Electronic Configuration

The systematic arrangement of electrons in the subshells of an atom is called electronic configuration.  

Key Points to Remember  

1. Sub‑shells and Shells  

   - Electrons are arranged in shells (K, L, M, N) and subshells (s, p, d, f).  

2. Aufbau Principle  

   - Electrons fill orbitals in order of increasing energy levels (lowest first).  

3. Octet Rule  

   - Atoms tend to achieve 8 electrons in their outer shell for stability.  

4. Isoelectronic  

   - Different atoms/ions having the same number of electrons.  

5. Hund’s Rule  

   - Electrons occupy orbitals singly with parallel spins before pairing.  

6. Duplet Rule 

   - Atoms like hydrogen and helium achieve stability with 2 electrons in their outer shell.