Cr^3+... [Ar]4s2,3d1 or [Ar]3d3

[Kneecoal]

---

Members do not see this ad.

My textbook says it's [Ar]3d3. Can someone explain why it jumps to d instead of filling up 4s first?

 

[NyCzPeter]

My textbook says it's [Ar]3d3. Can someone explain why it jumps to d instead of filling up 4s first?

Simple answer: thats just the way it is and just fill up the 4s first and you will never go wrong

Long: Its because the 4s shell is at a lower energy level than the 3d shell. So for the atom, filling up the 4s shell first is preferable in order to stay at the most stable state which is the lowest energy level. This will be the case for other levels aswell.

 

[Kneecoal]

Simple answer: thats just the way it is and just fill up the 4s first and you will never go wrong

Long: Its because the 4s shell is at a lower energy level than the 3d shell. So for the atom, filling up the 4s shell first is preferable in order to stay at the most stable state which is the lowest energy level. This will be the case for other levels aswell.

Are you sure? I was saying that the text makes no mention of 4s and skips right to the 3d's. I think I figured it out though, it looks like it only does this when the atom is an ion. So that's what I'll tell myself.

 

[kov82]

I don't think you read the question correctly shes asking why it wont fill the 4s first because of your explanation lol, what you said is correct, so why doesn't it fill the 4s first? the book says it fills 3d before 4s.

 

[karrotcake]

my guess is that having 3 electrons in 3d is more stable than having just 1 election in 3d, so they skipped 4s and put all the e- in 3d. correct me if i'm wrong though.

 

[Homing Swan]

When you make something an ion you take the electrons from the highest numbered orbital first. In this case the 4s come off before the 3d, even though the 3d electrons are in the highest energy orbital.

 

[sddat]

True: they come off of the 4s first because these are in the fourth and outermost shell. They feel the least pull from the nucleus and experience a core charge that allows them to be pulled off more readily than the increased core charge that the third shell feels.


The way you do these kind of problems is you first do the regular electron config for Cr

Cr: [Ar] 4s^2, 3d^4

Then you take off the electrons (3) from the outermost shell first and move inward.

Cr3+: [Ar] 3d^3

Draw a shell model for Cr and then pull off electrons, if you draw it correctly, you will see that it only makes sense to pull off the outermost electrons=valence electrons=4th shell.

 

[Kneecoal]

True: they come off of the 4s first because these are in the fourth and outermost shell. They feel the least pull from the nucleus and experience a core charge that allows them to be pulled off more readily than the increased core charge that the third shell feels.


The way you do these kind of problems is you first do the regular electron config for Cr

Cr: [Ar] 4s^2, 3d^4

Then you take off the electrons (3) from the outermost shell first and move inward.

Cr3+: [Ar] 3d^3

Draw a shell model for Cr and then pull off electrons, if you draw it correctly, you will see that it only makes sense to pull off the outermost electrons=valence electrons=4th shell.

thaaaaaank you. makes much more sense now.

 

[toiatoya]

Is this an example of hybridization? I could be wrong. But I thought that when the D shell pulls electrons from the S shell to fill itself, it creates an SP hybrid shell.

 

[FeralisExtremum]

True: they come off of the 4s first because these are in the fourth and outermost shell. They feel the least pull from the nucleus and experience a core charge that allows them to be pulled off more readily than the increased core charge that the third shell feels.


The way you do these kind of problems is you first do the regular electron config for Cr

Cr: [Ar] 4s^2, 3d^4

Then you take off the electrons (3) from the outermost shell first and move inward.

Cr3+: [Ar] 3d^3

Draw a shell model for Cr and then pull off electrons, if you draw it correctly, you will see that it only makes sense to pull off the outermost electrons=valence electrons=4th shell.

Nailed it! With transition metals, when removing electrons to make cation, you must remove from highest shell number first.

I have a related question: when adding electrons to make anions in the case of those elements that have jumped up ground states due to half/filled subshell stabilization, where do you add the next electron? I assume it follows the normal trend, so for example:

Cu : [Ar]4s1 3d10
Cu- : [Ar]4s2 3d10

Did I get this right?