Light, modern theory

The modern theory of the electronic structure of the atom is based on experimental observations of the interaction of electricity with matter, studies of electron beams (cathode rays), studies of radioactivity, studies of the distribution of the energy emitted by hot solids, and studies of the wavelengths of light emitted by incandescent gases. A complete discussion of the experimental evidence for the modern theory of atomic structure is beyond the scope of this book. In this chapter only the results of the theoretical treatment will be described, These results will have to be memorized as rules of the game, but they will be used so extensively throughout the general chemistry course that the notation used will soon become familiar. 

Most modern theories are based on the equation of Ornstein and Zernike (OZ). This equation was developed eighty years ago to describe light scattering in a fluid. Its utility in the theory of fluids was realized much later, about thirty-five years ago. The OZ equation is obtained by defining the total correlation function,... 

Discussion of the H bond theory is divided into two portions in this chapter. First, the nature of the bond itself is considered, together with the relevant and informative data. Second, theoretical treatments of individual properties of H bonded systems (such as heat of formation, vibrational perturbations, NMR shifts, dielectric effects) are considered in the light of the first part. Before proceeding with the discussion, however, it will be helpful to review certain aspects of modern theory of the chemical bond. 

Modern theory is often called Bayesian probability theory after Thomas Bayes, F.R.S. (1702-1761) who was a minister of the Presbyterian church. The theorem attributed to his name is central to the modern interpretation, but according to Maistrov, it appears nowhere in his writings, and was first mentioned by Laplace though it was only expressed in words. The theorem enables an updating of a probability estimate, in the light of new information. For a set of mutually exclusive collectively exhaustive events Bi, B. ., B then P A) can be expressed. Fig. 5.4, as... 

And so it is that light from the supernova of modern times has come to reassure humankind of its ability to understand how the elements are synthesised in stars. At the same time, the fog of speculation has lifted from the theory of stellar evolution, culmination of astrophysical thinking, appointing it to the rank of a well-established science, based on a firm observational foundation. 

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