Answer:
Helium is desired to hydrogen for filling balloons because it's miles non-flammable and more secure than hydrogen. Hydrogen fuel is especially flammable and might without difficulty ignite when uncovered to a spark or flame, which can purpose an explosion. In comparison, helium is an inert fuel that doesn't react with different elements or seize fireplace.
In addition to its safety advantages, helium is also more stable than hydrogen. Helium atoms are larger and heavier than hydrogen atoms, this means that that helium molecules circulate more slowly and are less probable to leak through the walls of a balloon. This makes helium a extra reliable fuel for filling balloons, as it may assist the balloon maintain its form and go with the flow for a longer period of time.