Final answer:
The configuration [Ne]3s¹ uses noble gas notation to simplify sodium's electron configuration, indicating its core electrons have the same configuration as neon's stable, filled outer shell, and one valence electron in the 3s orbital.
Step-by-step explanation:
The electron configuration [Ne]3s¹ is an example of using a noble gas inner core to represent the electron configuration of the sodium atom. The noble gas neon (Ne), with its electron configuration 1s²2s²2p⁶, represents the filled inner electron shells of sodium. Sodium, having an atomic number of 11, has the full electron configuration 1s²2s²2p⁶3s¹.
However, instead of writing out this long form, we can abbreviate it by using the preceding noble gas configuration of neon due to its stability and filled outer subshell, denoted as [Ne], and then appending the valence electron configuration, which in the case of sodium is 3s¹. This shorthand notation simplifies the representation of an atom's electron configuration and highlights the importance of noble gases like neon, which are characterized by high ionization energies and a reluctance to participate in chemical reactions unless under extreme conditions.