Page 97 - Bruno Linder Elementary Physical Chemistry

August 18, 2010 11:36 9in x 6in b985-ch08 Elementary Physical Chemistry

Chapter 8

Introduction to Quantum Theory

This chapter traces the historical development that led to the adoption of
quantum theory. In subsequent chapters, quantum theory will be applied to
atoms and molecules, to translational, rotational and vibrational motion,
and to spectroscopy.
Specifically, the present chapter deals with the following topics:
(1) Failure of classical mechanics
(2) Wave-particle duality
(3) The Schr¨odinger equation and the Born interpretation of wave-
functions
(4) The Uncertainty Principle and the Superposition of State
(5) Structure of atoms — atomic orbitals, energy levels, atomic spectra,
aufbau (build-up) principle, radius and ionization energy

8.1. Historical Development
Around 1900, science in general and physics in particular were considered
to be a self-contained, elegant disciplines. All known phenomena could
be explained, in principle, by what is now known as classical theory.
Specifically, the subjects that were well developed were

(1) Mechanics (dealing with motion)
(2) Light (electromagnetic radiation), electricity and magnetism
(3) Thermodynamics and statistical mechanics

However, when these classical theories were applied to systems of micro-
scopic dimension (atoms, molecules, etc.), they generally failed. To be

82