Which rule states that pairing of electrons in orbitals of degenerate energy levels does not take place until each orbital is singly occupied?

💡 Solution & Explanation

Hund's Rule of Maximum Multiplicity dictates that every available orbital within a given subshell must be occupied singly by electrons with parallel spins before any single orbital undergoes pairing with a second electron of opposite spin. The Pauli Exclusion Principle restricts any two electrons in the same atom from sharing an identical set of all four quantum numbers, whereas the Aufbau Principle governs the sequential filling of orbitals in increasing order of energy. Quantum mechanical rules governing atomic electron configurations are fundamental chemical concepts.