We consider the quantum aspects of chemical and physical observations and operations, including quantum physics, quantum mechanics, quantum chemistry and the quantum laws of nature.
Abstract Of quantum physics, quantum chemistry, and quantum mechanics, the latter is least directly useful for both chemical education and the practice of chemistry as a science concerned with the reactions and properties of chemical substances. We show that quantum mechanics must be viewed as a collection of methods, numbering at least 13, that one might apply to make calculations on a system of an atomic scale. Instead of quantum mechanics, we advocate the quantum laws or laws of discreteness, which have simple roots in laws of conservation and which have practical applications in various areas of observations of chemical phenomena. We conclude that quantum mechanics is largely irrelevant for the general practice of chemistry.
This introductory chapter provides an overview of quantum mechanics, which is a subject of central importance in chemistry, and is by nature a mathematical theory. The chemist's approach to the understanding of matter and its chemical transformations is to take a microscopic view, connecting experimental observation with the properties of constituent molecules. However, at the microscopic level, atoms, molecules, and their constituent particles do not obey the familiar laws of mechanics that pertain to the everyday macroscopic world. For example, the existence of molecular line spectra indicates that molecules can be found only at certain well-defined energies, unlike objects at our own scale whose energy appears to be continuously variable. This book aims to explain the fundamentals of quantum mechanics from the point of view of chemistry; describe the areas of chemistry where quantum mechanics is most important; and show how quantum mechanics is applied to chemical problems.
When compared to classical mechanics (CM), quantum mechanics (QM) clearly appears as a difficult topic to the beginner. However, some knowledge of the basics of QM is a real need also for learners with predominant interest in experimental chemistry. Indeed, QM is the physical theory explaining most fundamental aspects of Chemistry, such as the periodic table of the elements and the chemical bond now called covalent, found by 19th century chemists and for a long time recognized as incompatible with the physical theories of the time (CM and classical electromagnetism). Going beyond the historical point of view, many peculiar aspects of QM and its very language permeate all modern chemistry so that a trustworthy understanding is required to deal with the matter in a sensible way.