Atomic Structure and Chemical Bonding: Hund՚s Rule and Stability of Completely Filled and Half-Filled Orbitals (For CBSE, ICSE, IAS, NET, NRA 2022)

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Hund՚s Rule

Stability of filled and half-filled orbitals

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 e. g. 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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