Spectroscopic term of ground state electron configuration of Carbon atom

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Discussion Overview

The discussion revolves around the spectroscopic terms of the ground state electron configuration of the Carbon atom, specifically focusing on the derivation of possible terms from the 2p electrons. Participants explore the implications of the Pauli exclusion principle and the counting of multiplicities in relation to the terms derived.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant presents a derivation of possible terms for the 2p electrons in Carbon, listing terms such as ^{1}S_{0}, ^{1}D_{2}, and various ^{3}P states.
  • Another participant challenges the derivation, stating that not all constructed states comply with the Pauli exclusion principle and highlights the need to account for the correct number of states.
  • A question is raised about how to derive the total of 15 states from the multiplicities of the correct terms, with a focus on the spin multiplicities.
  • Further clarification is provided that the counting should focus on the multiplicities of J rather than S or L, indicating a need to consider how these multiplicities are distributed across different states.

Areas of Agreement / Disagreement

Participants do not reach consensus on the derivation of the terms, with ongoing debate about the application of the Pauli principle and the correct method for counting multiplicities.

Contextual Notes

There are limitations regarding the assumptions made in the derivation of terms and the dependence on the definitions of multiplicities. The discussion does not resolve the mathematical steps involved in the counting process.

boyu
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The ground state electron configuration of Carbon atom is 1s^{2}2s^{2}2p^{2}

For the electrons, 1s^{2}2s^{2}, L=0, S=0

So only consider electrons of 2p^{2}, and

s_{1}=s_{2}=1/2 ---> S=0,1
l_{1}=l_{2}=1 ---> L=0,1,2

For S=0, L=0; J=0, so we have ^{1}S_{0}
For S=0, L=1; J=1, so ^{1}P_{1}
For S=0, L=2; J=2, so ^{1}D_{2}

For S=1, L=0; J=1, so ^{3}S_{1}
For S=1, L=1; J=0,1,2, so ^{3}P_{0}, ^{3}P_{1}, ^{3}P_{2}
For S=1, L=2; J=1,2,3, so ^{3}D_{1}, ^{3}D_{2}, ^{3}D_{3}

The above is based on my derivation. However, the correct answer is actually:
^{1}S_{0}, ^{1}D_{2}, ^{3}P_{0}, ^{3}P_{1}, ^{3}P_{2}

My question is: where are all the other possible terms? Where is wrong in my derivation:
 
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Not all the states you are constructing are compartible with the Pauli principle.
Namely you have six p-type spin orbitals and there are 15 (2 out of 6) possibilities.
Counting the multiplicities of the correct states you should also get 15.
The total number of states of your approach is 36 which would result from filling up the p orbitals with hypothetically distinguishable electrons.
 
How to get 15 from counting the multiplicities from correct states? The spin multiplicities are 1, 1, 3, 3 & 3.
 
You have to count the multiplicities of J not of S or L. The multiplicities of S and L are dispersed over states with different J.
 
Many thanks! ^_^
 

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