We will therefore present the theory in a semi-qualitative manner, emphasizing its results and their applications, rather than its derivation. In order to develop and present this theory in a comprehensive way, we would require a number of mathematical tools that lie beyond the scope of this course.

The modern theory of the atom makes full use of the wave-particle duality of matter. Our goal in this unit is to help you understand how the arrangement of the periodic table of the elements must follow as a necessary consequence of the fundamental laws of the quantum behavior of matter. Explain the relation between the absorption and emission spectrum of an atom.Describe the way in which Bohr's quantum numbers explain the observed spectrum of a typical atom.What is an atomic line emission spectrum? What is the significance of the continuum region of an emission spectrum? Sketch out a drawing showing the essentials of such a spectrum, including the ionization limit and the continuum.Sketch out a diagram showing how the concept of a standing wave applies to the description of the electron in a hydrogen atom.Give an example of a mechanical standing wave state the meaning and importance of its boundary conditions.State the major concepts that distinguished Bohr's model of the atom from the earlier planetary model.Describe the Thompson, Rutherford, and early planetary models of the atom, and explain why the latter is not consistent with classical physics.Make sure you thoroughly understand the following essential ideas:

Bohr's atom model