# What is the closest an electron can get to a nucleus?

https://chemistry.stackexchange.com/questions/64270/coincidence-saying-that-an-electron-cannot-go-into-the-nucleus

This question got me thinking as to how close an electron can get to a nucleus. I thought that if it is possible to show that an electron can get closer to the nucleus than the value given in the question, then the answer would have no physical meaning.

• It's a meaningless question. The electrons (and nucleus, to a lesser extent) don't have a well-defined position, so they don't have a well-defined distance. – lemon Dec 11 '16 at 9:06
• Related: Why can't electrons be found inside the nucleus if there are infinite number of orbitals? Spoiler: they can! – John Rennie Dec 11 '16 at 16:51
• The PDF for electron density of a s-orbital is non-zero in the nucleus, which is to say that measurements of it's position will sometimes find it in the nucleus. For the 1s orbital the interior of the nucleus is more likely than any other comparable volume. – dmckee --- ex-moderator kitten Dec 11 '16 at 17:53

What is the closest an electron can get to a nucleus?

Electrons and nuclei are described in the quantum mechanical regime, so the correct question is "what is the probability of an electron to overlap with a nucleus".

For electrons in a bound state around a nucleus,S level (angular momentum zero) electrons have a probability of overlapping the nucleus position. Proof is that Kcapture can happen in nuclear physics, when the energetics allows it .

This question got me thinking as to how close an electron can get to a nucleus.

The probability exists, and is non zero for scattering electrons on nucleons, and is energy dependent . If you take the trouble to read this link you will get the idea.

I am not addressing the question you are referring to.

• Indeed, K-capture is a good argument. There are also the hyperfine effects that show overlap of the $s$-electrons with the nucleus: the Knight-shift in NMR, nuclear spin relaxation, Mössbauer shifts, hyperfine effects in optical spectra. – user137289 Dec 11 '16 at 10:41