Final answer:
The significance of 8 valence electrons is largely associated with atomic stability; atoms such as noble gases that possess a complete valence shell demonstrate minimal reactivity. Atoms will react with others to fill their valence electrons to achieve stability similar to that of noble gases.
Step-by-step explanation:
The importance of having 8 valence electrons is tied to an element's stability. Atoms strive to achieve a full outer energy level, as those with completely filled valence shells exhibit low reactivity, akin to the noble gases. Noble gases like helium (He), neon (Ne), and argon (Ar) have fully filled valence shells, with helium having two valence electrons, which is sufficient for the first energy level, while other noble gases have eight.
When atoms have fewer valence electrons, they are more inclined to participate in chemical bonding, either by gaining, losing, or sharing electrons, to achieve a full outer shell similar to noble gases. This is often referred to as seeking a 'noble gas configuration'. For instance, alkali metals in Group 1 of the periodic table, which have a single valence electron, are highly reactive as they tend to lose that one electron to reach the noble gas configuration. In contrast, noble gases do not typically form bonds due to their already stable configuration.
In response to the multiple-choice question, the correct option is (a): Stability; Noble gases. That’s because noble gases are known for being stable thanks to their filled valence shell, while other elements with fewer valence electrons, such as alkali metals or halogens, display higher reactivity due to their desire to complete their valence shell.