If neutral Calcium gains an electron...

[Rhino1000]

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... it (the electron) finds itself located in a d-orbital. Not in a p-orbital (TBR implies that the electron goes to a p-orbital). Right?

 

[Teleologist]

The book is right.

 

[premed1001]

-

 

[Rhino1000]

The book is right.

Why do you say? Scandium, the compound right after calcium, begins filling its d-orbital. Why would calcium randomly start filling its p?

 

[Teleologist]

Scandium begins filling its d-orbital? Nope. It's d-orbital has already been populated. After its d-orbital is populated its 4s-orbital gets populated.

 

[Rhino1000]

Scandium begins filling its d-orbital? Nope. It's d-orbital has already been populated. After its d-orbital is populated its 4s-orbital gets populated.

Scandium, if it were to become an anion (like this entire thread is about), would populate its d-orbital with the extra electron, not its 4s orbital. Isn't this the case?

 

[Teleologist]

Scandium, if it were to become an anion (like this entire thread is about), would populate its d-orbital with the extra electron, not its 4s orbital. Isn't this the case?

Yes. This is because electrons populate the lowest energy levels first.

The book's still right, you know.

 

[Rhino1000]

Yes. This is because electrons populate the lowest energy levels first.

So then if calcium were to become an anion, it would populate its d-orbital before its 4p orbital, or is there a reason that it wouldn't do this, but scandium would?

 

[Teleologist]

So then if calcium were to become an anion, it would populate its d-orbital before its 4p orbital, or is there a reason that it wouldn't do this, but scandium would?

Because its d-orbital is a 3d orbital, which is lower in energy than a 4p orbital.

 

[Rhino1000]

Because its d-orbital is a 3d orbital, which is lower in energy than a 4p orbital.

I thought the electron would be more likely to go to the lesser-energy orbitals? If the d-orbital is lower in energy as you say, then wouldn't the electron rather populate it rather than the p-orbital?

 

[Teleologist]

That's what I just said.

 

[Rhino1000]

Yes. This is because electrons populate the lowest energy levels first.

The book's still right, you know.

Why do you say the book's still right? The book said that the p-orbital would fill, but you just said that it's correct that the d-orbital, rather, would fill, but then went on to say the book, which seems to contradict you, is "still right?"

 

[Rhino1000]

That's what I just said.

So then you agree that the book is wrong?

 

[Teleologist]

So then you agree that the book is wrong?

Yes; I think I'm in error here. Good catch! I'll have to think about this a bit more though.

 

[Rhino1000]

Yes; I think I'm in error here. Good catch! I'll have to think about this a bit more though.

Ok. Thanks for the replies though! I think that it's likely BR has an error.

 

[DrknoSDN]

This is the reason TBR mentions calcium anions going into p orbitals.
Structural properties of the negative calcium ion: Binding energies and fine-structure splitting. ==> http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.76.744

Abstract: "The binding energies of the 4s24pP2 ground state in Ca− have been determined by means of state-selective photoionization of Ca atoms produced in s-wave photodetachment ... The sensitivity of the detection technique applied has also made it possible to disprove previous claims for the observation of a metastable 4s 4p2 4P state in Ca−."

I don't know anything about metastable states of calcium, but apparently it's of interest to someone. There is still current (2010) research about the chemistry of calcium anions. None of them talk about electrons adding to the D subshell. It may just be to high energy and Ca has too low electron affinity.
Calcium has the lowest electron affinity of any element that is capable of forming a stable anion that won't auto ionize back to neutral.
Source: http://en.wikipedia.org/wiki/Electron_affinity_(data_page) 2.37kJ/mol. Reference citation is [13]

Strange that TBR would mention any of that. Probably just safer to pretend it adds to D... 😕

 

[Rhino1000]

This is the reason TBR mentions calcium anions going into p orbitals.
Structural properties of the negative calcium ion: Binding energies and fine-structure splitting. ==> http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.76.744

Abstract: "The binding energies of the 4s^2 4p^2 P ground state in Ca− have been determined by means of state-selective photoionization of Ca atoms produced in s-wave photodetachment ... The sensitivity of the detection technique applied has also made it possible to disprove previous claims for the observation of a metastable 4s 4p2 4P state in Ca−."

I don't know anything about metastable states of calcium, but apparently it's of interest to someone. There is still current (2010) research about the chemistry of calcium anions. None of them talk about electrons adding to the D subshell. It may just be to high energy and Ca has too low electron affinity.
Calcium has the lowest electron affinity of any element that is capable of forming a stable anion that won't auto ionize back to neutral.
Source: http://en.wikipedia.org/wiki/Electron_affinity_(data_page) 2.37kJ/mol. Reference citation is [13]

Strange that TBR would mention any of that. Probably just safer to pretend it adds to D... 😕

What was that that I just read? Lol. I don't see how there can be two electrons in the 4p orbital in a simple calcium anion. Electrons even being present in that orbital is news to me, let alone two of them. Thanks for the good work. I might just accept this one by faith. By the way, are you saying that TBR literally mentioned this type of research in citation form, or are you saying you wonder why TBR would mention the p-orbital placement of an additional electron in calcium (referring to the sum of your first and last sentences)?

 

[DrknoSDN]

What was that that I just read? Lol. I don't see how there can be two electrons in the 4p orbital in a simple calcium anion. Electrons even being present in that orbital is news to me, let alone two of them. Thanks for the good work. I might just accept this one by faith. By the way, are you saying that TBR literally mentioned this type of research in citation form, or are you saying you wonder why TBR would mention the p-orbital placement of an additional electron in calcium (referring to the sum of your first and last sentences)?

I don't know why TBR would bring up this obscure case. I understand mentioning common deviations from aufbau principle but this example seems less well known than some other ones that may show up on MCAT.

if you just google "Calclium 4s4p2" you get a lot of research.
Harvard: "Ca- and its elusive properties" ==> http://adsabs.harvard.edu/full/1992AuJPh..45..293P
Elsevier: "Atomic negative ions: structure, dynamics and collisions" ==> http://www.physics.uoguelph.ca/~rlb/phys710/PhysRep394_157.pdf

Basically Calcium and other negative ions can use the p subshell over d.

The subject is in a research phase and I don't know why TBR thought that was relevant information for the MCAT. Never heard anything about it in any of my studies or texts until now.
I suppose it's better than generalizing something and being wrong factually.
I'd rather read abstract things that are accurate instead of spending 20 minutes to determine the book was wrong. TBR was right! 😀

 

[Mrs.Buckeye1992]

I don't know why TBR would bring up this obscure case.

Because it's TBR.