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Electron Configuration of Zinc (Zn)

Hello,

Could someone kindly explain why the correct electron configuration of Zinc is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰4s² rather than the expected 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰?
I'm aware that Zinc is a d-block transition metal which affects the electron configuration of the 4s and 3d orbital.

Any insight is much appreciated!


1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ (30 electrons)
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰4s² Given Zinc is a transition metal, the 4s orbital is filled after the 3d. (need to correct this explanation...)
[Ar] 3d¹⁰ 4s², [Ar] represents the electron configuration of Argon (1s² 2s² 2p⁶ 3s² 3p⁶)
(edited 2 months ago)
Reply 1
Original post by Chloe.B
Hello,
Could someone kindly explain why the correct electron configuration of Zinc is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰4s² rather than the expected 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰?
I'm aware that Zinc is a d-block transition metal which affects the electron configuration of the 4s and 3d orbital.
Any insight is much appreciated!

When writing out orbitals, you need to group all the orbitals in an energy level together, despite 4s filling up before 3d. Im pretty sure this is just to avoid things getting confusing with overlapping energy levels !! Hope this helps and sorry if this is a bad explanation
Reply 2
Thank you, I thin it's also to do with the fact that Zinc is a transition metal (in the d-block), but I'm not able to articulate it into words
(edited 2 months ago)
Original post by Chloe.B
Hello,

Could someone kindly explain why the correct electron configuration of Zinc is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰4s² rather than the expected 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰?
I'm aware that Zinc is a d-block transition metal which affects the electron configuration of the 4s and 3d orbital.

Any insight is much appreciated!


1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ (30 electrons)
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰4s² Given Zinc is a transition metal, the 4s orbital is filled after the 3d. (need to correct this explanation...)
[Ar] 3d¹⁰ 4s², [Ar] represents the electron configuration of Argon (1s² 2s² 2p⁶ 3s² 3p⁶)

You can write it either way, but I’d probably write it as (…) 3d^10 4s^2 because the 4s subshell is of higher energy than 3d for elements past scandium and so it is emptied first during ionisation (this is explained if you do undergraduate level chemistry - don’t worry about it if you are working at a pre-university level).

In case you are doing a pre-university level chemistry course such as A level, most will make it clear that zinc is not a transition metal as per the commonly taught definition “an element capable of forming a stable ion wherein the d-subshell is partially occupied”. It is, however, a d-block element.
(edited 2 months ago)
Reply 4
Thank you very much for the fantastic explanation, to confirm, does this mean that for Zinc, electrons fill the 3d orbital (lower energy level) before the final two electrons fill the 4s orbital?
Original post by Chloe.B
Thank you very much for the fantastic explanation, to confirm, does this mean that for Zinc, electrons fill the 3d orbital (lower energy level) before the final two electrons fill the 4s orbital?

I personally think that the 3d subshell would first as it is of lower energy and so the Aufbau principle would indicate this should be the case, but interestingly there are elements where 3d is lower in energy than 4s before Zn and yet 4s starts to fill out before 3d is filled out entirely (e.g Sc, Ti, V, Cr, Mn, Fe, Co and Ni). This is explainable in terms of various factors including the shielding and penetration effects, exchange energy and radial distribution functions, but of course these are undergraduate level topics.

In the case of zinc however, regardless of which order you decided to put the 3d and 4s electrons in, the arrangement would be the same and so it wouldn’t really matter.
(edited 2 months ago)

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