3d and 4s orbitals

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Xinyi_Yan_3L
Posts: 21
Joined: Wed Sep 21, 2016 2:56 pm

3d and 4s orbitals

Postby Xinyi_Yan_3L » Sat Oct 15, 2016 3:38 pm

I learnt in class that 3d orbital has lower energy level than the 4s orbital. Then why electrons first fill in 4s orbitals before they go to 3d?

Aileen Nguyen 3N
Posts: 26
Joined: Wed Sep 21, 2016 2:56 pm
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Re: 3d and 4s orbitals

Postby Aileen Nguyen 3N » Sat Oct 15, 2016 3:48 pm

3D is only lower in energy than 4s after the 4s orbital is occupied

Jeannie_Kim_1I
Posts: 23
Joined: Fri Jul 15, 2016 3:00 am

Re: 3d and 4s orbitals

Postby Jeannie_Kim_1I » Sun Oct 16, 2016 10:03 am

4s orbitals are lower in energy when there are no electrons in 3d orbitals, which is why 4s gets filled in first (according to the Aufbau principle). When 3d orbitals start filling up with electrons, they become lower in energy, and 4s orbitals become higher in energy. This is why 3d comes before 4s when we write our electron configurations.


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