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What is HUND’s Rule?

by Team Goseeko

According to Hund’s rule, all orbitals will be once filled before any electron is double filled. Therefore, two p orbital get one electron and one will have 2 electrons. Hund’s rule also specifies that all of the unpaired electrons must have the same spin. In keeping with practice, the unpaired electrons are drawn as “spin-up”


  • Before the double occupation of any orbital, every orbital in the sub level is singly occupied.
  • For the maximization of total spin, all electrons in a single occupancy orbital have the same spin.

An electron does not pair with another electron that is present in a half-filled orbital, because the electrons will fill the orbitals with similar energy.

In the ground state many in paired electrons are present in atoms. When two electrons come in contact, they would show the same property as that of a magnet. The electrons initially move far away from one another before they pair up

Hund’s Rule of Maximum Multiplicity

Hund’s Rule of Maximum Multiplicity rule states that for a given electron configuration, the term with maximum multiplicity falls lowest in energy. According to this rule electron pairing in p, d and f orbitals cannot occur until each orbital of a given subshell contains one electron each or is singly occupied.

Hund Rule states that:

1. Every orbital is occupied singly and then later dubbly occupied in the    sublevel.

2. Identical spin is predominant in the electrons that are present in singly occupied orbitals.

Explanation of Hund’s Rule

Before pairing up the electrons enter an empty orbital. As the electrons are negatively charged, they repel each other,

therefore the electrons do not share orbitals to reduce repulsion.

When allowing electrons to orbitals, an electron seeks to fill the orbitals with comparable energy (also called as degenerate orbitals) before joining with another electron in a half-filled orbital.

Atoms at ground state tend to have as many unpaired electrons, in reflecting this process .

Electrons tend to reduce objection by occupying their own orbitals, rather than receiving or accepting an orbital with another electron.

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