List of Hund's rules

In atomic physics, Hund's rules are rules that determine how the electrons in an atom work. Often, the first of Hund's rules is most often mentioned. The first rule of Hund's rules is so important in chemistry that it is simply just called "Hund's rule".

Below is a brief description of Hund's rules.

1. In each orbital, one electron is placed in each orbital before pairing. For example, if the $2p$ orbital is filled to $2p^{3}$, all of the electrons will not be paired. The $2p$ orbital will continue to be filled until it reaches 6 electrons, making that orbital full.
2. If all electrons are orbiting in the same direction, some of them will be orbiting the opposite direction.
3. Energy will shift due to spinning of the electrons.