Formal Charge Calculation

🔥 Formal Charge Rescue Plan

📐 Formula: FC = Valence – (Lone Pairs + ½ Bonding Electrons)

✅ If all atoms have the same formal charge, compare where the charge sits. Give negative FC to the most electronegative atom.

🧪 “Zero formal charge ≠ equal stability!”

🔥 Top 3 Formal Charge Mistakes Students Make

• Using total electrons instead of per-atom valence
• Forgetting lone pairs
• Putting negative FC on the wrong atom (e.g., C instead of O)

🧠 Which Lewis Structure is More Stable?

Look at these two versions of OCN⁻ — both have total FC = 0. Which is better?

Structure A FC: O = 0, C = 0, N = 0
Negative charge on C

Structure B FC: O = -1, C = 0, N = 0
Negative charge on O (more electronegative)

⚡ One Line Tip:

Always give negative FC to the atom that loves electrons the most — oxygen, not carbon!

🧠 Practice Question

What is the formal charge on N in NH₄⁺?

✏️ Formula = Valence – (Lone Pairs + ½ Bonding Electrons) — Lock it in!