Electron Configuration of Scandium

[Jared Pagal 1J]

So in lecture on Wednesday, Prof. Lavelle used Scandium as an example to write out the electron configuration. His answer was Sc: [Ar]3d^1 4s^2. However, when I use the Aufbau principle, I get Sc: [Ar]4s^2 3d^1

Is the 3d orbital always going to be a higher energy level than 4s?

[Jessica Urzua-1H]

On the periodic table, the s-block comes before the d-block, so the d-orbitals appear to have higher energy than s-orbitals. However, when it comes to multi-electron atoms after the atomic number 20, the 4s state is higher than the 3d state. It is just an exception that is known for electron configurations. I hope this helps!!

[Victor Qiu 1C]

It should follow the order 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 5f 6d... However, I think [Ar] 3d¹4s² and [Ar] 4s²3d¹ are the same, and it does matter whether 4s or 3d is written first. They both represent the electron configuration of Sc.

[Kristina Krivenko 3I]

In one of the UA sessions, it was explained that, at first, 4s has lower energy, which is why it gets filled up first. However, once electrons occupy the 3d orbital, the energy "settles down," and 3d now has lower energy that 4s, so we write 3d and then 4s.

[Emma_Barrall_3J]

I think either is correct, but I would put 3d first.