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What force (or theory) keeps the electrons in the 1s orbital from hitting the nucleus or eventually running out of energy? Also how does that relate or does it ever relate to the decay of an atom?

The question you ask was actually exactly (or pretty close to) the question that prompted the development of quantum mechanics. The weird thing about quantum states is that they are quantized -they are simply not able to go continuously from one energy state to another - so in particular the 1s electrons are stuck in the lowest possible energy state - there just is nothing lower in energy - they have already run out of all they are allowed to. They actually do "hit the nucleus" in a sense, but the nucleus itself is also almost always in its lowest energy state, and so it and the electron just very agreeably coexist. The one exception to this is in a strong magnetic field, where the nucleus can have a bunch of different energy states depending on the magnetization. This does not effect the inner electrons at all, but the outer electrons can see this effect, and you get all sorts of wonderful stuff from which we can now do "NMR" or "MRI" imaging. I am not sure what you mean by the decay of an atom - most atoms do not decay, unless they start out in some unstable high-energy state (for example the nucleus could be radioactive and decay into something different).

Arthur Smith

Well, you could have K-shell capture... that is not a decay in itself, but the excited nucleus formed can decay into other nuclei, or (more likely) kick off a gamma particle (photon).


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