Credit: Image courtesy of Journal of the American Chemical Society
The application of Hund’s First Rule to berkelium(IV) leads to the expectation of an even distribution of parallel electrons (purple and peach) in each of the orbital subshells. This rule assumes that electron-electron repulsion is much larger than spin-orbit coupling. This rule does not hold true in heavy elements and a large deviation from the rule is observed in berkelium(IV) iodate.