Formal charge — Science definition

An electron-counting assignment, distinct from partial charge.

Where it is taught

Lewis Structures, Resonance & Bond Models — Bonding, Formulas & Molecular Structure, Physical Science: Chemistry, Grade 11

In use

Formal charge is bookkeeping: valence electrons minus nonbonding electrons minus half of bonding electrons.
Lewis Structures, Resonance & Bond Models

Questions using formal charge

Problem 1

For NH₄⁺, count valence electrons, assign nitrogen’s formal charge for four N–H single bonds and no lone pair, and distinguish that charge from molecular shape.

Answer and explanation

Total valence electrons are 5+4(1)−1=8. Nitrogen formal charge is 5−0−4=+1 and each H is zero. The flat Lewis connectivity does not specify measured angles; the common molecular arrangement is tetrahedral.

Response criteria

Use the stated measurements or conditions, with correct units.
Connect the result to the chemical mechanism or evidence relationship.
Identify the assumption, model limit or further evidence requested.

Problem 2

Independent chapter check: For NH₄⁺, count valence electrons, assign nitrogen’s formal charge for four N–H single bonds and no lone pair, and distinguish that charge from molecular shape.

Answer and explanation

Response criteria

Use the stated measurements or conditions, with correct units.
Connect the result to the chemical mechanism or evidence relationship.
Identify the assumption, model limit or further evidence requested.

Taught alongside

Elsewhere

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