Here's why:

* Noble gases are a group of elements in the periodic table known for their lack of reactivity. They have a full outer shell of electrons, making them very stable and unlikely to form chemical bonds.

* Radon (Rn) fits this description. It's a colorless, odorless, and tasteless gas that occurs naturally in the environment. It's radioactive, meaning its atoms decay over time, but that doesn't change its classification as a noble gas.