With the discovery of the negatively charged electron and the positively charged proton as the basic constituents of matter, physicists began to construct models of atoms. With experimental evidence indicating that neutral (uncharged) matter contains equal numbers of protons and electrons, it was clear that the simplest atom consists of one proton and one electron; constructing a model of this atom, hydrogen, was the first step in the development of a useful atomic theory. If the structure and dynamics of the hydrogen atom were understood, everything else would fall into place. At first sight, this task seemed fairly simple, because the electron and proton in the hydrogen atom pull on each other with a force that is similar in form to the gravitational pull between two bodies; the difference is that the gravitational pull depends on the masses of the interacting bodies (for example, the sun and a planet), whereas the electrostatic pull of the proton and electron on each other depends on the positive electric charge on the proton and the negative electric charge on the electron. The equal magnitudes of these opposite charges had been measured by Robert Millikan, so that the magnitude of the electrostatic pull of the proton on the electron for a given separation could be written at once, and all the mathematical techniques that had been developed since Newton’s time to handle the gravitational two-body problem (sun and planet) could be carried over to the atomic problem (proton and electron).
KeywordsStable Orbit Principal Quantum Number Lower Orbit Gravitational Pull High Orbit
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