Question

According to which principle/rule, electron pairing starts only when all the orbitals of same energy are singly occupied?

• A. Pauli exclusion principle
• B. Heisenberg uncertainty principle
• C. Hund's rule
• D. Aufbau principle

Answer 1

The correct option is C Hund's rule

According to Hund's rule:

- Electron pairing starts only when all the orbitals of same energy are singly occupied with one electron.
- All of the electrons in singly occupied orbitals have the same spin (to maximize total spin).

For example, the electronic distribution in orbitals of nitrogen atom is as follows