Problem: The following sets of quantum numbers, listed in the order n, ℓ, mℓ, and ms, were written for the last electrons added to an atom. Identify which sets are valid and classify the others by the rule or principle that is violated.When writing the ground-state electron configuration of a many-electron atom, three main rules must be followed:The aufbau principle: Electrons are added to the lowest energy orbitals availableThe Pauli exclusion principle: No two electrons in an atom can have the same set of four quantum numbers (n, ℓ, mℓ, and ms)Hund's rule: For degenerate orbitals, the lowest energy state is attained when the number of electrons with the same spin is maximized. So for a degenerate set of orbitals, one electron goes into each orbital until all the orbitals of the subshell are half-filled. Once all the orbitals of the subshell are half-filled the pairing of electrons can take place.Note that aufbau is the German word for "building up."

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The following sets of quantum numbers, listed in the order n, ℓ, m, and ms, were written for the last electrons added to an atom. Identify which sets are valid and classify the others by the rule or principle that is violated.



When writing the ground-state electron configuration of a many-electron atom, three main rules must be followed:

  • The aufbau principle: Electrons are added to the lowest energy orbitals available
  • The Pauli exclusion principle: No two electrons in an atom can have the same set of four quantum numbers (n, ℓ, m, and ms)
  • Hund's rule: For degenerate orbitals, the lowest energy state is attained when the number of electrons with the same spin is maximized. So for a degenerate set of orbitals, one electron goes into each orbital until all the orbitals of the subshell are half-filled. Once all the orbitals of the subshell are half-filled the pairing of electrons can take place.

Note that aufbau is the German word for "building up."

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