Atomic Structure and Chemical Bonding: Hund's Rule and Stability of Completely Filled and Half-Filled Orbitals

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Hund’S Rule

Stability of completely filled and half filled orbitals

Image of Hund's Rule

Image of Hund's Rule

  • This rule states that if 2 or more degenerate (i.e. same energy) orbitals are available, one electron goes into each until all of them are half full before pairing up.

  • For eg. in a bus one in relation to the analogy of filling seats in a bus; everyone finds their own seat, and only when all the seats are half full do, they start sitting together.

Stability of Completely Filled and Half- Filled Orbitals

Stability of Completely Filled and Half Filled Orbitals

  • The exactly half-filled and fully filled orbitals have greater stability than other configurations. The reason for their stability is symmetry and exchange energy.

  • The half-filled and fully filled orbitals are more symmetrical than any other configuration and symmetry leads to greater stability.

  • Full filled orbitals are more stable than half filled orbitals.

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