Explain the low reactivity of nitrogen
Connect nitrogen's limited reactivity with the strong, non-polar triple bond in N₂.
AS Level; Cambridge International Chemistry 9701, 2025–2027 syllabus. Explain the stated molecular, acid–base and atmospheric reaction pathways; balance equations and distinguish direct reactions from catalytic cycles. Written practice is self-checked
Before you begin
- Use covalent bond order, lone pairs, Brønsted–Lowry proton transfer, oxidation numbers and balanced equations.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which bond is present within a nitrogen molecule?
What you will learn
- Identify the N≡N triple bond
- Relate bond strength to the energy needed for reaction
- Explain why the non-polar molecule is not readily attacked by polar reagents
Nitrogen molecules contain a strong triple bond
Each N₂ molecule contains an N≡N triple covalent bond. The bond is short and requires substantial energy to break, so many reactions involving N₂ have a high activation-energy barrier.
The large energy needed to disrupt this bond helps explain why nitrogen gas is relatively unreactive under ordinary conditions. It does not mean nitrogen can never react: suitable energy, pressure, catalysts or other conditions can make reactions occur.
The molecule is non-polar
The two atoms in N₂ are identical, so the bonding electrons are shared equally and the molecule has no permanent dipole.
The strong triple bond and lack of polarity are separate reasons: one makes bond breaking difficult; the other gives little electrostatic attraction to polar reagents. Do not claim non-polarity alone explains every reaction.
Pause and explain
Which combination explains the low reactivity of nitrogen gas?
Worked example
Explain why nitrogen gas is relatively unreactive at ordinary conditions.
Show the worked solution
- N₂ has a strong N≡N triple bond.
- Breaking this bond requires substantial energy and gives reactions a high activation barrier.
- N₂ is also non-polar, so polar reagents are not strongly attracted to it.
Answer Nitrogen is relatively unreactive because the strong N≡N triple bond is difficult to break and the non-polar molecule is not strongly attracted to polar reagents.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
State the bond and polarity of N₂.
Give me a hint
Compare the two identical nitrogen atoms and count the shared electron pairs.
Compare my reasoning
- The atoms share three pairs of electrons.
- This is an N≡N triple covalent bond.
- Identical atoms share equally, so N₂ is non-polar.
N₂ is a non-polar molecule containing an N≡N triple covalent bond.
Look for these in your work
- Triple bond identified
- Covalent sharing stated
- Polarity justified
Explain the bond-strength contribution to nitrogen's low reactivity.
Give me a hint
Link the energy needed to break the bond to the activation barrier.
Compare my reasoning
- The N≡N bond is very strong.
- Breaking it requires substantial energy.
- Many reactions therefore have a high activation-energy barrier.
The strong N≡N bond is difficult to break, so reactions that require its disruption have a high activation-energy barrier.
Look for these in your work
- Bond strength stated
- Energy link included
- Reactivity conclusion follows
A student says nitrogen cannot react because it is non-polar. Improve this explanation.
Give me a hint
Include the bond and avoid an absolute claim.
Compare my reasoning
- N₂ is non-polar, so polar reagents are not strongly attracted.
- Its N≡N triple bond is also very strong.
- Nitrogen can react under suitable conditions, so it is relatively rather than completely unreactive.
Nitrogen is relatively unreactive because N₂ is non-polar and contains a strong N≡N triple bond; reactions remain possible under suitable conditions.
Look for these in your work
- Polarity linked to attraction
- Bond strength included
- Absolute claim corrected
Common mistakes
- Saying the triple bond is weak because nitrogen is a gas
- Claiming nitrogen can never react
- Treating non-polarity as the only reason for low reactivity
What can you explain now?
Which bond is present within a nitrogen molecule?
Compare with the explanation
N≡N
Each N₂ molecule has a triple covalent bond.
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Make it stick
How do the N≡N bond and the polarity of N₂ contribute separately to its low reactivity?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.