Defining Degenerate Orbitals:

Degenerate orbitals refer to electron orbitals that share the same energy level.

According to the Aufbau principle, electrons fill up lower energy levels before moving to higher ones. Hund’s rule further elaborates that degenerate orbitals are populated evenly before electrons occupy higher energy levels. These rules, along with Pauli’s exclusion principle, guide how electrons are distributed among orbitals.

Navigating this article:

• • The Aufbau Principle
  • Hund’s rule
  • Example of Degenerate Orbitals
  • Diagram and Explanation of Degenerate Orbitals

The Aufbau Principle:

The Aufbau principle asserts that in an atom's ground state, electrons fill the lowest available energy levels first, before occupying higher ones. For instance, the 2s subshell is populated only after the 1s shell is filled, leading to the most stable electron configuration.

Hund’s Rule:

According to Hund’s rule , the maximum number of unpaired electrons with the same spin exists in the ground state electron configuration of any electron subshell. Friedrich Hund introduced this rule in 1927, which is instrumental in determining the ground state of a molecule or atom.

Example of Degenerate Orbitals:

Consider the d orbital, which has 5 degenerate orbitals. Initially, each of these orbitals is occupied by one electron. The second electron entering each orbital will have an opposite spin. In this way, all orbitals are filled, accommodating a total of ten electrons.

Diagram and Explanation of Degenerate Orbitals:

The 2p sublevel contains degenerate orbitals, meaning the 2p_x, 2p_y, and 2p_z orbitals all possess the same energy, as depicted in the diagram below. Likewise, the 3p_x, 3p_y, and 3p_z are also degenerate orbitals. At the 3d energy level, the 3d_xy, 3d_xz, 3d_yz, 3d_{x2 – y2}, and 3d_z2 are degenerate orbitals , all having the same energy.

Degeneracy refers to the total number of distinct states possessing the same energy, also known as the degree of degeneracy.

• • • • p orbitals have a degeneracy degree of 3
      • d orbitals have a degeneracy degree of 5
      • f orbitals have a degeneracy degree of 7

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