Helium vs hydrogen (Balloons)?

Question

OK, if we fill a balloon with helium we know after about 48 hrs its buoyancy will degrade... (what is happening to the helium?)

but if we fill a balloon with hydrogen its suppose to be even more buoyant , my question is will its buoyancy degrade at the same rate/faster/slower? and why?

Answer 1

Helium is a "sneaky" gas, its atoms are quite small (smallest calculated atomic radius of any element, 31 pm, as compared to 53 pm for the hydrogen atom), and since it is mono-atomic, its molecule are the same as atoms. It will find every little way of escaping, it can diffuse (slowly, but still...) through nearly all material. In the case of a balloon, the layer is understandably thin in order to keep it light, and it inevitably leaks.

Hydrogen is about 8% more buoyant than helium, but its molecules are larger so it will not leak (although hydrogen embrittlement, the interaction of hydrogen diffusing into metal making it fragile, is a known phenomenon) as much as helium.

Answer 2

Helium is atomically 4 times as big as hydrogen.

The balloon is just a very tight membrane.

It will leak.

The hydrogen will leak faster.