Which rule states that electron pairing in orbitals of the same subshell does not take place until each orbital is singly occupied with parallel spins?

💡 Solution & Explanation

Hund's rule of maximum multiplicity dictates that electron pairing in degenerate orbitals does not occur until each available orbital is singly occupied, which minimizes electron-electron repulsion and maximizes total spin. The Aufbau principle governs the sequential filling of orbitals based on increasing energy levels, while the Pauli exclusion principle restricts electrons in the same orbital to opposite spins. A related concept frequently tested in chemistry is the de Broglie wavelength formula for matter waves.