I am doing an assignment question where it is asking for the full electron configuration of Sb. I have already done the abbreviated electron configuration, which is [Kr] 4d10 5s2 5p3. I do not understand why this is, because according to my atomic orbital chart, I thought it should be [Kr] 5s2 4d10 5p3. Is Sb some kind of exception?
For the full electron configuration, I tried 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 4d10 5s2 5p3, and it was incorrect. Should 3d10 come before 4s2? What exception does Sb follow?