Which of the following describes noble gases?

Noble gases are characterized by their complete valence shell, meaning they possess a full complement of electrons in their outermost energy level. This electronic configuration makes noble gases such as helium, neon, argon, krypton, xenon, and radon highly stable and largely unreactive under standard conditions. Their inertness is a key property that distinguishes them from other groups of elements, allowing them to not readily form compounds with other elements.

In contrast to other options, noble gases are not reactive and don't have incomplete valence shells, which is why the description emphasizing their inert nature and full valence shells accurately reflects their chemical behavior. Understanding this stability is critical in fields such as chemistry and physics because it explains why noble gases are often utilized in applications where non-reactivity is a desired trait, like in lighting and cryogenics.