A student records an orbital diagram for a neutral atom in its ground state with atomic number $Z = 7$. The first two energy sublevels are completely filled with paired electrons of opposite spins, whereas in the $2p$ sublevel, two electrons share a single degenerate orbital with opposing spins and the third electron occupies a second orbital, leaving the third degenerate orbital completely unoccupied. Which fundamental principle or rule of electron configuration is violated by this arrangement, and what change is required to reach the true ground state?

A) The Aufbau principle is violated; one electron must be promoted to the $3s$ subshell before completing the $2p$ subshell.

B) The Pauli exclusion principle is violated; the two paired electrons in the same orbital must possess identical spin quantum numbers.

C) The Aufbau principle is violated; all degenerate orbitals must have their spins reversed before another subshell can accept electrons.

D) Hund's rule is violated; each degenerate $2p$ orbital must receive one electron with parallel spin before any pairing occurs.

Aufbau principle, Pauli exclusion principle and Hund's rule Transitional Reasoning Practice

Chemistry · Atomic Structure · Chemistry · Electrons in Atoms

1 Chemistry practice questions on Aufbau principle, Pauli exclusion principle and Hund's rule. Questions that build towards applied reasoning.

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Atomic Structure · Chemistry

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