Cu and Cr electron configuration exceptions

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Hadji Yono-Cruz 2L
Posts: 64
Joined: Fri Sep 28, 2018 12:26 am

Cu and Cr electron configuration exceptions

Postby Hadji Yono-Cruz 2L » Sat Nov 03, 2018 1:35 am

Why do Cu and Cr not follow the same trend of writing the electron configuration as other atoms?

Dayna Pham 1I
Posts: 98
Joined: Fri Sep 28, 2018 12:16 am
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Re: Cu and Cr electron configuration exceptions

Postby Dayna Pham 1I » Sat Nov 03, 2018 1:47 am

Copper and Chromium are exceptions to the common electron configuration methods because they are one electron away from reaching a more stable state (a half-filled 3d subshell for Chromium with 5 electrons under Hund's Rule, and a filled 3d subshell with 10 electrons under the Pauli Exclusion Principle).

Chromium is, according to the periodic table, [Ar]3d4 4s2, but it wants to become more stable with a half-filled 3d subshell, so one electron from 4s moves to 3d, making it [Ar]3d5 4s1.

Copper is, according to the periodic table, [Ar]3d9 4s2, but it wants to become more stable with a completely filled 3d subshell, so one electron from 4s moves to 3d, making it [Ar]3d10 4s1.

The most stable state for subshells is completely filled, and the second most stable state for subshells is half filled.

Hope this helped!


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