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Q & A: Are atoms empty?

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Most recent answer: 05/31/2013
if objects are mostly empty space, due to the probability cloud taking up the majority of the "space" of the atom, why are objects solid at all?
- andrew (age 28)
lansdale pa
The electron wavefunction (the "probability cloud") fills the space of the atom. In fact, the region in which that wave is intense defines the extent of the atom. Remember, that wave is not some summary of the classical probability of finding some little particle dot somewhere. The wave is the physical state of the system. So far as we know, physical reality consists of nothing but such quantum waves. So if you want to say the region filled with wave is "empty" then absolutely everything is "empty".

So why do these waves make solid objects? The most important aspect of them is that you can't have waves representing two electrons in the same state. Electrons have  only two independent internal spin states, so this means you can't have more than two electrons occupying the same spatial wave state. So objects become hard to compress because when you try to squeeze more electrons into some space, they have to start occupying new, higher-energy states. They can't just all pile into the low-energy states.

Mike W.

(published on 01/17/2012)

Follow-Up #1: space inside atoms

Hello. My question is what makes up the space between the parts of the atom. I have always been toll since a young age that there is nothing there. I do not believe that is the true answer. Something has to be there. Is there any forces or maybe something holding the electrons back from going to the protons because I assume they are attracted?
- Ronnie Jebara (age 15)
Chester, New Jersey, USA

Hi Ronnie- That's a nice question. We think that you can put together a good answer from ones we've already posted. (; ; ...)

Mike W.

(published on 05/31/2013)

Follow-up on this answer.