Therefore, there are no known stable compounds that contain helium.
However, there have been some theoretical predictions and observations of unstable helium compounds under extreme conditions:
* Helium hydride ion (HeH+) was detected in interstellar space. This is a very fragile molecule that is unstable at normal temperatures and pressures.
* Helium clusters are observed under extremely low temperatures and pressures. These are weak, temporary associations of helium atoms.
* Excitonic helium is a theoretical state where a helium atom is excited and can potentially bind with other atoms or molecules.
While these examples show that helium can interact with other elements under specific conditions, they are not considered true compounds in the traditional sense.
Overall, helium is generally considered a monatomic element that does not form stable compounds.
