Final answer:
Sodium has one valence electron in its 3s orbital. Its electron configuration is represented as 1s²2s²2p⁶6 3s¹, or in the noble gas shorthand as [Ne] 3s¹ after accounting for the core electrons.
Step-by-step explanation:
The number of valence electrons in sodium can be determined by examining its electron configuration. Sodium has an atomic number of 11, meaning it has 11 protons and, when neutral, 11 electrons as well. The electron configuration for sodium is 1s²2s²2p⁶6 3s¹, with the electrons in the highest energy level, the 3s orbital, being the valence electrons. Thus, sodium has one valence electron.
When sodium gives up its single valence electron to form a cation (Na+), it attains the electron configuration of neon, which is a stable noble gas with eight valence electrons. The core electron configuration for sodium can be represented using the noble gas shorthand as [Ne], which signifies the filled 1s, 2s, and 2p orbitals, reflecting the electron configuration of neon. Therefore, the condensed electron configuration for sodium is [Ne] 3s¹.