Final answer:
The valence electrons of neon are in the second energy level, with a full 2s and 2p orbital configuration, making it chemically inert according to the octet rule.
Step-by-step explanation:
The valence electrons of neon are located in the second energy level of the atom. Neon (Ne) has a total of 10 electrons, with the electron configuration being 1s²2s²2p⁶. Of these, the first two electrons fill the 1s orbital, and the remaining eight are the valence electrons that fill the 2s and 2p orbitals, making neon a noble gas with a fully filled valence shell. The stability of neon and other noble gases stems from this full valence shell, leading to their lack of chemical reactivity as they adhere to the octet rule. This rule indicates that atoms are most stable when they have eight valence electrons, akin to the noble gas configuration. In contrast, sodium (Na), which has one more electron than neon, places its eleventh electron in the 3s orbital. Upon losing this single valence electron, sodium adopts the stable electron configuration of neon, demonstrating the significance of a full valence shell for atomic stability.