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Q & A: Why don't atoms explode - or collapse?

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Most recent answer: 05/13/2008
If like charges repel and opposites attract, then why do the protons in the nucleus of an atom hold together and why don't the electrons orbiting the nucleus crash into the protons causing nuclear fission and killing us all?
- Don Andrews (age 42)
Butler County Community College, Butler, PA USA

Don -

This is an excellent question, and the answer touches two very exciting fields: nuclear physics and atomic physics. The answer to your first question has to do with the strong nuclear force. This is probably a little less familiar to you than everyday forces like gravity and electro-magnetism, but it is extremely important. The strong nuclear force only acts between particles that are very very close together - i.e. only when they're as close together as the protons in a nucleus (about .000000000000001 meters). These forces are extremely strong - strong enough to overpower the repelling electric forces between the protons. For more on how nuclear forces work, look at our answer to the question .

As for the second part of your question, 'why don't the electrons fall into the nucleus,' have a look at our answer to the question .


(published on 10/22/2007)

Follow-Up #1: Electron capture in nuclei

so since an electron will not "fall" into the nucleus; Is it possible that if given enough energy to the atom, you could force an electron(s) into the nucleus possibly changing element? i.e. Forcing many extra electrons into the atom, extreme heat, superconductivity??
- Pippin Took (age 22)
Actually, in all atoms the surrounding electrons spend a small fraction of their time inside the nucleus.  Why they don't transmute one element to another by proton-electron capture is a matter of energetics.  In a few rare cases see this happens.  Forcing the electron into the nucleus, for example by shooting a high energy beam of electrons at a target, could induce transmutation but the probability is very small.


The energetic balance can be changed by extreme pressure, which favors electron+proton collapsing to neutron. This happens in neutron stars. Mike W.

(published on 05/13/2008)

Follow-up on this answer.