Key Concepts
Formal Charges
Formula:
Formal charge = valence electrons − lone pair electrons − ½(bonding electrons).
Atoms with more bonds than usual get a positive formal charge; fewer bonds means negative.
Quick Patterns
Nitrogen
with 4 bonds → +1. With 2 bonds and a lone pair → −1.
Oxygen
with 3 bonds → +1. With 1 bond and 3 lone pairs → −1.
Carbon
with 3 bonds and a lone pair → −1. With 3 bonds and no lone pair (empty p) → +1.
Resonance & Formal Charges
Moving electrons between resonance forms changes where formal charges appear.
The total charge of the molecule stays the same across all resonance forms.
Formal charges help you track electron flow when drawing resonance arrows.
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Identify Partial Charges
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