Quantum chemistry

From Academic Kids

Quantum chemistry is the application of quantum mechanics to problems in chemistry. The description of the electronic behavior of atoms and molecules as pertains to their reactivity is an application of quantum chemistry. Quantum chemistry lies on the border between chemistry and physics, and significant contributions have been made by scientists from both branches of science.

The foundation of quantum chemistry is the wave model of the atom as a small dense positively charged nucleus surrounded by electrons. However, unlike the earlier Bohr model of the atom, the wave model describes electrons as "clouds" moving in orbitals, and their position is represented by a probablity distribution, rather than discrete points. The details of the distribution are caluclated from the Schrdinger equation. The strength of this model lies in it's predictive power. Specifically it predicts the pattern of chemically similar elements found in the periodic table.

Although the mathematical basis of quantum chemistry had been laid by Schrdinger, it is generally accepted that the first true calculation in quantum chemistry was that of the German scientists Walter Heitler and Fritz London on the hydrogen (H2) molecule in 1927. Heitler and London's method was extended by the American chemists John C. Slater and Linus Pauling to become the Valence-Bond (VB) [or Heitler-London-Slater-Pauling (HLSP)] method. In this method, attention is primarily devoted to the pairwise interactions of atoms, and this method therefore correlates closely with classical chemists' drawing of bonds between atoms.

An alternative approach was developed by Friedrich Hund and Robert S. Mulliken, in which the electrons are described by mathematical functions delocalized over an entire molecule. The Hund-Mulliken approach [or molecular orbital (MO) method] is less intuitive to chemists, but since it turns out to be more capable of predicting properties than the VB method, it is virtually the only computational method used in recent times.

A Quantum-Mechanical Theory of the Elementary Act of Chemical, Electrochemical and Biochemical Reactions in Polar Liquids was created in the 1970s by R.R. Dogonadze and others. R.R. Dogonadze was a founder of the well-known scientific school of quantum electrochemistry.

See also

bg:Квантова химия ca:Qumica quntica da:Kvantekemi de:Quantenchemie el:Κβαντική χημεία es:Qumica cuntica fr:Chimie quantique ja:量子化学 pl:Chemia kwantowa su:Kimia kuantum zh:量子化学


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