Even CO[sub]2[/sub] is a pretty heavy molecule, but it’s a gas at all terrestrial temperatures. But why on earth are SF[sub]6[/sub] and UH[sub]6[/sub] gasses? These are some darn heavy molecules!
Your enlightening facts will be most appreciated!
Sorry, I meant UF[sub]6[/sub].
Isn’t being a gas more to do with not having much in the way of inter-molecular forces?
Because they’re “happy molecules.” They have little in their structure which makes the interact with their fellow molecules. Without my copy of the CRC to hand, I would venture that these molecules have a little or no dipole moment and low polarizability, two properties which will tend to make molecules attracted to one another.
That’s correct, Shade. Even heavy molecules are going to be gaseous in a collection if they don’t ‘stick’ together. The gas will be dense & sink to the bottom of, say, an air-filled flask; but if the molecules are more or less free to move around relative to their neighbors-of-the-moment, the collection will be gaseous.