Help with Electron-configuration

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Discussion Overview

The discussion centers around the electron configuration of chromium (Cr, Z=24) and the reasoning behind its specific configuration of ...3d5 4s1 rather than ...3d6. Participants explore the principles of electron configuration, including the roles of energy levels and stability of sub-shells, as well as the implications of experimental observations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about why chromium has the configuration ...3d5 4s1 instead of ...3d6, questioning whether this is simply an experimental observation or if there is a deeper explanation.
  • Another participant suggests referring to Pauli's exclusion principle and Hund's rule as part of the explanation for electron configurations.
  • A later reply indicates that the stability of half-filled and fully filled sub-shells is a known phenomenon, particularly in transition metals, and that configurations like s2d4 promoting to s1d5 are observed ground states.
  • It is noted that half-filled p-shells also exhibit anomalous stability, which can be observed in trends of experimental ionization energies.
  • Participants mention the importance of consulting additional resources, such as textbooks or online materials, for further understanding of periodic trends.

Areas of Agreement / Disagreement

Participants generally agree that the electron configuration of chromium is influenced by experimental observations and the stability of certain configurations, but there is no consensus on a singular explanation for the phenomenon.

Contextual Notes

Limitations include the lack of detailed discussion on the specific energy values associated with the configurations and the assumptions regarding the application of Pauli's and Hund's rules in this context.

abotiz
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Hi

Iam having a little problem understaning why some atoms are configured in a certain way.

I know that each sub-shell can take 2(2l+1) electrons, so for
s->2
p->6
d->10

But why e.g does the atom, Cr (Z=24) have the configuration : ...3d54s1 rather than ...3d6 ?

I know about that electrons in d sub-shell has higher energy than s and p, ( s<p<d )

Is this something we just have to accept because we know from experiments that Cr has the total energy X, so it can't possibly have ...3d6?

Or is there some other explanation?

Thanks!
 
Last edited:
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Please refer to Pauli rule and also hund's rule..[however one rule is usually applied in electronic configuratiions]
you will get the answer.
 
abotiz said:
Hi

Iam having a little problem understaning why some atoms are configured in a certain way.

I know that each sub-shell can take 2(2l+1) electrons, so for
s->2
p->6
d->10

But why e.g does the atom, Cr (Z=24) have the configuration : ...3d54s1 rather than ...3d6 ?

I know about that electrons in d sub-shell has higher energy than s and p, ( s<p<d )

Is this something we just have to accept because we know from experiments that Cr has the total energy X, so it can't possibly have ...3d6?

Or is there some other explanation?

Thanks!

Yes, this is from experiment. It is known that full and half-full angular momentum sub-shells show anomalous stabilities. It is best known for the transition metals, where the atoms with s2d4 configurations spontaneously promote to s1d5 configurations ... the latter configurations are the observed ground states in nature. Half-filled p-shells (i.e. p3) are also anomalously stable, as can be seen from the details of the trends in the experimental ionization energies of the elements.

You might want to google "periodic trends", or read about them in your textbook, for more information.

@ moderator: This thread probably belongs in the chemistry forum.
 
Thanks for the quick replies!

Also, Thank you SpectraCat for clearing that up for me =)
 

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