Lone pair — Science definition

Defined in 2 courses:

A pair of valence electrons on an atom that is not shared in a bond. (Physical Science: Chemistry)
A valence electron pair not represented as a bond. (Physical Science: Chemistry)

Where it is taught

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

Questions using lone pair

Problem 1

Explain the difference between a bonding pair and a lone pair of electrons.

Answer and explanation

A bonding pair is a pair of electrons shared between two atoms, forming a covalent bond. A lone pair is a pair of valence electrons on a single atom that is not shared and does not form a bond.

Problem 2

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 3

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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