What's the biggest molecule you can think of that forms a gas at standard temperature and pressure? Or, what's the densest possible gas at STP?

Radon? Idk, I forgot my chemistry a long time ago. But that would be my guess.

That's the heaviest pure element that's a gas, yeah, but I was wondering about compounds.

The densest gas is probably sulfur hexafluoride, and the molecule is pretty big too.

The densest gas is probably sulfur hexafluoride, and the molecule is pretty big too.

 

 

SF₆'s density is about 6.3 g/L (http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=34 gives its value at conditions slightly different than STP)

 

Radon's density is almost 10g/L