# What is the electron configuration of "Na"^(+)? How many paired electrons does it have?

Sep 2, 2017

Well, the typical ion that sodium (Na) forms, as an alkali metal (first column in the periodic table) is a $+ 1$ cation.

As a neutral atom, its electron configuration was:

$\left[N e\right] 3 {s}^{1}$

As a $+ 1$ ion, its electron configuration involves one less valence electron, giving it a noble gas core electronic structure:

$\left[N e\right]$

Or in longer-hand notation:

$\textcolor{b l u e}{\underline{1 {s}^{2} 2 {s}^{2} 2 {p}^{6}}}$

All "noble gas cores" have all electrons paired. We say that ${\text{Na}}^{+}$ is isoelectronic with (having the same electronic structure as) $\text{Ne}$.

Therefore, all the electrons in $\boldsymbol{{\text{Na}}^{+}}$ are paired.

(I'll leave it as an exercise for you to count how many electrons are paired from the electron configuration given by $1 {s}^{2} 2 {s}^{2} 2 {p}^{6}$. Hint: It's no more than $11$.)

I hope that helps!