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What is the electron configuration of sodium?

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The electron configuration of sodium (atomic number 11) can be expressed in a few different ways based on the quantum-mechanical model and the shell atomic model:

Full notation: $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{1}$ 12
Shell distribution: 2-8-1 (representing the distribution of electrons across the K, L, and M shells)12
Shorthand notation: [Ne]3s¹, which uses the noble gas neon as a reference for the first 10 electrons1

This configuration indicates that sodium has a single valence electron in its outermost 3s orbital, which accounts for the high reactivity characteristic of alkali metals.1