Tl3+ electron configuration

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Kristina Nguyen 1C
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Joined: Thu Jul 27, 2017 3:00 am

Tl3+ electron configuration

Postby Kristina Nguyen 1C » Fri Oct 27, 2017 5:15 pm

Why is the electron configuration for Tl3+ [Xe]4f14,5d10 and not [Xe]4f14,5d8,6s2?

Abigail Yap 2K
Posts: 51
Joined: Fri Sep 29, 2017 7:07 am

Re: Tl3+ electron configuration

Postby Abigail Yap 2K » Fri Oct 27, 2017 9:10 pm


I think this is because the three electrons removed from Tl to form Tl3+ are taken from the highest energy orbitals 6s and 6p. Therefore, the Tl configuration [Xe]4f14 5d10 6s2 6p1 will become [Xe]4f14 5d10.

Someone please correct me if I'm wrong!

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Re: Tl3+ electron configuration

Postby Chem_Mod » Fri Oct 27, 2017 9:33 pm

Hey Kristina!
So when the orbitals are empty 6s has a lower energy than 4f and 5d. But when these orbitals get filled with electrons, the 6s jumps in energy to be higher than the 4f and 5d energies. This happens at all s and d block intersections. For instance, we fill up the 4s orbital first before the 3d but once it is already filled we remove electrons from the 4s orbital first.

Also when removing electrons from a configuration, you remove them from the shell that is the farthest away from the nucleus. This means removing electrons right to left from your neutral atom configuration.

In order to get your correct neutral atom configuration, once you have the orbitals and the electrons in them, you must order them from lowest to highest energy.
For example, using the periodic table, you get Tl: [Xe]6s2 4f14 5d10 6p1

Ordering them lowest to highest energy gives you Tl: [Xe] 4f14 5d10 6s2 6p1

Then you remove 3 electrons to give you Tl+3: [Xe] 4f14 5d10.
Hope this helps!

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