Chapter 9 Quantum

Chapter 9 Quantum - Chapter 9 Quantum Theory Spring 2011...

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Unformatted text preview: Chapter 9 Quantum Theory Spring 2011 Fall 2009 Introduction and Background to Quantum Mechanics The use of theoretical principles to explain observable phenomena In the late seventeenth century, Isaac Newton discovered classical mechanics , the laws of motion of macroscopic objects. Newtons First Law of Motion : Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. This we recognize as essentially Galileos concept of inertia, and this is often termed simply the Law of Inertia. Newtons Second Law of Motion : The relationship between an objects mass, m , its acceleration a , and the applied force F is F = ma . Newtons Third Law of Motion : For every action there is an equal and opposite reaction. Foundations of Classical Physics: 1. Allows energy to have any desired value. 2. Predicts a precise trajectory for particles. In the early twentieth century, physicists found that classical mechanics does not correctly describe the behavior of very small particles such as the electrons and nuclei of atoms and molecules; the behavior of such particles is described by a set of laws called quantum mechanics . Quantum chemistry applies quantum mechanics to problems in chemistry . The influence of quantum chemistry is felt in all branches of chemistry. Physical chemists use quantum mechanics to calculate (with the aid of statistical mechanics) thermodynamic properties (for example, entropy, heat capacity) of gases; to interpret molecular spectra , thereby allowing experimental determination of molecular properties (for example, bond lengths and bond angles, dipole moments, barriers to internal rotation, energy differences between conformational isomers); to calculate molecular properties theoretically ; to calculate properties of transition states in chemical reactions, thereby allowing estimation of rate constants; to understand intermolecular forces; and to deal with bonding in solids . Organic chemists use quantum mechanics to estimate the relative stabilities of molecules, to calculate properties of reaction intermediates , to investigate the mechanisms of chemical reactions , to predict aromaticity of compounds , and to analyze NMR spectra . Analytical chemists use spectroscopic methods extensively. The frequencies and intensities of lines in a spectrum can be properly understood and interpreted only through use of quantum mechanics. Inorganic chemists use ligand field theory , an approximate quantum mechanical method, to predict and explain the properties of transition-metal complex ions . Although the large size of biologically important molecules makes quantum mechanical calculations on them extremely difficult, biochemists are beginning to benefit from quantum-mechanical studies of conformations of biological molecules , enzyme- substrate binding , and solvation of biological molecules . 9.1 Classical Mechanics Failed to Describe Experiments on Atomic and 9....
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This note was uploaded on 03/11/2011 for the course CHM 2211 taught by Professor Christenson during the Spring '11 term at FSU.

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Chapter 9 Quantum - Chapter 9 Quantum Theory Spring 2011...

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