Final answer:
Noble Gases have eight valence electrons, making them stable and inert, except for helium, which has two.
Step-by-step explanation:
The most stable elements, known as the Noble Gases, have a characteristic number of valence electrons that gives them unique stability. The number of valence electrons for most Noble Gases is eight, which fills their outermost electron shell, also known as the valence shell, fulfilling the octet rule. However, it is important to note that helium, which is also a Noble Gas, has only two valence electrons, but it still meets the rule for full energy levels for its shell. This full valence shell configuration makes the Noble Gases very inert and non-reactive compared to other elements that seek to achieve similar stable electron configurations by gaining, losing, or sharing electrons. Noble gases rarely form compounds because they have a full outer energy level, making them very stable and unreactive.