Quantum Numbers & Electron Configuration — Every Electron Has an Address! (All Problems Solved)

Every electron in an atom has its own unique “address”, and in this video you’ll learn exactly how to read it! 🔬⚛️ We start with the four quantum numbers: Principal quantum number (n): the shell and its energy level Azimuthal quantum number (l): the sublevel and its shape (s, p, d, f) Magnetic quantum number (mₗ): the orientation of the orbital in space Spin quantum number (mₛ): spin up (+½) or spin down (−½) Then we cover the three rules for distributing electrons: ✅ Aufbau (building-up) principle and the (n + l) rule: why 4s fills before 3d ✅ Hund’s rule: single electrons with parallel spins before pairing ✅ Pauli exclusion principle: at most two electrons per orbital, with opposite spins 📝 Every problem is solved step by step: Electron configurations of Na, Cl, Ca and Fe Quantum numbers of the last electron for Be, N, O, Na, Cl, Ca, Mn, Ni and Zn Full analysis of an element with Z = 13 and A = 27 (aluminum) Period, group, type and valency of C, Ne, Mg, Si, Cl, K and Kr Electron configurations of the ions Fe²⁺, O²⁻, S²⁻ and Ca²⁺ Why chromium and copper end in 4s¹ (half-filled and completely filled d sublevels) Ground state, excited state or impossible configuration? 🎧 English narration with Arabic subtitles | شرح بالإنجليزية مع ترجمة عربية كاملة ⏱️ Chapters 0:00 Intro 0:19 The four quantum numbers 0:42 Principal quantum number (n) 1:16 Azimuthal quantum number (l) & orbital shapes 2:03 Magnetic quantum number (mₗ) 2:47 Spin quantum number (mₛ) 3:16 Summary table (n = 1 to 4) 3:27 Aufbau principle & the (n + l) rule 4:28 Problem 1: electron configurations 5:00 Hund’s rule 5:30 Pauli exclusion principle 5:47 Orbital diagrams from H to Ne 6:18 Quantum numbers of the last electron: method 7:01 Worked examples: Be, N, O, Na, Cl, Ca, Mn, Ni, Zn 10:02 Problem 2: Z = 13, A = 27 10:50 Period, group, type & valency: rules 11:39 Examples: C, Ne, Mg, Si, Cl, K, Kr 14:41 Electron configuration of ions 15:51 Extra-stable configurations: Cr and Cu 16:29 Question 1: why 4s¹ for Cr and Cu? 16:59 Question 2: ground, excited or impossible? 18:14 Recap 18:45 Like, subscribe & share 👍 If this video helped you, please LIKE, SUBSCRIBE, turn on the 🔔, and SHARE it with your classmates! 💬 Tell us in the comments which topic you want next.