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Q & A: Electron repulsion

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Most recent answer: 08/23/2011
Q:
Why can't we pile up bunch of electrons (say 10) around a single proton--i.e., around hydrogen atom? I know that the number of electrons is limited by the shell number i.e., 2n^2 where n is the shell number. Is the number of electrons limited by the number of protons? What is the formula? It seems to me that a single proton should be able to keep a number of electrons in orbit just as a single planet that can keep several same-sized planets as long as they are symmetrically centered on one planet.
- Mehran (age 60)
Miami, FL
A:
Hi Mehran- the answer to this one is pretty simple. After the first electron is bound, the atom is neutral. So there's no net attraction of the next electron when it's at a big distance. Since the electron wave functions can adjust to each other to minimize energy, one more electron can still bind with net negative energy. (see ) However, now you have a negatively charged object which strongly repels any additional electrons. At this point, a classical guess that no more could bind would be correct.

Gravity is very different, because all the forces are attractive.

Mike W.

(published on 08/23/2011)

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