The class of elements that includes all the elements that are gases at room temperature are the noble gases.

Here's why:

* Noble gases are found in Group 18 (VIIIa) of the periodic table.

* They have a full outer shell of electrons, making them very stable and unreactive.

* This stability prevents them from forming strong bonds with other atoms, which is why they exist as individual atoms in the gaseous state at room temperature.

The noble gases are:

* Helium (He)

* Neon (Ne)

* Argon (Ar)

* Krypton (Kr)

* Xenon (Xe)

* Radon (Rn)

While hydrogen (H) is also a gas at room temperature, it's not a noble gas. It belongs to Group 1 (Ia) of the periodic table and has only one electron in its outer shell, making it very reactive.