Here's why:
* Nuclear Fusion: The nuclear reaction involving hydrogen atoms is called nuclear fusion. This process occurs under extreme conditions of temperature and pressure, like those found in stars.
* Hydrogen Isotopes: The most common form of hydrogen is called protium, containing one proton and one electron. However, there are two other isotopes: deuterium (one proton, one neutron, one electron) and tritium (one proton, two neutrons, one electron).
* Fusion of Hydrogen Isotopes: Nuclear fusion involves the merging of these hydrogen isotopes. The most common reaction is the fusion of deuterium and tritium, producing helium-4 (two protons, two neutrons, two electrons) and a neutron:
```
²H + ³H → ⁴He + ¹n
```
* Helium's Inertness: Helium is a noble gas, meaning it has a full outer shell of electrons. This makes it extremely unreactive and stable.
Therefore, helium is the unreactive gaseous product of nuclear reactions involving hydrogen atoms.
