1). In the n-type layer, there is an excess of electrons, and in the p-type layer, there is an excess of positively charged holes (which are vacancies due to the lack of valence electrons). Near the ...

We find that it is the 4s orbital electrons that are ionised first before the 3d orbitals. We have to conclude that, ironically for the d-block elements, the 4s orbitals are in fact higher in energy ...