## Electron Configuration for Fe 3+

Daniel-1G
Posts: 14
Joined: Wed Sep 21, 2016 2:59 pm

### Electron Configuration for Fe 3+

Could someone explain to me why the electron configuration for Fe 3+ is not the same as Vanadium of [Ar]3d3 4s2 and is instead [Ar]3d5? Is this just an exception like copper that we should have memorized?

Armo_Derbarsegian_3K
Posts: 35
Joined: Sat Jul 09, 2016 3:00 am

### Re: Electron Configuration for Fe 3+

Fe is [Ar]3d6 4s2
Fe2+ loses the 4s2
Fe3+ loses an electron from the d
so Fe3+ is [Ar]3d5

Not really an exception, just remember a full d/half full d will be much more stable(chromium/copper)

Alyssa_Wieand_2G
Posts: 19
Joined: Wed Sep 21, 2016 2:58 pm

### Re: Electron Configuration for Fe 3+

When I work this out, I first write out the structure for the ground state configuration which would be [Ar] 3d^6 4s^2 and then I just take electrons out in the order that is written so Fe3+ would be [Ar]3d^5 since the 4s block has slightly lower energy and they are filled first. Hope this helps!

Rachel Wile 2D
Posts: 49
Joined: Sat Jul 09, 2016 3:00 am

### Re: Electron Configuration for Fe 3+

You take electrons out of the 4s orbital, before you take them out of the 3d orbital, because it is lower energy to have them in the 3d orbital in comparison to the 4s.

Posts: 17
Joined: Wed Sep 21, 2016 2:58 pm

### Re: Electron Configuration for Fe 3+

How can you tell if the orbital has a lower energy level? Is it just something we have to memorize. I've heard Dr. Lavelle say this many times in lecture so is it just like something that's given?

Helen_Onuffer_1A
Posts: 15
Joined: Fri Jul 22, 2016 3:00 am

### Re: Electron Configuration for Fe 3+

I think that once you start filling the 3d orbital, it becomes lower energy than the 4s orbital. It's probably more complicated than that, but we haven't really learned all the details yet.