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### 2.43

Posted: Tue May 01, 2018 8:04 pm
Can some explain to me why silver is [Kr] 4d10 5s1 instead of [Kr] 4d9 5s2?

Thanks!

### Re: 2.43

Posted: Tue May 01, 2018 8:27 pm
I think silver is treated as a special case, just like Chromium. Filling the oribitals to d^5 and d^10 make elements more stable. In the case of chromium, when it looks like it should be [Ar]3d^4s^2, it becomes [Ar]3d^54s^1.

### Re: 2.43

Posted: Tue May 01, 2018 9:58 pm
I agree with what was stated above. I think it follows the exceptions discussed in class about how a full 3d orbital, d^10, has a lower energy than the 4s orbital and how the electrons occupy the lower energy state first before filling the 4s orbital in this case.

### Re: 2.43

Posted: Tue May 01, 2018 10:18 pm
This is because of stability. With 4d9 5s2, the d just needs one more electron in order to fill up the orbital. If it remains at 4d9 it is unstable, so it takes the electron from 5s2, the outer shell in order to fill its own. That causes it to become 4d10 5s1 instead.

### Re: 2.43

Posted: Thu May 03, 2018 12:33 pm
So how do we know when the element’s a “special case”? Do we only write, for example, 4d^10 5s^1 instead of 4d^9 5^2 when the element is near 4d^5 or 4d^10?

### Re: 2.43

Posted: Thu May 03, 2018 1:17 pm
Also, could someone please explain to me why for part e, tungsten is [Xe]4f^14 5d^4 6s^2? If you follow the logic stated in some of the previous replies of how 4d^5 and 4^10 are more stable than 4d^9, then shouldn’t the ground state electron configuration of tungsten be [Xe]4f^14 5d^5 6s^1 instead of [Xe]4f^14 5d^4 6s^2?

### Re: 2.43

Posted: Sat May 05, 2018 1:37 pm
Hi Joanna! I also had this same question about part e) and am not completely sure but this is what Chem_Mod said on another post regarding this:

“I believe that the reason that tungsten does not get a half filled shell is because it is in a lower row of the d-block. Additionally, it has the available f block electrons, which will stabilize the d block. Usually, the s orbital losing an electron to create a half filled or fully filled d configuration only occurs in the first two rows of the d block.”

### Re: 2.43

Posted: Sat May 05, 2018 5:12 pm
Joanna Pham 1A wrote:So how do we know when the element’s a “special case”? Do we only write, for example, 4d^10 5s^1 instead of 4d^9 5^2 when the element is near 4d^5 or 4d^10?

All the elements in the column Cr and Cu have this special case, but e- configuration should never be 3d^4 and 3d^9 because it should change to 3d^5 and 3d^10 to become stable.