Question

How are Lewis dot diagrams used to represent ions?

Answer 1

Let's take a simple example. We start with the neutral species `H_3C-X`, and make the lithium reagent.

Explanation:

`H_3C-X + 2Li rarr H_3C-Li + LiX`

The methyl group in methyl lithium is formally anionic, which means that the `Li` nucleus has a formal positive charge. The methyl carbanion FORMALLY has 7 electrons associated with it; 2 of these are inner core; 3 of the valence electrons of C are involved in the `C-H` bonds (the other electron comes from the hydrogen!), and the remaining 2 valence electrons are assigned to the carbon. Since the carbon FORMALLY has 7 electrons, it has a formal negative charge, which balances the formal positive charge on lithium metal.