Aufbau Princple

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Leslie Romo 1C
Posts: 21
Joined: Fri Sep 25, 2015 3:00 am

Aufbau Princple

Postby Leslie Romo 1C » Sat Oct 17, 2015 12:15 am

Hi
Can anyone explain the "exceptions" to the Aufbau Principle?
I know that Silver is one of them but I don't understand why

Michelle Dela Rosa 1D
Posts: 25
Joined: Fri Sep 25, 2015 3:00 am

Re: Aufbau Princple

Postby Michelle Dela Rosa 1D » Sat Oct 17, 2015 12:43 pm

Silver is in the same group as Copper, which is an exception to the Aufbau Principle (the building-up principle), the other being Chromium. In these two cases, half full d^5 and full d^10 subshells have lower energy. For Chromium, the electron configuration would be [Ar] 3d^5 4s^1 instead of [Ar] 3d^4 4s^2; the half full d^5 subshell is lower in energy. Similarly, the electron configuration for Copper (Silver is in the same group) is [Ar] 3d^10 4s^1 instead of [Ar] 3d^9 4s^2; the full d^10 subshell is lower in energy. In these cases, lower total energy can be achieved if the electron enters a d orbital instead of the s orbital since the configurations complete a half subshell or full subshell.

MattDavid1d
Posts: 8
Joined: Thu Oct 01, 2015 3:00 am

Re: Aufbau Princple

Postby MattDavid1d » Sat Oct 17, 2015 10:08 pm

A half filled subshell in the d orbital is more stable than if there was a 6th electron. Additionally having a half filled d orbital provides more stability than a full s orbital and a d-orbital that is not full or half filled.


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