How are Lewis dot diagrams used to represent ions?

1 Answer
Feb 20, 2016

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


#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.