Co2+ electron configuration

[anondukie]

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Why isn't it [Ar] 4s2 3d5 (considering the fact that half filled orbitals confer greater stability)?

Do all transitional metals behave this way?

Thanks!

 

[Apotheosis]

Carbon dioxide?

 

[aldol16]

Because the energy required to pair the electrons in 4s in this case is higher than the energy required to pair the electrons in 3d. It's all about relative energetics. The 3d and 4s orbitals are pretty similar in terms of energetics and putting electrons into those orbitals changes the relative energies. Electrons will always go to the orbital with the lowest energy first (taking into account pairing energy). It's not useful to memorize the exceptions to the rule though, and you should focus on other things.

 

[Necr0sis713]

Carbon dioxide?

He means Cobalt.

Its [Ar]3d7. You have to take 2 away from the s before d.

Half filled orbitals are more stable only when its a matter of when your close to it. otherwise, just fill it how it is. Usually for MCAT purposes, if its 3d4 or 3d9 then yeah, you can do that.

 

[anondukie]

So would this be considered an exception?

 

[aldol16]

So would this be considered an exception?

Well, no it really depends on the circumstance. If you have a gas phase Co(2+) ion, it would likely reorganize such that it reaches the lowest energy configuration. However, if you have solution phase Co(2+), it is likely to be solvated and ligated. If it's ligated, then it uses the s orbitals first to bond and so any s electrons are promoted to d.