Question

What gas moves the most ideally?
Ammonia
Carbon Dioxide
Oxygen

Answer 1

I think drawing out the structures will help us to figure it out. So ammonia has this pyramid sort of shape, that's not very ideal since it's not symmetrical really.
Carbon dioxide and oxygen are both straight lines, but carbon dioxide is longer and the two oxygen attached to the carbon can swing back and forth like this: while an oxygen molecule can't do that at all

An ideal gas would be one with no interactions at all with other molecules, but of course, no such gas exists. But it's a handy approximation!