What characteristic of noble gases contributes to their stability?

The stability of noble gases is primarily due to their full outer electron configuration. Noble gases have eight electrons in their outer shell, which follows the octet rule that suggests atoms are most stable when they have a complete set of eight valence electrons. This full outer shell makes them less reactive compared to other elements, as they do not tend to gain, lose, or share electrons with other atoms.

In contrast to the other options, noble gases do not have high electronegativity, which is a measure of an atom's tendency to attract electrons in a bond. Their low molecular weight is not directly related to their stability, and while they can conduct electricity under certain conditions (such as when ionized), this ability does not contribute to their chemical stability in the same way their electron configuration does. Hence, the full outer electron configuration is the key aspect that makes noble gases stable and nonreactive.