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Name: Clayton
Status: educator
Grade: 9-12
Location: WI
Country: USA
Date: Winter 2011-2012


Question:
How does the size of electrons compare to the size of protons and neutrons?

Replies:
Clayton,

I wish I had a simple answer, but it depends on what you mean by 'size'. The easy answer is probably not what you are asking: these particles each have different masses -- electrons being much less massive than neutrons or protons. However, if you mean the spatial size ("length" or "volume"), the situation gets tricky.

It is common to think of atoms as little 'solar systems', and to think of electrons, neutrons, or protons like small hard spheres -- but in reality they are not like that at all. These particles behave very strangely -- to the point where a new branch of physics had to be created to describe them ("quantum physics"). It turns out, electrons are more like a 'smear' -- they act a little bit like particles, but also a little bit like waves. They are not all in one place at one time. The intuitive concept of "size" does not apply very well to these particles, and the question of spatial size turns out to be a tough one.

How do you describe the size of a wave? One answer is the wavelength, but just as with water waves, that answer for subatomic particles also "depends". The wavelength of an electron is a function of its energy and velocity -- so there is no single answer. Same story for other particles.

Hope this helps, Burr Zimmerman


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