Recent comments in /f/space

Humble_Cook212 t1_jcxyve9 wrote

Reply to comment by lawblawg in How much space does it require to accommodate 1 hydrogen atom? by Alvsvar

That makes sense, thanks! I figured the mass/avogadro approach, while extremely useful for lots of stuff, proved not effective here at what I now read to be "what are the electron valence shell diameters". So it seems maybe I answered a question but the wrong question. :) Any thoughts on a different method that would get closer to the published 0.1nm?

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lawblawg t1_jcxxbd3 wrote

Reply to comment by Humble_Cook212 in How much space does it require to accommodate 1 hydrogen atom? by Alvsvar

You're right to do a sanity check; the size of a single atom of hydrogen is definitely not 3.7 cubic nanometers.

Your problem is that you used STP -- standard temperature and pressure -- above. At sea level pressures and temperatures, the gaseous hydrogen molecules (they're molecules, not individual atoms, but that's the least of our problems at this point) have so much kinetic energy that they are zipping around at hundreds of meters per second, constantly bouncing into one another. And so those constant collisions force them to spread out, until they occupy (on average) 3.7 cubic nanometers, even though they are physically infinitesimally smaller.

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