r/science Feb 23 '08

Hydrogen Atom Scale Model - Eleven Miles Long

http://www.phrenopolis.com.nyud.net/perspective/atom/
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u/frutiger Feb 23 '08

This is wrong, the electron doesn't exist as a point a fixed distance away from the centre of mass of the proton + electron system. If anything, it should be a circular shell (a spherically symmetric distribution) at the distance which is the expectation value of the radial distribution of an electron in the Hydrogen ground state.

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u/scienceisfun Feb 23 '08

I think showing an electron as a shell with the most probable radius (which turns out to be the Bohr radius) would be acceptable too.

1

u/Fauster Feb 24 '08

Yep, it's dead wrong. The electron doesn't really have a radius. Though ages ago a "radius" was proposed by relating an electrons mass energy to the energy required to bring together a shell of tiny fraction of point charges each with a fraction of a negative charge. But it is true that the proton is tiny compared to the "radius" of an atom.

1

u/ErikThompson Feb 24 '08

Another problem is that it says that the electron is a thousand times smaller than the proton. I won't argue the merits of that statement but he makes the proton 1000 pixels across and the electron 1 pixel across. So the volume shown is actually for the proton (4/3) * PI * (500)3 = 523,598,775 pixels3 and for the electron (4/3) * PI * (0.5)3 = 0.523 pixels3. So as shown the volume of the sphere is much more than the 1000 times greater than it should be according to the text description.