What is a key reason for neon’s unreactivity?

Neon’s unreactivity can primarily be attributed to its electron configuration, specifically that it has 8 electrons in its outer shell. This outer shell configuration is known as being "noble" or "stable," as it fulfills the octet rule, which states that atoms are most stable when they have eight electrons in their valence shell. As a result, neon does not tend to gain, lose, or share electrons with other atoms, leading to its characteristic inertness.

While other elements might react to achieve a full outer shell, neon already possesses the optimum configuration for stability, making it unreactive under standard conditions. Thus, this stable electron arrangement is the fundamental reason neon remains largely non-reactive compared to elements that do not have a full outer shell.