Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 07/08/2015 04:50:01

Title: What's in the space between an atom's nucleus and its electron shells?
Post by: thedoc on 07/08/2015 04:50:01

Ethan asked the Naked Scientists:
   
I just wanted to know what the space between atoms and their electron shells. Is it made up of even smaller particles, or is it just completely empty? And if so, how is this possible?

What do you think?

Title: Re: What's in the space between an atom's nucleus and its electron shells?
Post by: evan_au on 07/08/2015 12:36:24

Quote from: Ethan

electron shells

In a sense, the electron shells fill the entire space around the atom.
An electron shell should not be considered as thin like an egg shell, but more like a fuzzy ball of fairy floss (https://en.wikipedia.org/wiki/Atomic_orbital).
All we can say is that there are some regions where the electron is likely to be found, and other regions where it is less likely to be found.

When you get very distant from a hydrogen atom, the chance of finding an electron there gets so small that you can effectively ignore it.

Quote

Is it made up of even smaller particles, or is it just completely empty?

The Casimir effect (https://en.wikipedia.org/wiki/Casimir_effect) is sometimes interpreted to mean that all of space is filled with fleeting virtual particles, which are flitting in and out of existence, all the time. According to this view, space is never entirely empty.

This is permitted by the Heisenberg uncertainty principle, which permits very short-lived variations in the energy of a system.

Title: Re: What's in the space between an atom's nucleus and its electron shells?
Post by: Bill S on 07/08/2015 13:30:06

I like the description. Evan. It seems that the closer one tries to look at QM the fuzzier things become.

It’s easy to think of an electron occupying a shell, or being somewhere within the “fairy floss”, and needing an input of energy to move outside that.  Then we are told that the electron could be anywhere in the Universe, without an apparent energy input. 
Is that something else we can blame Heisenberg for?   

Title: Re: What's in the space between an atom's nucleus and its electron shells?
Post by: yamo on 07/08/2015 13:35:32

So the chance of the electron at a given moment being say 12 billion ly away is non-zero?

Title: Re: What's in the space between an atom's nucleus and its electron shells?
Post by: chiralSPO on 07/08/2015 15:46:38

Quote from: yamo on 07/08/2015 13:35:32

So the chance of the electron at a given moment being say 12 billion ly away is non-zero?

It is effectively zero (even a few mm away from the nucleus, except inside some special materials, like metals). Our current theories predict non-zero probabilities of electrons from an atom at any point in the universe. However, if there is a 10^–10000 chance of an electron being found at a certain position, and there are only 10¹⁰⁰ electrons in the universe, then you would have to wait a very (VERY!) long time before such an event could be recorded. Therefore we typically assume it does not happen. But mathematically, it is often easiest to set up and evaluate a function without any boundaries, that just extends to infinity.

Title: Re: What's in the space between an atom's nucleus and its electron shells?
Post by: Colin2B on 08/08/2015 15:08:27

Quote from: chiralSPO on 07/08/2015 15:46:38

But mathematically, it is often easiest to set up and evaluate a function without any boundaries, that just extends to infinity.

This is similar to the calculation of the path of a photon between 2 points. Although all paths are considered, when the calculation is done for least time it is clear that the most probable path is a straight line.