Question

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

Answer 1

Na has a ground-state electronic configuration of $1s^{2}2s^{2}2p^{6}3s^1$.

Removing the 3s electron leaves us with the noble gas configuration $1s^{2}2s^{2}2p^6$ , so a sodium ion is Na+.

Electronic configuration of $Na$ is 2, 8, 1. One electron is removed for the formation of $N{a}^{+}$.

So the new electronic configuration is 2, 8.

Hence, 1st(K) and 2nd(L) shells are completely filled.