Was quantum shell theory disproved?
July 27, 2007 6:25AM
Quantum shell theory was first proposed by the physicist Niels Bohr as an explanation of the unexpected complexity of the spectra of hydrogen and various other atoms. According to Bohr each quantum shell represents a certain state of energy, attributed to the electron orbiting within that shell. So an electron within the lowest shell would be orbiting at the orbit closest to the nucleus, and thus has the least energy, whereas an electron within a higher shell would be orbiting at the next closest orbit to the nucleus, and thus has a bit more energy by a discrete amount as given by Planck. However, it was noted that this explanation, although it worked perfectly with hydrogen, became more and more inaccurate as the atomic mass of the element in question increased. Therefore, later the electrons and nucleic particles in Bohr's quantum shell theory, with its discrete, pointlike particles, was augmented by another description from wave mechanics, based on Schrodinger's equation, that envisioned Bohr's discrete particles as a sort of vibrating instrument- although what exactly it is that vibrates, and what exact relation it bears to the particle, did not seem to be clear at the time (and is still ambiguous to some extent now). After the assertions of wave mechanics were successfully tested (such as the predicted diffraction of electrons etc.), its description was recognized for the wonder it was, and nowadays replace quantum shell theory as a more accurate and complete description for the working of the atom. This is not to say, however, that quantum shell theory was disproved, just as the dawn of relativity does not disprove Newtonian mechanics. All the modern quantum mechanics, with its powerful wave equation, has done was to replace Bohr's more naive view with a more mature, complete and accurate understanding of the working of the atom. The fact that Bohr was superseded does not mean he was wrong, merely that his description was not complete or nearly accurate enough to account for the phenomena observed. Even now, because of the simpler maths, it's still used as a introduction to the weird wonders of the quantum world.