Chemical bonding principles

As an introduction to the more complicated surface chemical bonding, we first present the chemical bonding principles in simple molecular systems. These same concepts are subsequently used to begin to analyze to the adsorbate-surface bonds. 

The flash lamp teclmology first used to photolyse samples has since been superseded by successive generations of increasingly faster pulsed laser teclmologies, leading to a time resolution for optical perturbation metliods tliat now extends to femtoseconds. This time scale approaches tlie ultimate limit on time resolution (At) available to flash photolysis studies, tlie limit imposed by chemical bond energies (AA) tlirough tlie uncertainty principle, AAAt > 2/j. 

The progression of sections leads the reader from the principles of quantum mechanics and several model problems which illustrate these principles and relate to chemical phenomena, through atomic and molecular orbitals, N-electron configurations, states, and term symbols, vibrational and rotational energy levels, photon-induced transitions among various levels, and eventually to computational techniques for treating chemical bonding and reactivity. 

The principles of infrared spectroscopy can be exploited to extract information on the chemical bonding of an extremely wide variety of materials. The greatest strength of the technique is as a nondestructive, bulk probe of glassy and amor-... 

ISS involves simple principles of classical physics and is one of the simplest spectroscopy for quantitative calculations. Under most standard instrumental operating conditions there is essentially no dependency on the chemical bonding or matrix of the sample. Several workers have discussed quantitative aspects of ISS and ele-ihental relative sensitivities. These have been compiled with comparative measurements of sensitivity obtained from several different laboratories and are shown in... 

MO (molecular orbital) theory (Appendix 5). Our experience has been (and continues to be) that although this approach is important to chemical bonding, most general chemistry students do not understand it but only memorize the principles discussed in the classroom. 

We see again that there is but one principle which causes a chemical bond between two atoms all chemical bonds form because electrons are placed simultaneously near two positive nuclei. The term covalent bond indicates that the most stable distribution of the electrons (as far as energy is concerned) is symmetrical between the two atoms. When the bonding electrons are somewhat closer to one of the atoms than the other, the bond is said to have ionic character. The term ionic bond indicates the electrons are displaced so much toward one atom that it is a good approximation to represent the bonded... 

The initial set of experiments and the first few textbook chapters lay down a foundation for the course. The elements of scientific activity are immediately displayed, including the role of uncertainty. The atomic theory, the nature of matter in its various phases, and the mole concept are developed. Then an extended section of the course is devoted to the extraction of important chemical principles from relevant laboratory experience. The principles considered include energy, rate and equilibrium characteristics of chemical reactions, chemical periodicity, and chemical bonding in gases, liquids, and solids. The course concludes with several chapters of descriptive chemistry in which the applicability and worth of the chemical principles developed earlier are seen again and again. 

After the discovery of quantum mechanics in 1925 it became evident that the quantum mechanical equations constitute a reliable basis for the theory of molecular structure. It also soon became evident that these equations, such as the Schrodinger wave equation, cannot be solved rigorously for any but the simplest molecules. The development of the theory of molecular structure and the nature of the chemical bond during the past twenty-five years has been in considerable part empirical — based upon the facts of chemistry — but with the interpretation of these facts greatly influenced by quantum mechanical principles and concepts. 

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