Order of subshells

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Jessica Beroukhim 3K
Posts: 21
Joined: Fri Sep 29, 2017 7:07 am

Order of subshells

Postby Jessica Beroukhim 3K » Thu Nov 02, 2017 2:17 pm

When is 4s higher energy than 3d and vice versa?
What does that mean for what order you write them in when writing e- configurations? What about for the order for the "exceptions" like Cu? And does that affect what order you take electrons out to make ions (like for Co2+ for instance)?

Mikaila 3E
Posts: 21
Joined: Fri Sep 29, 2017 7:07 am

Re: Order of subshells

Postby Mikaila 3E » Thu Nov 02, 2017 3:13 pm

4s has higher energy than 3d when there is an electron in the 3d subshell. The 4s is only lower in energy if there are no electrons in the 3d subshell hence why the 4s is filled before the 3d.

For example, potassium has an electron configuration of [Ar] 4s1. But if we go into the 3d subshell and look for scandium, the electron configuration is [Ar] 3d1 4s2.

This order still applies to copper (Cu) and chromium (Cr). The exceptions for copper and chromium is how many electrons are in each orbital in order to create a more stable state.

As ions, you still take away electrons from the higher energy level which is the 4s level leaving CO2+ as [Ar] 3s7.

Hope this helps!


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