http://www.ck12.org Chapter 5. Electrons in Atoms
FIGURE 5.7
Bohr’s atomic model.Wave-Particle Duality
French born Physicist Lois de Broglie (1892–1987) studied diffraction patterns of electrons, which seemed to
indicate that electrons were behaving as waves, even though they were composed of matter. Further diffraction and
interference experiments confirmed these findings. In 1924, de Broglie showed that particles exhibit wavelengths that
are inversely proportional to their momentum. Because of this inverse relationship, large objects have wavelengths
that are immeasurably small, so wave behavior is not observed. However, the momentum of a very tiny particle, like
an electron, can be small enough to detect wave-like behavior during certain types of experiments.
Electrons as Particles
Two years after de Broglie’s work, in 1926, the Austrian physicist Erwin Schrödinger (1887–1961) found that the
behavior of electrons in atoms could be described by considering them to be standing waves. He was able to
incorporate both particle behavior (mass) and wave behavior (an indefinite location in space) into one equation. The
mathematical wave function for an electron provided a way to predict the probability of finding the electron in a
given region of space. Schrödinger received the Nobel Prize in physics in 1933.
Heisenberg Uncertainty Principle
At about the same time that Schr ̈dinger was working out the mathematics of standing waves, the German physicist
Werner Heisenberg (1901–1976) showed mathematically that it is impossible to determine simultaneously the exact
location and the exact velocity of an electron, or of any other particle. In 1927, Heisenberg presented a paper in
which he showed that “the more precisely the position of a particle is determined, the less precisely the momentum
is known in this instant, and vice versa” (Hilgevoord and Uffink 2011). This later became known asHeisenberg’s
uncertainty principle.