4f, 5d, and 6s orbitals

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Nawaphan Watanasirisuk 3B
Posts: 58
Joined: Tue Nov 28, 2017 3:03 am

4f, 5d, and 6s orbitals

Postby Nawaphan Watanasirisuk 3B » Mon Oct 29, 2018 1:02 am

I know 6s should be filled first before electrons can start filling 5d orbitals. The textbook states that after 6s is filled, 4f will start to be filled, and only after 4f is filled then electrons can start filling 5d? This is the case with the example of ytterbium [Xe]4f^14 6s^2. However, Cerium's electron configuration is as follows: [Xe]4f^1 5d^1 6s^2. Is Cerium an exception to the 4f first before 5d, and until what level would we need to be able to figure out the electron configurations (e.g. until 4f orbitals+)?

Fanny Lee 2K
Posts: 73
Joined: Fri Sep 28, 2018 12:29 am

Re: 4f, 5d, and 6s orbitals

Postby Fanny Lee 2K » Mon Oct 29, 2018 1:29 pm

I'm pretty sure all of Group 6 and Group 11 elements are also part of the exception. I'm curious about your second question too, if anyone would please explain?

EllerySchlingmann1E
Posts: 76
Joined: Fri Sep 28, 2018 12:24 am

Re: 4f, 5d, and 6s orbitals

Postby EllerySchlingmann1E » Mon Oct 29, 2018 2:17 pm

I'm pretty sure Dr. Lavelle said we only needed to know/be able to figure out electron configurations through the 4th period, so I would not worry about it. To answer your question about Cerium, there are a ton of exceptions to the rules that govern the first few periods in the later periods because the energy levels become so closely packed together and electrons shift very easily between those energy states. I'm sure for Cerium, the given electron configuration is the experimentally found configuration which is the lowest energy arrangement of electrons around the Cerium nucleus. Hope that helps!


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