Hydrogen and helium are two elements that are kinda-sorta interchangeable in airships.
Hydrogen was once used to fill airships. Quite dangerous due to how flammable it is.
Hydrogen was the gas that was once used to filled airships. It is extremely plentiful and easy to produce. However, it is also extremely flammable and caused a few accidents. Helium is now used.
Helium is typically used to fill airships and balloons due to its low density, which allows them to float in the air.
The only answer that comes to mind is "Airships". Hydrogen, the lightest element, was used in airships, where excess weight was undesirable. However, accidents like the Hindenburg disaster showed that Hydrogen gas was too dangerous(it is extremely flammable) to be used. Since then, Helium has been used instead. Helium is also a very light element, and is completely safe, as it is inert.
An example of a gas element is helium, which is a noble gas commonly used in party balloons and airships.
Hydrogen (explosive), Helium (non-explosive).
Hydrogen used to be used in airships.
gas is still used in airships to provide lift.
That'd be hydrogen.
Airships are also, and more commonly, known as zeppelins. The term airship is also used to refer to an airplane, but this usage is incorrect, as they have two different meanings. Airships might also be called blimps or dirigibles.
Hydrogen
Helium has the chemical symbol He. It is a noble gas that is lighter than air and is commonly used in balloons and airships due to its low density.