= Electron configuration
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An <electron configuration> records the occupation of <electron shells> and <electron subshells> by <Electrons>. For neutral <sodium> in its <ground state>, $1s^2\,2s^2\,2p^6\,3s^1$ gives $2+2+6+1=11$ <Electrons>; adding the occupations within each <electron shell> gives $(2,8,1)$. A superscript counts <Electrons>, rather than multiplying the preceding labels. Removing the outer <Electron> gives the <sodium> <ion> $\mathrm{Na}^{+}$ with $1s^2\,2s^2\,2p^6$, or $(2,8)$. See https://openstax.org/books/chemistry-2e/pages/6-4-electronic-structure-of-atoms-electron-configurations[Flowers et al., Chemistry 2e, electron configurations of atoms and ions].
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