Question

How can the ground state electron configuration for Mo be [Kr] 5s1 4d5
I thought it had to be 5s24d1 because you have to fill the 5s orbital before moving to the 4d orbital

Answer 1

Let me look at periodic table

Answer 2

Okay

Answer 3

is that the answer you got

Answer 4

It's apparently the correct answer
I thought it was 5s24d4

Answer 5

wait i remember that Mo has an expectation

Answer 6

is it because it's a d orbital element?

Answer 7

know what happens basically is that is takes an orbiatal from the s block and uses it to fill the the other electron because the are half filled orbitals. its goes the same with Cr as well.
it does it to make it more stable

Answer 8

okay that makes more sense.

Answer 9

the highest energy level has to be in the d orbital

Answer 10

orginally you would have has [Kr]5s^24d^4

Answer 11

but since the d is half filled and unstable you will take one from the 5s^2

now making it

[Kr]5s^14d^5

Answer 12

its just a rule to remember. let me find you a video on youtube

Answer 13

here https://www.youtube.com/watch?v=sMs6jpaluKI

Answer 14

okay
thank you so much!

Answer 15

Cr and Mo this applies to

Answer 16

no problem

Answer 17

did you get it

Answer 18

yeah i did
this makes a lot more sense now

Answer 19

Electrons are attracted to the nucleus, and hence, to pull an electron farther away from the nucleus, it would work against this attraction. Thus, electrons farther away from nucleus would have more energy than those closer. Also, this increases distance.

Now, in reference to your question, when a subshell is unpaired, it means lower overall energy. Without getting into the quantum mechanics of it, just keep in mind that this is what really shows electron behavior.
Also, paired electrons move together, while those that are unpaired stay farther away from each other. Since these "repel", paired electrons show more energy than unpaired. This explains why you have you have that configuration. I hope this makes sense.