@naytuntun22: Electronic configuration is the foundation of chemistry. Mastering this makes every other topic much easier! Here are the most important notes you must remember for your exams 👇 ✅ 3 Main Rules • Aufbau Principle – Electrons fill orbitals starting from the lowest energy level first, then move to higher energy levels. • Pauli Exclusion Principle – Each orbital can hold a maximum of 2 electrons, and they must have opposite spins. • Hund’s Rule – For orbitals of equal energy, electrons occupy them singly first, then pair up. ✅ Order of Filling Orbitals 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → … ⚠️ Important: 4s has lower energy than 3d, so it fills before 3d. ✅ Maximum Electrons per Subshell • s = 2 electrons • p = 6 electrons • d = 10 electrons • f = 14 electrons ✅ Quick Examples • H = 1s¹ • O = 1s² 2s² 2p⁴ • K = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ • Ca = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² Keep these rules in mind and you’ll never go wrong when writing configurations! Perfect for scoring high marks in exams 💯 📚 Study with Nay Nay Follow for more exam‑focused notes and lessons ✨ #AufbauPrinciple #PauliExclusionPrinciple #HundsRule #ExamPreparation #StudyWithNayNay

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