måndag 7 oktober 2013

Quantum Contradictions 21: Atomic Radii?

Quantum Mechanics (QM) based on Schrödinger's equation is supposed to give a very accurate description of the atomic world, yet theoretical predictions of atomic radii presented in the literature based on solving Schrödinger's equation, agree with observations to only about 5%. This is excused by saying that the radius of an atom is not well defined, and so a precise number cannot be given.

In any case, QM is postulated to be very precise, and a precise answer will be delivered if only the question is the right one: Asking about the radius of an atom is not a good question and thus will have no good QM answer.

In contrast, the spin factor on an electron is claimed to be predicted by Quantum ElectroDynamics (QED) to one part in a trillion, which following Feynman is presented as ultimate evidence of the correctness of QED and thus also of its a little (less precise but still very precise) cousin QM.

So we have to live with the fact that asking for the radius of an atom will get no QM answer: The precision is about the precision that can be obtained from the above chart.

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