"The physicists have known sin; and this is a
knowledge which they cannot lose"
J. Robert Oppenheimer
- In order to provide a full theoretical description of the
Hydrogen atom (or any other atom) we must use Quantum Mechanics.
However, before quantum mechanics was fully developed the Danish
Niels Bohr proposed a model of the Hydrogen atom which relied
primarily on classical ideas. This "Bohr
model" was successful in describing some of the basic properties of
the Hydrogen atom.
Bohr model assumes that the Hydrogen atom electron moves in cirular
orbits about the proton, but that only orbits of particular
radii, rn are allowed where,
r1 is the radius of the smallest allowed orbit and n can
take on integer values and is called the principal quantum number
. The value of r1 is 5.3 x 10-11 m (called
the Bohr radius) and provides a measure of the size of the Hydrogen
- The fact that only orbits of particular radii are allowed seems
strange when compared to a "planetary" system; there is nothing
about the distance at which the earth orbits the sun, it could easily
somewhat smaller or larger. But we have already seen one
where an apparently continuous variable is constrained to have only
values. The standing wave patterns
on a stretched string allow only certain frequencies of vibration.
- The deBroglie wavelength of the Hydrogen electron in the smallest
radius orbit is equal to the circumference of that orbit (both about
3.3 x 10 -10 m). The electron can be thought of as
behaving in a similar manner to the stretched string which exhibits a
standing wave pattern.
Only orbits with a circumference equal to an integer multiple of
electron wavelengths will be allowed.
did the chicken cross the road ?
Einstein: "Whether the
chicken crossed the road or the road
moved beneath the chicken depends on your frame of reference."
Dr. C. L. Davis
University of Louisville