### orbitals

Posted:

**Sun Apr 29, 2018 10:32 pm**From the periodic table, can someone please explain why we can use [Ar] as Br and how do you do write it out, please and thanks

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=20&t=31211

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Posted: **Sun Apr 29, 2018 10:32 pm**

From the periodic table, can someone please explain why we can use [Ar] as Br and how do you do write it out, please and thanks

Posted: **Sun Apr 29, 2018 10:58 pm**

In class when the professor gave an example to find the orbitals for Bromine, he used shorthand and wrote [Ar] instead of repeating the same orbitals. I believe he said when we use shorthand to use the elements that are noble gases (group 18), but I am not sure exactly why that is the case.

When you write out the orbital, you know Ar has 18 electrons and you need 17 more electrons to make up the orbitals for Bromine. By looking at what comes after Argon and before/including Bromine, there are 2 elements in the s-block, 10 elements in the d-block, and 5 elements in the p-block all in the 4th row. So that means it's 4s^2, 3d^10, and 4p^5. But when you write it out the 3d^10 comes before the 4s^2 because the 4s state is higher in energy than 3d.

So the orbitals for Bromine would be:

[Ar] 3d^10 4s^2 4p^5

Hope this helped and is correct

When you write out the orbital, you know Ar has 18 electrons and you need 17 more electrons to make up the orbitals for Bromine. By looking at what comes after Argon and before/including Bromine, there are 2 elements in the s-block, 10 elements in the d-block, and 5 elements in the p-block all in the 4th row. So that means it's 4s^2, 3d^10, and 4p^5. But when you write it out the 3d^10 comes before the 4s^2 because the 4s state is higher in energy than 3d.

So the orbitals for Bromine would be:

[Ar] 3d^10 4s^2 4p^5

Hope this helped and is correct

Posted: **Sun Apr 29, 2018 11:27 pm**

To add on to that, you can use Ar because its outer shell, along with the outer shells of the other noble gases, is full, which makes it easier to have Ar as the reference point. Hopefully that helps!

Posted: **Mon Apr 30, 2018 5:22 pm**

Since Argon is a noble gas, the outer shell is filled and you can just start from the next row to get to bromine. So after you write Argon, you would start from the 4th row, but remember to use 3d before 4s. In this case, it would be 3d^10, 4s^2, and 4p^5 for bromine.