Explain why scientists classify helium, neon, and argon as noble gases and describe one use of a noble gas that depends on its unreactive nature.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
The noble gases are found in Group 0 of the periodic table. They make up a small but important fraction of the Earth's atmosphere and have several practical applications in everyday life.
Model answer (5 marks)
Helium, neon and argon are classified as noble gases because they have a full outer electron shell (helium 2s², neon 2s²2p⁶, argon 3s²3p⁶). A full outer shell means they have no tendency to gain, lose or share electrons, so they are chemically unreactive or inert. One use that relies on this inertness is argon in incandescent light bulbs: argon gas is introduced into the bulb to prevent the tungsten filament from oxidising at high temperature, thereby extending the bulb’s life.
Examiner tips
- Use the exact phrase ‘full outer shell’ and explain its consequence (no electron transfer).
- State the inertness explicitly.
- Give a specific example and link the use to the inertness.
- Keep the answer concise to fit the 5‑mark limit.
Common mistakes
- Confusing ‘full outer shell’ with ‘full valence shell’ or omitting the electron configuration.
- Describing a use that does not depend on inertness, e.g. helium balloons, without linking it to the gas’s unreactivity.
Mark scheme (5 marks)
- Noble gases have a full outer shell of electrons
- Because their outer shell is full, they do not need to gain, lose, or share electrons
- Therefore noble gases are (chemically) unreactive / inert
- Correct named use of a noble gas, e.g. argon used in light bulbs / welding, helium used in balloons / airships, neon used in advertising signs
- The use described depends on the noble gas being unreactive / inert, so it does not react with the material or surroundings, e.g. argon in a light bulb prevents the filament from burning/oxidising
Key terms in this question
Related
- All OCR A-Level Chemistry B: Salters (H433) revision notes →
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- Decode the mark scheme abbreviations →
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