# Distances between Atoms in a Gas Molecule

1. Jul 31, 2006

### dingsbunnyranch

How do you calculate the distances between atoms of a given gas molecule? The reason im asking this is so I can find the moment of inertia of certain molecules so i can determine degrees of freedom for a gas at a certain temperature. Is there an easier way to determine them?

2. Jul 31, 2006

### Pythagorean

can't gas expand and compress? Wouldn't this imply that there is no absolute distance between atoms in a gas, and that its relative to the pressure and volume?

Just using logic, with no advanced physics training (i'm just starting my third year as a physics undergrad), I'd guess that you could use the ideal gas law:

PV = nRT where P is Pressure, V is volume, n is number of moles, R is the gas constant, and T is the temperature.

you could find out the volume per atom (V/n = RT/P) and derive it from there, i suppose. But I think gases rely on fluid dynamics, which are really complex, and the distance between atoms will be different for different localities within a given 'cloud' of gas.

3. Aug 1, 2006

### HallsofIvy

Staff Emeritus
Pythagorean, I think you misunderstood the question. The question was not about the distance between molecules (atoms) in a gas but about the distance between atoms in a single molecule.

I don't see any simple way to answer that- it depends on the type of gas. You might be able to look up distance between atoms for a particular molecule in something like the CRC tables.

4. Aug 1, 2006

### Pythagorean

ah, yes, I see. I think this is a common study in chemistry.

from wikipedia:

http://en.wikipedia.org/wiki/Chemical_bond/Temp [Broken]

Last edited by a moderator: May 2, 2017
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