Lewis Structure Tips: Central Atom & Expanded Octet Using Formal Charges

In this video, I go over the rules of formal charge and how we can use them to determine the best Lewis structure for a molecule. While symmetry can sometimes make it easy to decide on the central atom, that’s not always the case—especially when expanded octets are involved. Formal charge helps us figure out which Lewis structure is most stable and can even guide us in selecting the central atom. If you’re not yet comfortable drawing Lewis structures, I recommend starting with this video: https://youtu.be/3Cu8C0biqeE And if you need a refresher on how to assign formal charges, check out this step-by-step tutorial: https://www.youtube.com/watch?v=W-i3Z0ZgjSI You’ll learn: How formal charge can help identify the best Lewis structure What to consider when choosing a central atom When expanded octets make formal charge especially useful 👉 This video builds on prior knowledge of Lewis diagrams and formal charge basics. Best suited for high school, AP, IB, or first-year college chemistry students. 📒 Chapters 📒 0:00 Introduction 0:42 Formal Charge Rules 2:33 When to use formal charge to find the central atom 2:36 Example 1 – N₂O (nitrous oxide) and finding the central atom 6:20 Example 2 – SCN⁻ (thiocyanate ion) and finding the central atom 10:10 Example 3 – SO₂ (sulfur dioxide) and checking if expanded octet is needed 12:39 Example 4 – PO₄³⁻ (phosphate ion) and checking if expanded octet is needed Stay connected! 📞 Twitter (X): /ChemLessonsMona Instagram: /chem_lessons_with_Mona Website: http://mlchemistry.com/ 🔔 Subscribe for more chemistry lessons: / @chemlessonswithmona 📺 Watch the full video here: https://youtu.be/HCZvGgKONtI 🎥 Check out the playlist for more chemistry topics: https://youtube.com/playlist?list=PLMAhauS3prQRBdHYECaAU1hAjSh5iZqjd&si=SqSpm4ypUN64OCBj Thank you for watching! If you found this video helpful, please like it. Got any questions, suggestions, or feedback? Leave a comment below—I’d love to hear from you! #formalcharge #lewisstructure #chemistrytutorial #chemicalbonding #valenceelectrons #apchemistry #ibchemistry