## 4s and 3d

ElizabethP1L
Posts: 59
Joined: Wed Nov 15, 2017 3:01 am

### 4s and 3d

I know that the 4s orbital is actually higher than the 3d orbital and the exceptions in electron configurations that follow this rule. However, why is it that the 4s orbital is higher in energy? It's something I have just memorized, but I'd like to know the reason why. Thanks in advance! :)

Eli Esagoff_1I
Posts: 38
Joined: Fri Apr 06, 2018 11:02 am

### Re: 4s and 3d

I think that it is due to the difference in n. n=4 is a higher energy level than n=3.

Andre-1H
Posts: 39
Joined: Fri Apr 06, 2018 11:01 am

### Re: 4s and 3d

So, even though we are not responsible for the elements that occupy these orbitals, could we then apply this to the next row and say that 4d is lower in energy than 5s? Or would that be the only exception for this line of thinking?

ElizabethP1L
Posts: 59
Joined: Wed Nov 15, 2017 3:01 am

### Re: 4s and 3d

Andre-1H wrote:So, even though we are not responsible for the elements that occupy these orbitals, could we then apply this to the next row and say that 4d is lower in energy than 5s? Or would that be the only exception for this line of thinking?

Yes, that's right.

Jennifer Tuell 1B
Posts: 34
Joined: Fri Apr 06, 2018 11:05 am

### Re: 4s and 3d

I was confused about this too but if you think about it in terms of the lines he drew in class and how the gap gets smaller as you increase in energy level it makes sense that 4 is higher energy than 3 and 5 is higher than 4 and why when we draw electron configurations for ions we remove them from higher n=x