# What is the Lewis Dot Structure for Mg_2^+?

Feb 4, 2017

If I were to take you literally, it would be a rather unstable cation...

${\left[\text{Mg"cdots"Mg}\right]}^{+}$
(the dots are an interaction line for a half-bond, not electrons)

Its MO diagram would have one less valence electron than that for ${\text{Mg}}_{2}$ (presumed in the gas phase!). This is the MO diagram for the NEUTRAL ${\text{Mg}}_{2}$ dimer:

Take one valence electron out of the antibonding ${\sigma}_{3 s}^{\text{*}}$, and we have a bond order that changed from $\frac{1}{2} \left(2 - 2\right) = 0$ to $\frac{1}{2} \left(2 - 1\right) = \frac{1}{2}$.

Thus, MO theory suggests that ${\text{Mg}}_{2}^{+}$ is more stable than ${\text{Mg}}_{2}$.

If you mean ${\text{Mg}}^{2 +}$, it has no valence electrons, so there is not much of a Lewis dot structure to draw... in fact, we have already "drawn" it by writing its chemical symbol and charge.