What does Hund's rule state about the filling of orbitals?

Hund's rule specifically addresses the way electrons occupy degenerate orbitals (orbitals that have the same energy level). According to this rule, when electrons fill these orbitals, they first occupy each orbital singly before any start to pair up. This minimizes electron-electron repulsions, as electrons are negatively charged and naturally repel each other. By filling orbitals singly first, the system achieves a more stable configuration.

This principle is essential in understanding the electron configuration of atoms and helps predict the behavior of elements in chemical reactions. The requirement that each orbital in a set be singly filled before any have paired electrons leads to a more stable electron arrangement and helps explain the observed magnetic properties of elements.

In contrast, the other options either misinterpret the fill order of orbitals or apply rules that do not align with Hund's principle. This makes the correct choice clear, as it encapsulates the core idea of how electrons fill orbitals within the same energy level.