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### Switching 3d and 4s

Posted: Sun May 06, 2018 10:28 am
Even though d has a higher energy than s, I was told that for some configurations you have to switch 3d to be in front of 4s. When is this the case?

### Re: Switching 3d and 4s

Posted: Sun May 06, 2018 12:09 pm
3d actually does not have a higher energy than 4s, which is why it must be placed before 4s and 4p when writing out the electron configurations.
If you follow the pattern across the periodic table, you will be able to see the corresponding energy levels. There is 3s and 3p before 3d, so that means that 3d would have a lower energy than 4s and 4p.

### Re: Switching 3d and 4s

Posted: Sun May 06, 2018 12:31 pm
Just to clarify, this means that for any element with an electron configuration that has both s and d orbitals, the d orbital would come before the s and followed by p. But for elements without the d orbital it would be the s orbital first. Correct me if I am wrong. And also s orbitals have higher energy than d orbitals?

### Re: Switching 3d and 4s

Posted: Sun May 06, 2018 1:18 pm
Odalys Cuevas 1C wrote:Just to clarify, this means that for any element with an electron configuration that has both s and d orbitals, the d orbital would come before the s and followed by p. But for elements without the d orbital it would be the s orbital first. Correct me if I am wrong. And also s orbitals have higher energy than d orbitals?

Yes, the d orbital would come before the s orbital and then followed by the p. And if there is no d orbital, it would be the s orbital first.
S orbitals do have higher energy than d orbitals, which is why d orbitals come before s orbitals. For example, you would put 3d before 4s.

### Re: Switching 3d and 4s

Posted: Sun May 06, 2018 2:30 pm
When d is occupied by electrons then it becomes lower in energy than s which is when you would put it before s. So elements with 21 electrons or more would have the d come before the s because this is when we first see d become occupied by electrons.

### Re: Switching 3d and 4s

Posted: Sun May 06, 2018 10:40 pm
An 4s orbital has higher energy than a 3d orbital so you would write the 3d orbital before the 4s orbital. This works the same way with the 4d and 5s orbitals and so on. Hope this helps!

### Re: Switching 3d and 4s

Posted: Sun May 13, 2018 1:16 pm
The 4S orbital has higher energy than the 3D orbital, which is why you write it afterwards. Also, it is important to note that since the energy in the 4S orbital is higher, the electrons from that orbital will be removed before electrons in the 3D orbital are removed