Above we see a classical electron moving around a nucleus, obeying the same laws that Kepler derived for planetary systems. This has become the most basic and intuitive model of the atom and yet it is wrong. In the real world the atom does not seem to naturally behave classically but that does not mean that we cannot make it do so!

If we wanted to make the ideal classical atom which still obeyed the laws of quantum mechanics, we would want the electron to have:

localization, though maybe not a point particle
and motion around an orbit.

The quantum mechanical realization of an ideal classical atom is depicted below:

Heisenberg's uncertainty principle provides us with a limitation on how well-localized we can make the electron's probability distribution but it does not prevent us from achieving significant localizion in three dimensions. There are ways to make such an electronic wave packet in a real atom but experimentally it is difficult. However, we can more easily make atoms which show just classical localization or just classical motion and although they are different from the ideal case, they still provide us with insight into to classical limit of quantum mechanics.

Previous Tutorial: Orbits in the Quantum World?

Tutorials

Next Tutorial: Making an Atom Behave Classically

Web page maintained by
Hideomi Nihira ( nihira@optics.rochester.edu ).
Last modified 13 September 2006