valence bond theory was formulated and it argues that a chemical bond forms when two valence electrons, in their respective atomic orbitals, work or function to hold two nuclei together, by virtue of effects of lowering system energies.

In this paper, elaborating on the works of Lewis, and the valence bond theory ( VB ) of Heitler and London, and his own earlier works, Pauling presented six rules for the shared electron bond, the first three of which were already generally known:

Since the 1980s, the more difficult problems of implementing valence bond theory into computer programs have been solved largely, and valence bond theory has seen a resurgence.

In some respects valence bond theory is superior to molecular orbital theory.

When applied to the simplest two-electron molecule, H < sub > 2 </ sub >, valence bond theory, even at the simplest Heitler-London approach, gives a much closer approximation to the bond energy, and it provides a much more accurate representation of the behavior of the electrons as chemical bonds are formed and broken.

The concepts of hybridization are so versatile, and the variability in bonding in most organic compounds is so modest, that valence bond theory remains an integral part of the vocabulary of organic chemistry.

The deficiencies of valence bond theory became apparent when hypervalent molecules ( e. g. PF < sub > 5 </ sub >) were explained without the use of d orbitals that were crucial to the bonding hybridisation scheme proposed for such molecules by Pauling.

In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond.

In particular, chemistry studies interactions between atoms, and chemical bond s.

Modern calculations in quantum chemistry usually start from ( but ultimately go far beyond ) a molecular orbital rather than a valence bond approach, not because of any intrinsic superiority in the former but rather because the MO approach is more readily adapted to numerical computations.

In simple chemistry, as per valence bond theory, the carbon atom must follow the " 4-hydrogen rule ", which states that the maximum number of atoms available to bond with carbon is equal to the number of electrons that are attracted into the outer shell of carbon. In terms of shells, carbon consists of an incomplete outer shell, which comprises 4 electrons, and thus has 4 electrons available for covalent or dative bonding.

The H – H bond is one of the strongest bonds in chemistry, with a bond dissociation enthalpy of 435. 88 kJ / mol at 298 K. As a consequence of this strong bond, H < sub > 2 </ sub > dissociates to only a minor extent until higher temperatures.

Inorganic compounds show rich variety: A: Diborane features Three-center two-electron bond | unusual bonding B: Caesium chloride has an archetypal crystal structure C: Cyclopentadienyliron dicarbonyl dimer | Fp < sub > 2 </ sub > is an Organometallic chemistry | organometallic complex D: Polydimethylsiloxane | Silicone's uses range from breast implant s to Silly Putty E: Grubbs ' catalyst won the Nobel Prize in Chemistry | 2005 Nobel Prize for Robert H. Grubbs | its discoverer F: Zeolite s find extensive use as molecular sieve s G: Copper ( II ) acetate surprised Theoretical chemistry | theoreticians with its diamagnetism

The study of molecules by molecular physics and theoretical chemistry is largely based on quantum mechanics and is essential for the understanding of the chemical bond.

The extremely strong bond in elemental nitrogen dominates nitrogen chemistry, causing difficulty for both organisms and industry in breaking the bond to convert the into useful compounds, but at the same time causing release of large amounts of often useful energy when the compounds burn, explode, or decay back into nitrogen gas.

Resonance ( chemistry ) | Resonance structures of the peptide bond that links individual amino acids to form a protein polymer

Predicting the properties of chemical compounds from a description of atoms and how they bond is one of the major goals of physical chemistry.

Lipscomb has worked in three main areas, nuclear magnetic resonance and the chemical shift, boron chemistry and the nature of the chemical bond, and large biochemical molecules.

Kathleen Lonsdale's 1928 structure of hexamethylbenzene established the hexagonal symmetry of benzene and showed a clear difference in bond length between the aliphatic C – C bonds and aromatic C – C bonds ; this finding led to the idea of resonance between chemical bonds, which had profound consequences for the development of chemistry.

The distance between two bonded atoms is a sensitive measure of the bond strength and its bond order ; thus, X-ray crystallographic studies have led to the discovery of even more exotic types of bonding in inorganic chemistry, such as metal-metal double bonds ,< ref > metal-metal quadruple bonds ,< ref > and three-center, two-electron bonds.

In chemistry, a disulfide bond ( Br. E.

The term dipolar bond is used in organic chemistry for compounds such as amine oxides for which the electronic structure can be described in terms of the basic amine donating two electrons to an oxygen atom.

It is called the strongest bond in organic chemistry.