Electron Configuration for Bi3+

[Mike Matthews 1D]

Hi, I'm wondering how one would go about writing the electron configuration for Bi+3. Since Xenon is the previous noble gas, I started by writing [Xe]. Then since Bi is in the 6th period I continued adding electrons with n=6 until I reached 80 electrons. I got the configuration [Bi]6s2 6p6 6d10 6f8. However, the correct answer is [Xe] 4f14 5d10 6s2. Could someone please explain this to me.

[Lucian1F]

For the d sublevel, you need to subtract one from the principle quantum number, so it would be 5d. For the f sublevel, you need to subtract two form the principle quantum number, so it would be 4f.

[Victor Qiu 1C]

Because it should follow the order 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 5f 6d...