## electron configuration of chromium? [ENDORSED]

Alondra Juarez section 1E
Posts: 47
Joined: Fri Sep 29, 2017 7:03 am

### electron configuration of chromium?

I worked on a problem to find out the ground state electron configuration for chromium and was told it is [Ar] 3d^3 4s^1 why isn't it 3d^4 if it is in the fourth box of the d-block?

MariahClark 2F
Posts: 60
Joined: Wed Nov 15, 2017 3:04 am

### Re: electron configuration of chromium?  [ENDORSED]

The way I know Cr's electron configuration to be is: [Ar] 3d^5 4s^1... this is still different from the regular way we would find electron configuration for it, which is [Ar] 3d^4 4s^2 and it is one of the exceptions. In order for Cr to be more stable it would rather have its d and s energy level be half full rather than s be full and d only have 4 out of 10 electrons filled in. Hence is why an electron is taken from the 4s level and put in the 3d level to make them both half full. Cr is just more stable this way.

Posts: 32
Joined: Fri Apr 06, 2018 11:05 am
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### Re: electron configuration of chromium?

Copper also acts similarly to Chromium because it is in the ninth position in the d-block. Therefore instead of its electron's configuration being [Ar] 3d^9 4s^2 it would actually be [Ar] 3d^10 4s^1 because it is more stable.

304984981
Posts: 28
Joined: Fri Apr 06, 2018 11:05 am

### Re: electron configuration of chromium?

copper and chromium are the only 2 exceptions that disobeys the regular rules you need to remember for this course.
For copper and chromium, the 3d orbital is half-filled or fully-filled since they wanna get more stable.

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