Some important successes of classical quantum theory

Some important successes of classical quantum theory 

Historical discussions of the developments of quantum theory are dealt with adequately elsewhere, and so we focus only on some key points of classical quantum theory (in which the electron is considered to be a particle). 

At low temperatures, the radiation emitted by a hot body is mainly of low energy and occurs in the infrared, but as the temperature increases, the radiation becomes successively dull red, bright red and white. Attempts to account for this observation failed until, in 1901, Planck suggested that energy could be absorbed or emitted only in quanta of magnitude AE related to the frequency of the radiation, u, by equation 1.1. The proportionality constant is h, the Planck constant h = 6.626 x lO Is). 

Since the frequency of radiation is related to the wavelength, A, by equation 1.2, in which c is the speed of light in a vacuum (c = 2.998 x 10 m s ), we can rewrite equation 

1 in the form of equation 1.3 and relate the energy of radiation to its wavelength. 

On the basis of this relationship, Planck derived a relative intensity/wavelength/temperature relationship which was in good agreement with experimental data. This derivation is not straightforward and we shall not reproduce it here. 

When energy is provided (e.g. as heat or light) to an atom or other species, one or more electrons may be promoted from a ground state level to a higher energy state. This excited state is transient and the electron falls back to the ground state. This produces an emission spectrum. 

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Some important successes of classical quantum theory Bohr s theory of the atomic spectrum of hydrogen... 

There are several reasons for this unsatisfactory state of affairs. Most important is perhars the different conceptual demands on theories of chemistry and physics respectively. In this instance there has been no effort to re-interpret mathematical quantum theory to satisfy the needs of chemistry. The physical, or Copenhagen, interpretation, which is essentially an ensemble theory, is simply not able to handle the individual elementary units needed to formulate a successful theory of chemical cohesion and interaction. Computational dexterity without some mechanistic basis does not constitute a theory. Equally unfortunate has been the dogmatic insistence of theoretical chemists to drag their outdated phenomenological notions into the formulation of a hybrid theory, neither classical nor quantum even to the point of discarding... 

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