Question

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

Answer 1

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:

`[Ne] 3s^1`

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

`[Ne]`

Or in longer-hand notation:

`color(blue)ul(1s^2 2s^2 2p^6)`

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

Therefore, all the electrons in `bb("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 `1s^2 2s^2 2p^6`. Hint: It's no more than `11`.)

I hope that helps!