Which statement is true regarding the stability of noble gases?

The statement about noble gases having full outer electron shells is true. Noble gases, such as helium, neon, argon, krypton, xenon, and radon, possess a complete valence shell, which includes eight electrons in their outermost shell (except for helium, which has two). This full outer shell configuration is responsible for their stability and is a key reason why noble gases are largely unreactive. Elements tend to be more stable when their outer shells are full, which is why noble gases do not readily participate in chemical reactions.

The other statements reflect common misconceptions about noble gases. The idea that noble gases readily form compounds with metals contradicts their reactivity characteristics, as they typically do not form compounds due to their stable electron configuration. The notion of noble gases having one valence electron is inaccurate, as they actually have a complete valence shell, and the suggestion that they have a tendency to gain electrons is also misleading, since their electron configuration already represents a stable arrangement, eliminating the need to gain electrons.