Orbitals

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Deena Doan 2F
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Joined: Sat Aug 17, 2019 12:17 am

Orbitals

Postby Deena Doan 2F » Sun Oct 20, 2019 4:56 pm

Hi,
In class, Lavelle went over some examples for the orbitals and he did Scandium as an example, but I am still a little confused on how why it is [Ar] 3d1, 4s2 and not the other way around.

Charisse Vu 1H
Posts: 101
Joined: Thu Jul 25, 2019 12:17 am

Re: Orbitals

Postby Charisse Vu 1H » Sun Oct 20, 2019 5:04 pm

The reason why Scandium is written as [Ar] 3d1 4s2 is because after the 20th element in the periodic table (Calcium), the 3d orbitals have a slightly lower energy than the 4s orbitals. Therefore, you would start filling the 3d orbitals until it is full. The 4s orbital is filled first because it is initially at a lower energy level, but after calcium, the energy level of 3d becomes slightly lower, and must fill up completely before the 4p orbital can be filled.

Maika Ngoie 1B
Posts: 97
Joined: Fri Aug 02, 2019 12:16 am

Re: Orbitals

Postby Maika Ngoie 1B » Sun Oct 20, 2019 6:16 pm

Charisse Vu 3E wrote:The reason why Scandium is written as [Ar] 3d1 4s2 is because after the 20th element in the periodic table (Calcium), the 3d orbitals have a slightly lower energy than the 4s orbitals. Therefore, you would start filling the 3d orbitals until it is full. The 4s orbital is filled first because it is initially at a lower energy level, but after calcium, the energy level of 3d becomes slightly lower, and must fill up completely before the 4p orbital can be filled.


In addition, I know in high school some people were taught that the configuration could also have been written as [Ar] 4s^2 3d^1, instead of [Ar] 3d^1 4s^2, however it is important to write the configuration from lowest to highest energy level because, later on when valence e- come into play, it will become much easier.

ATingin_3I
Posts: 51
Joined: Fri Aug 30, 2019 12:17 am

Re: Orbitals

Postby ATingin_3I » Sun Oct 20, 2019 6:23 pm

Why is it that each orbital can only hold 2 electrons max?

Sreyes_1C
Posts: 90
Joined: Fri Sep 28, 2018 12:19 am

Re: Orbitals

Postby Sreyes_1C » Sun Oct 20, 2019 7:37 pm

ATingin_3I wrote:Why is it that each orbital can only hold 2 electrons max?


I suppose its just a given that is defined by the Pauli exclusion rule, along with how the two electrons must have different spins

Jose Robles 1D
Posts: 100
Joined: Fri Aug 02, 2019 12:15 am

Re: Orbitals

Postby Jose Robles 1D » Sun Oct 20, 2019 7:42 pm

Can someone explain to me the specialty case of Chromium? With it having 4s1 instead of 4s2?

Deana Moghaddas 3E
Posts: 51
Joined: Fri Aug 30, 2019 12:17 am

Re: Orbitals

Postby Deana Moghaddas 3E » Sun Oct 20, 2019 7:57 pm

Jose Robles 1D wrote:Can someone explain to me the specialty case of Chromium? With it having 4s1 instead of 4s2?


For chromium, there are 4 levels (1,2,3,4). For chromium, the configuration at first glance would be 1s2,2s2,2p6,3s2,3p6,4s2,3d4.
As you can see, the 3rd energy level seems to be filled after the 4th. However, this isn't actually case. That's why we donate 4 as 4s1 to show that it hasn't been filled with electrons before the 3rd level.

Nuoya Jiang
Posts: 99
Joined: Sat Sep 14, 2019 12:17 am

Re: Orbitals

Postby Nuoya Jiang » Sun Oct 20, 2019 8:14 pm

So for Cr, 5 electrons in 5 3d orbitals and 1 electron in 4s has lower energy than 4 electrons in 3d, and 2 electron in 4s.

Eesha Sohail 1D
Posts: 100
Joined: Sat Aug 17, 2019 12:16 am

Re: Orbitals

Postby Eesha Sohail 1D » Sun Oct 20, 2019 8:37 pm

Maika Ngoie 3E wrote:
Charisse Vu 3E wrote:The reason why Scandium is written as [Ar] 3d1 4s2 is because after the 20th element in the periodic table (Calcium), the 3d orbitals have a slightly lower energy than the 4s orbitals. Therefore, you would start filling the 3d orbitals until it is full. The 4s orbital is filled first because it is initially at a lower energy level, but after calcium, the energy level of 3d becomes slightly lower, and must fill up completely before the 4p orbital can be filled.


In addition, I know in high school some people were taught that the configuration could also have been written as [Ar] 4s^2 3d^1, instead of [Ar] 3d^1 4s^2, however it is important to write the configuration from lowest to highest energy level because, later on when valence e- come into play, it will become much easier.


I didn't know this; thank you for clarifying. Would you happen to know why high schools teach it that way, and whether it matters for this class? I was always taught to order the orbitals the way they are filled according to the order of the periodic table.


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