AS Level Chemistry | Electronic Configuration EXPLAINED | Class 2 | Complete Lecture

This lecture explains the fundamental concepts of electronic configuration in AS Level Chemistry, covering the structure of atoms with shells, subshells (S, P, D, F), and orbitals. The instructor details how S orbitals are spherical, P orbitals are dumbbell-shaped, and explains the filling order of electrons: 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p → 6s. Key topics include the 4s orbital filling before 3d due to lower energy, and practical examples for elements like Lithium (1s² 2s¹), Sodium (1s² 2s² 2p⁶ 3s¹), Oxygen (1s² 2s² 2p⁶ 3s² 3p⁴), and Calcium (1s² 2s² 2p⁶ 3s² 3p⁶ 4s²). The lecture emphasizes that O-level configurations (shell-based) and A-level configurations (orbital-based) represent the same information but with different levels of detail.