What gases diffuses most rapidly at stp?

diffusion is dependent on chemical reactivity (can't diffuse if you're in a bond)

and mass.

So the lightest most un-reactive gases will diffuse the quickest. Helium would seem to be the best contender. diffusion is dependent on chemical reactivity (can't diffuse if you're in a bond)

and mass.

So the lightest most un-reactive gases will diffuse the quickest. Helium would seem to be the best contender.