Cr and Cu Exceptions

Moderators: Chem_Mod, Chem_Admin

Rebecca Epner 4A
Posts: 53
Joined: Sat Aug 17, 2019 12:18 am

Cr and Cu Exceptions

Postby Rebecca Epner 4A » Mon Oct 21, 2019 8:36 pm

And as a follow-up to my previous question, why are Cr and Cu exceptions to the 4s before 3d rule?

Thanks in advance

Posts: 102
Joined: Fri Aug 09, 2019 12:15 am

Re: Cr and Cu Exceptions

Postby KnarGeghamyan1B » Mon Oct 21, 2019 8:41 pm

The elements Cr and Cu are exceptions because their configuration, if you write it out, has 4 and 9 electrons in the 3d orbital. However, since these are one electron away from forming half shells (5 electrons in the 3d orbital) and full shells (10 electrons in the 3d orbital), an electron is pulled from the 4s orbital to fill the shells.

Posts: 87
Joined: Sat Aug 24, 2019 12:15 am

Re: Cr and Cu Exceptions

Postby Mashkinadze_1D » Mon Oct 21, 2019 10:33 pm

Basing off the previous reply, it would be very difficult to have a symmetric orientation when we are one away from having a much more stable (5 or 10) configuration for the d block. Therefore, because of the increased stability one electron will enter the d block from the s block to make it more stable. Without this stability, we would likely not see many of the aspects of these two elements that we do as they are vital to how they behave.

Return to “Electron Configurations for Multi-Electron Atoms”

Who is online

Users browsing this forum: No registered users and 2 guests