Can the following electron take up 'hole'? If so, this question is sort of leading onto a bigger question about PN junctions.
What is preventing the electron in the ion from moving to the next hole?
Is it to do with the strength of the covalent bond being stronger than that of the more positive charge in the hole?
Edit: What I'm trying to understand is why can't the extra electron in the negative boron ion, take up the holes to the left of it in the P (where I've drawn the red arrow in the 2nd diagram). Shouldn't that then allow another conducting electron to take up the hole in the positive ion? And can't this process keep happening till it's fully diffused? I'm still learning all this, this question is more out of curiosity.