[Ne] 3s¹

Here's why:

* [Ne] represents the electron configuration of Neon, the nearest noble gas to Sodium. Neon has 10 electrons.

* 3s¹ indicates that Sodium has one additional electron in the 3s subshell.

Sodium has an atomic number of 11, meaning it has 11 electrons. The pseudo noble gas notation simplifies this by referencing the previous noble gas configuration, saving space and making it easier to understand the valence electron structure.