half/full d orbitals

[laczlacylaci]

when it is s2d4 it wants to become half full to s1d5
or
when it is s2d9 it wants to become full to s1d10
does this rule only apply to when d oribtal is d4 and d9? (ie. d3 wouldn't become half full, right)

and when it does want to become half/full the previous orbital needs to have an electron ready correct? (ie. s1d4 is incorrect and actually should be s2d3? b/c of aufbau's, correct?)

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[bobeanie95]

The D level has 5 orbitals to hold 10 electrons total. The exceptions are for Chromium and Copper, one of the electrons from the 4s orbital will go into the 3d orbital to maintain stability. Chromium will then be 4s13d5 and copper is 4s13d10. Note that this wont happen with other molecules that have different number of valence electrons. In other words, you won't see molecules completely emptying their 4s to have a half/full filled d level.

 

[laczlacylaci]

The D level has 5 orbitals to hold 10 electrons total. The exceptions are for Chromium and Copper, one of the electrons from the 4s orbital will go into the 3d orbital to maintain stability. Chromium will then be 4s13d5 and copper is 4s13d10. Note that this wont happen with other molecules that have different number of valence electrons. In other words, you won't see molecules completely emptying their 4s to have a half/full filled d level.

Ohhhh, so only chromium and copper will follow this half/full rule, is that correct?

 

[theonlytycrane]

I think it can happen for any d5/d10 jumping situation (Mo or Ag). Also, electrons are lost from outer s before outer d like if Mn lost an electron.

 

[bobeanie95]

Yes, it can be any molecule that has the same number of valence electrons as Chromium and Copper, in other words in the same group

 

[laczlacylaci]

I think it can happen for any d5/d10 jumping situation (Mo or Ag). Also, electrons are lost from outer s before outer d like if Mn lost an electron.

Yes, it can be any molecule that has the same number of valence electrons as Chromium and Copper, in other words in the same group

Quick brush up. This rule applies to other elements than just Cr and Cu?

I think I don't understand when you said the same group.
For example: Co(II), same group as Cu. the configuration of it would be [Ar]3d7 and not [Ar]4s2 3d5...

Thank you!

 

[deleted585480]

would like clarification on this as well.. this has always stumped me.

 

[theonlytycrane]

Quick brush up. This rule applies to other elements than just Cr and Cu?

I think I don't understand when you said the same group.
For example: Co(II), same group as Cu. the configuration of it would be [Ar]3d7 and not [Ar]4s2 3d5...

Thank you!

"group" is the vertical column on the periodic table and "period" is across. Co and Cu are in the same period, but not the same group.

When losing electrons, lose from the outer s before the outer d. In the case of Co(II), 2 electrons are lost from 4s before 3d. 4s filled first, but 4s also loses first because 4 is bigger than 3.

When an atom has a d4 or d9 configuration, one of the s electrons can jump up to fill the d orbital to create d5 or d10 stability. (I'm not sure why exactly, I just accept it as MCAT truth).

So for Cr we would expect [Ar]4s1 3d5 and for Mo (same group) we would expect [Kr]5s1 4d5.

So the 2 electron configuration tricks are: lose outer s before outer d, and look out for d5 / d10 stability.

 

[laczlacylaci]

"group" is the vertical column on the periodic table and "period" is across. Co and Cu are in the same period, but not the same group.

When losing electrons, lose from the outer s before the outer d. In the case of Co(II), 2 electrons are lost from 4s before 3d. 4s filled first, but 4s also loses first because 4 is bigger than 3.

When an atom has a d4 or d9 configuration, one of the s electrons can jump up to fill the d orbital to create d5 or d10 stability. (I'm not sure why exactly, I just accept it as MCAT truth).

So for Cr we would expect [Ar]4s1 3d5 and for Mo (same group) we would expect [Kr]5s1 4d5.

So the 2 electron configuration tricks are: lose outer s before outer d, and look out for d5 / d10 stability.

Got it. I confused Cr and Cd for a sec.
So Cr, Mo, W, Sg (in one group) & Co, Rh, Os, Hs (another group) should all exhibit this half/full d orbital rule.

 

[theonlytycrane]

Got it. I confused Cr and Cd for a sec.
So Cr, Mo, W, Sg (in one group) & Co, Rh, Os, Hs (another group) should all exhibit this half/full d orbital rule.

I think you mean Cu, Ag, Au, and Rg? But I think so yes.

 

[laczlacylaci]

I think you mean Cu, Ag, Au, and Rg? But I think so yes.

lmao I'm an idiot. Yes I meant that group. crashing before my exam.

 

[theonlytycrane]

lmao I'm an idiot. Yes I meant that group. crashing before my exam.

I know how hard you've been studying. Make sure to schedule in lighter days or break days to rejuvenate closer to your date.

 

[aldol16]

You will not be tested on minutiae like this. Whether an electron is "promoted" to make a half-full/full d-orbital depends on the difference between the pairing energy and the orbital energy. If the pairing energy is smaller than the difference in orbital energies, the electron will stay in the s shell. If the pairing energy is greater than the difference in orbital energies, the electron will move into the d shell. Electrons want to have the lowest possible energy in the ground state.

Add to this the fact that half-full and full d-orbitals are unusually stable (due in some part to the spherically-symmetric distribution of electrons) and you get the odd "exceptions" to the filling rule. But when you think about electronics, it's not an "exception" at all!