Electron transfer

[Chloe Borja 2D]

Hi! I understand that the Lewis definition of acids and bases is centered around electrons, but I can't really comprehend the transfer of electrons.

For example, when ammonia (NH3) is surrounded by water molecules, ammonia acts as the Lewis base because it donates electrons. But where are those donated electrons going to? Are they going to the proton or the residual hydroxide (OH-) molecule? It just doesn't really make sense to me because I imagine that the lone pair on N in NH3 is "given" to the incoming H+, but it's still paired with N because it enables an N-H bond (so is it really being donated?).

If someone could explain this, that would be great!

[Paul Zhang 2F]

Hello! In aqueous solution, the equilibrium reaction for ammonia is NH3(aq) + H2O(l) <--> NH4+(aq) + OH-(aq). The donated lone pair goes to water, helps kick off an H+ (proton), and forms hydroxide. The kicked-off H+ bonds with the ammonia to form the ammonium ion.

NH3 has 8 valence electrons, H2O has 8 valence electrons. As expected (since a lone pair is donated by NH3), NH4+ has 7 valence electrons while OH- has 9 valence electrons.