Hund’s Rule Definition Example & Application

Definition

Hund’s rule refers to a set of rules that are used as the guidelines for filling electrons in the orbital and spin of an electron in the orbital.

Hund’s rule states that "In the orbitals of the same subshell, electrons are filled singly first before pairing starts."

Alternatively, Hund’s rule states that electrons don’t pair up in a subshell until they are occupied by a single spin.

Example

Let us take an example of filling electrons in a nitrogen atom.

The electronic configuration of nitrogen is 1s2 2s2 2p3.

There are two possibilities of filling the electrons in 2p orbital

Rule of Maximum Multiplicity

According to Hund’s rule, while filling up electrons in degenerate orbitals electrons first fill up singly then only start to pair up. It means atomic orbitals tend to have more unpaired electrons as far as possible. A greater number of unpaired electrons offer maximum multiplicity.

Application of hund’s rule

It gives us an idea of filling electrons in the atomic orbitals. It gives an idea about which arrangement of electrons is correct or more stable.

Limitations of hund’s rule

The limitation of Hund’s rule is that it can not be used to predict the lowest energy configuration.

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