Question

which rule was broken? aufbau principle hunds rule pauli exclusion principle drag

Explanation:

The Aufbau principle states that electrons fill lower - energy orbitals before higher - energy ones. Hund's rule requires that electrons in degenerate orbitals first fill each orbital singly with parallel spins. The Pauli exclusion principle says that no two electrons in an atom can have the same set of four quantum numbers. In the given electron - filling diagram, electrons are paired in the 2p orbitals before all 2p orbitals are singly occupied, which violates Hund's rule.

Answer:

Hund's Rule