As others have alluded to, it's not the gas that matters as much as the dryness of it. If there's moisture in the air that's in your tyres, it will alter the pressure as temperatures increase, even well below boiling point.
I don't understand the science of it much, beyond knowing that the warmer air is, the more water vapour it will hold. I have seen it happen when I've finished a drink that comes in a lucozade sport type bag, closed it back up and left it in the car on a warm day. When I got back the bag had inflated itself!
As for sizes across the periodic table, look at the numbers. Less protons & neutrons = smaller. And helium diffuses through rubber at a daft rate, so I doubt we'll ever see it in bike tyres unless we start running mylar inner tubes.