Building- Up Principle

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Adrienne_4F
Posts: 64
Joined: Fri Sep 28, 2018 12:27 am

Building- Up Principle

Postby Adrienne_4F » Mon Oct 22, 2018 7:00 pm

Why is copper [Ar] 3d^10 4s^1, not [Ar] 3d^9 4s^2? Same for chromium which is [Ar] 3d^5 4s^1, not [Ar] 3d^4 4s^2? I remember he mentioned it's so that the element is more stable. What does that mean?

Jayde Felix 4H
Posts: 59
Joined: Fri Sep 28, 2018 12:28 am

Re: Building- Up Principle

Postby Jayde Felix 4H » Mon Oct 22, 2018 7:07 pm

These were just the two exceptions that we need to know, and they are just understood.

rosemarywang4i
Posts: 34
Joined: Fri Sep 28, 2018 12:28 am

Re: Building- Up Principle

Postby rosemarywang4i » Mon Oct 22, 2018 8:08 pm

It's just been experimentally established that in those specific configurations, the atoms are at lower energy levels, so it's the default.

Emmaraf 1K
Posts: 94
Joined: Sat Oct 20, 2018 12:16 am

Re: Building- Up Principle

Postby Emmaraf 1K » Tue Oct 23, 2018 6:27 pm

It is believed that the half filled d subshell and half filled s subshell is a more stable configuration than when the s is completely filled but the d shell only has 4 electrons since having a half filled subshell increases stability.

cara_cavarretta_3F
Posts: 32
Joined: Fri Sep 28, 2018 12:23 am

Re: Building- Up Principle

Postby cara_cavarretta_3F » Tue Oct 23, 2018 6:58 pm

Do we need to know these exceptions for the test tomorrow?

A De Castro 14B 2H
Posts: 75
Joined: Fri Sep 28, 2018 12:29 am

Re: Building- Up Principle

Postby A De Castro 14B 2H » Tue Oct 23, 2018 7:01 pm

In addition to what everyone else has stated, the half filled d subshell in chromium and completely filled d subshell in copper are more stable configurations because they have comparatively lower energies than [Ar] 3d^5 4s^1 and [Ar] 3d^9 4s^2. I believe this is affected by Hund's rule as well; "each orbital of the subshells are occupied singly with electrons before double occupation occurs, in order to maximize the total spin quantum number for the electrons in the open subshells."


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