Then, physicists asked: how does the electron “know” where it is going? When it leaves one orbit, it gives off a photon of light.Once an electron was in orbit with an energy higher than the lowest possible energy, it would at some time move to a lower energy, but Bohr could not ascribe a cause to that event. Even worse, these “quantum jumps” in orbit seemed to occur without a cause.However, in the Bohr model nothing vibrated the light just appeared as the electron changed orbits. Scientists in 1913 expected that light was emitted in the same way, so an electron in an atom would vibrate to emit light. A radio station that broadcasts at 99.5 megahertz shakes electrons in its antenna 99,500,000 times per second. For radio, microwaves, etc., we still do that. The frequency of the shaking determined the frequency of the wave. In the early 20th century, electromagnetic radiation such as radio waves was created by shaking electrons back and forth.(I discussed this one in a previous post.) Bohr had no logical reason for the nonradiating electron, but without it, atoms would not exist. If it did, the electron would spiral quickly into the nucleus. Yet in Bohr’s model the orbiting electrons did not radiate. An electron moving in a circle is accelerating. An accelerating charged particle will emit continuous radiation.As a result of Bohr’s quantum-classical blended model, five major concerns arose. Thus, it was the beginning of a revolution but not as great as the revolution that was to come soon. Many physicists were not just unhappy with some of the assumptions, they were sure the entire model was absolutely wrong.īasically the Bohr model of the atom was an attempt to use the classical physics of Newton, Maxwell, and others but incorporate the quantum ideas of Planck and Einstein. However, like several other developments that I have discussed in these posts, the history is more complex. Physicists were troubled by some of its assumptions, but it worked, so they moved on. If you look at a description of the Bohr model of the atom in most textbooks or many popularized accounts, you could easily get the impression that it was an immediate success. In this installment of the history of atom theory, physics professor (and my dad) Dean Zollman discusses the problems physicists had with Bohr’s model – and they could get downright catty.
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