When an electron from the n-type side fills a hole on the p-type side, it fills the valence shell. For reference, consider this video: https://youtu.be/7ukDKVHnac4?t=230. I learned in chemistry that atoms like this. So why do the electrons continue into neighboring holes if they are already part of a filled valence shell? I understand that part of it is from the electric potential of the battery attracting the electrons into neighboring holes. Is that it?