Noble Gases – IGCSE Chemistry Definition
IGCSE Chemistry definition of noble gases: Group 0 elements with full outer electron shells. Covers properties, uses, and exam tips for Cambridge 0620.
Published by IGCSEChemistry.com.my
Chemistry teaching team: K. S. Tan (15+ years teaching IGCSE Chemistry) and Ms Yash (10+ years teaching IGCSE Chemistry) and Ms Kartini (15+ years teaching IGCSE Chemistry).
Mapped to Cambridge IGCSE Chemistry 0620 (2026–2028). Last updated 2026-08-19.
Group 0 is a short topic, but it carries guaranteed marks. Paper 1 and Paper 2 regularly ask why noble gases are unreactive and what they are used for. The link between their full outer shell and their lack of reactivity is the key idea.
The 0620 definition
The noble gases are the elements in Group 0 of the periodic table: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). They have a full outer electron shell, making them very stable and unreactive.
Electron configurations
| Noble gas | Electron configuration | Outer shell |
|---|---|---|
| He | 2 | Full (2) |
| Ne | 2, 8 | Full (8) |
| Ar | 2, 8, 8 | Full (8) |
The stability of the full outer shell is the reason other elements react — metals lose electrons and non-metals gain electrons to achieve noble gas configurations.
Physical properties
- All are colourless, odourless gases at room temperature
- Exist as single atoms (monatomic), not molecules — they do not form bonds
- Boiling points increase down the group (He: −269 °C, Rn: −62 °C) as van der Waals forces increase with atomic size
- Very low densities
Uses of noble gases
| Noble gas | Use | Why |
|---|---|---|
| Helium | Balloons, airships | Very light (low density), non-flammable |
| Neon | Advertising signs (red glow) | Glows red-orange when electricity passes through |
| Argon | Filament light bulbs, welding | Unreactive — prevents the hot filament or metal from oxidising |
| Krypton/Xenon | Specialised lighting | Produce bright white light |
The common thread: their unreactivity makes them safe to use in environments where reactive gases would cause problems.
Worked exam question
Argon is used in filament light bulbs. (a) State the group of argon in the periodic table. [1] (b) Explain why argon is used instead of air. [2]
Mark scheme
(a) Group 0 [1]
(b) Argon is unreactive / inert [1]; so it does not react with the hot tungsten filament / prevents oxidation of the filament [1]
Common exam mistakes
- Calling Group 0 “Group 8” — the IGCSE syllabus uses Group 0.
- Saying noble gases are unreactive because they have “no electrons” — they have a full outer shell, not an empty one.
- Writing He₂ or Ne₂ — noble gases are monatomic (single atoms), not diatomic.
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