Which one of the following is a correct electronic configuration of sodium?

Atomic number of sodium Z = 11.

The electronic configuration of sodium (Na) is

$\underset{\mathrm{K}}{1{\mathrm{S}}^2}2\underset{\mathrm{L}}{{\mathrm{S}}^{2}2{\mathrm{P}}^6} \underset{\mathrm{M}}{3{\mathrm{S}}^1}$

Therefore, the electronic arrangement in K, L and M shells is 2, 8, 1.