Eli5: Which is the most massive gas?

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What is the material with the most massive molecules that we are able to keep at the gas state? (Without chemical reactions happening and without non elastic shape deformations of the molecules). And why that one?

Edit: I mean, in a multi-molecule system, so that molecules have to withstand bumps.

In: Chemistry

4 Answers

Anonymous 0 Comments

My mind goes first to ultra-heavy nuclei in gaseous form. Something like uranium superheated. Each molecule has a mass equal to the atomic mass of the heavy material. If it needs to be radiologically stable, bismuth-209 is the heaviest this can get, with a molecular mass of 209. If you can have shorter half-lives, then whatever the heaviest element is in that half-life range.

Now, 209 is pretty thicc, but possibly not as huge as we can get. The first heavy ketone that came to my mind, dibutyl ketone, is already 142. I’m sure I could fuck around and find much heavier molecules that still worked, but for the sake of science, I’m going to take this a different direction. If we use the heaviest stable isotopes available for producing our dibutyl ketone, we can raise its molecular mass to 171. Getting closer.

More poking around, and I found dibenzyl ketone. It normally has a molecular mass of around 210, but with the heavier isotopes that could be increased to 241, proving that hydrocarbons win out over hot bismuth.

With even larger hydrocarbons, I’m sure you could get even more, but I’m going to leave it there.

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