# NIOS Chemistry Lesson 2 Atomic Structure and Chemical Bonding Part 3

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### Hund’S Rule

Stability of completely filled and half filled orbitals

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

The exactly half-filled and fully filled orbitals have greater stability than other configurations. The reason for their stability are 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.