# $\mathrm{Na}^{+}$has completely filled $\mathrm{K}$ and $\mathrm{L}$ shells. Explain.

Question.
$\mathrm{Na}^{+}$has completely filled $\mathrm{K}$ and $\mathrm{L}$ shells. Explain.

Solution:
An atom of Na has a total of 11 electrons. Its electronic configuration is $2,8,1 .$ But, $\mathrm{Na}^{+}$ion has one electron less than Na atom i.e., it has 10 electrons. Therefore, 2 electrons go to $\mathrm{K}$-shell and 8 electrons go to $\mathrm{L}$-shell, thereby completely filling $\mathrm{K}$ and $\mathrm{L}$ shells.