Copper

[Krista Mercado 1B]

Why is the ground state electron configuration of copper [Ar]3d^(10)4s^(1) and not [Ar]3d^(9)4s^(2)?

[Mahir_Hasan2C]

It is more stable to be in 3d10 in comparison to 3d9 as it is closer to the full shell.

[Peter Nguyen 2I]

I believe it is that way because 3d9 has an unpaired electron which makes it unstable and 3d would rather have a full shell to stabilize it.

[cara_cavarretta_3F]

It helps me to think about it being more beneficial to have a full shell of 10 electrons rather than a full shell of 2 electrons. Remember this is also the case for Cr, in which a half shell of 3d5 with all electrons of the same spin is more stable than having a full 4s2 and 3d4.

[Kunseo Yook 2E]

Is this the same for every element below copper and chromium? And are there any other elements with this kind of exception?

[EllaBerry]

It is more stable when the 3d orbital is full, which it is when it is at 3d10.

[sonalivij]

Is this the same for every element below copper and chromium? And are there any other elements with this kind of exception?

As you go down the periods, the elements are farther away from the nucleus and stop adopting this rule

[Briana Perez 3A]

It is an exception to the period table and just has to be memorized. Because the 3d orbital is so much larger than the 4s, it pulls one electron to fill its empty space and is therefore full. Essentially, it is more stable in this configuration.

[Michael Nirula]

^Yeah, Cu and Cr are exceptions

[Ian Marquez 2K]

Also, it has been experimentally observed that half-filled subshells are more stable than predicted. The electron configuration exception of copper allows it to have half-filled subshells making it its most stable ground state and proper electron configuration.

[shaunajava2e]

^^ the rule applies for copper and chromium and all elements under them in the 9th and 6th groups (however lavelle said in class we won't be going past the 4th period so we don't need to worry about any elements other than copper and chromium)