Hund’s Rule

A set of orbitals is degenerate if they are all at the same energy level. Quick note, degenerate does not mean bad.

When electrons fill degenerate levels, each orbital receives one electron until all the unoccupied orbitals are filled, then the next electron will go into an occupied otbital.

Appendix A

Two other rules are needed when filling electrons into orbitals:

• A maximum of two electrons will go into one orbital
• The electrons in an orbital are such that one has the opposite spin of the other.