Question

what rule or principle is violated here? 1s 2s 2p aufbau principle pauli exclusion principle hunds rule

Explanation:

Hund's Rule states that electrons in degenerate orbitals fill singly first with parallel spins before pairing up. In the given 2p - orbital configuration, electrons should first occupy each 2p - orbital singly with the same spin before pairing, but here they are paired prematurely, violating Hund's Rule. The Aufbau Principle deals with the order of filling orbitals (lower - energy orbitals first), and the Pauli Exclusion Principle states that no two electrons in an atom can have the same set of four quantum numbers (related to electron spin and orbital occupancy in a different way than the violation shown here).

Answer:

C. Hund's Rule