why my answer is wrong? --- remove electron from orbital question: In forming Ni+ and Ni2+, the nickel atom loses electrons from which orbital(s)? I looked at the periodic tale, and Ni is in the middle, where the 3d orbital located. so when you need to remove one or two electrons, you should remove from the 3d orbital. but that is not right? the answer for that is 4s instead of 3d orbital. i don't get it. the 3d should have higher energy than 4s, so how can you remove the 4s, but not 3d first?