8.5The Periodic Table
Noble gases — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions
5 min read 11 parts Lesson 5 of 5 Unit quiz
Lesson summary
8.5 Noble gases — Notes — IGCSE Chemistry notes: Describe the properties, electronic configurations, trends, unreactivity and uses of the noble gases.Position — Group 0 (also called Group VIII in older tables), on the right of the Periodic Table.Elements — helium, neon, argon, kr…
- Inert atmosphere
- Filament lamp
- Helium compared with hydrogen
- Neon, krypton and xenon
- Full outer shell
- Elements — helium, neon, argon, krypton and xenon
Part 1 of 9The noble gases
Position
- Group 0 , on the right of the Periodic Table.
- (also called Group VIII in older tables)
Elements
- Elements helium, neon, argon, krypton and xenon.
They are non-metals.
Radon
- Radon it is also a noble gas, and it is radioactive.
Part 2 of 9Physical properties
Colourless gases at room temperature.
Monatomic
- Monatomic each particle is a single atom rather than a molecule of two or more atoms.
Melting and boiling points are very low, because the attractions between separate atoms are weak.
They are poor conductors of heat and electricity.
Helium has a boiling point of about −269 °C.
Part 3 of 9Trends down the group
Trends down the group
Boiling point increases because the atoms get larger.
Density increases.
The forces between atoms are stronger in larger atoms, which is why the boiling point increases.
Part 4 of 9Electronic configurations
| Gas | Electron arrangement |
|---|---|
| Helium | 2 (a full first shell) |
| Neon | 2,8 |
| Argon | 2,8,8 |
| Krypton | 2,8,18,8 |
| Xenon | 2,8,18,18,8 |
- The outer shell is full, with two electrons in helium and eight electrons in the others, so not every noble gas has eight outer electrons.
Part 5 of 9Why they are unreactive
1
A full outer shell gives an extremely stable electron arrangement.
2
They have little tendency to gain, lose or share electrons, so they do not easily form bonds with other elements.
3
They are much less reactive than most other elements and are commonly described as inert.
4
Neon (2,8) has a complete outer shell, so it rarely forms compounds.
Part 6 of 9Uses of the noble gases
| Gas | Use | Reason |
|---|---|---|
| Helium | Balloons and airships; cooling MRI scanners; breathing mixtures for deep-sea divers | Low density, non-flammable and unreactive |
| Neon | Red-orange advertising signs and lasers | Glows when electricity is passed through |
| Argon | Filament light bulbs and welding | Unreactive, so the filament does not burn |
| Krypton | Lasers and some lighting | Unreactive and glows in discharge tubes |
| Xenon | Car headlamps and flash lamps | Produces bright light in discharge tubes |
Part 7 of 9Why unreactive gases are useful
1Inert atmosphere
- Inert atmosphere because they do not react, other materials will not oxidise in them.
2Filament lamp
- Filament lamp a tungsten wire would burn in air at its operating temperature, but argon prevents this.
3Welding
- Welding an argon shield stops hot metal reacting with oxygen.
4Helium compared with hydrogen
- Helium compared with hydrogen helium is safer for lifting because it is non-flammable.
Part 8 of 9Sources and occurrence
Argon
- Argon the third most abundant gas in dry air, at about 0.9%.
Helium
- Helium obtained from natural gas.
Neon, krypton and xenon
- Neon, krypton and xenon obtained by fractional distillation of liquid air.
Radon
- Radon radioactive and a health risk where it builds up inside buildings.
Part 9 of 9More from the specification
More from the specification
Closed electron shells in noble gases
- Closed electron shells in noble gases completely filled valence electron shells prevent chemical reactivity,
- allowing condensation into monoatomic solid crystals only near absolute zero.
Chemical Inertness of Group VIII / 0 Elements
- Noble gases possess complete, stable valence electron octets (or a duplet in helium), making them monatomic and virtually chemically unreactive.
- (He, Ne, Ar, Kr, Xe)
Trends in Boiling Point and Density Down Group VIII
- As atomic mass and the number of electrons increase down the group, weak London dispersion forces between atoms strengthen,
- causing boiling points and gas densities to increase progressively.
Practical Applications Based on Inertness
- Helium is used to fill airships and weather balloons due to its low density and non-flammability, argon provides an inert protective shielding atmosphere in electric light bulbs and arc welding,
- and neon emits characteristic light in advertising signs.
Transition elements
- The central block of metals between Group II and Group III.
Alkali metals
- The Group I metals, which form alkaline solutions with water.
Physical property
- A property observed or measured without changing the material.
Halogens
- Group 17 non-metals that form diatomic molecules.
Halogen
- A Group VII non-metal with seven outer electrons.
Observation
- What is seen, heard, smelt or measured
Aqueous
- Dissolved in water.
Displacement
- A reaction in which a more reactive element takes the place of a less reactive one in a compound.
Key terms
| Term | Meaning |
|---|---|
| Noble gas | an unreactive Group 0 element with a full outer shell. |
| Monatomic | existing as single atoms. |
| Inert | very unreactive and not forming compounds. |
| Full outer shell | an outer shell holding the maximum number of electrons, which is stable. |
| Inert atmosphere | a gas environment in which other materials will not react. |
Avoid these mistakes
1
Saying noble gases are unreactive only because they are stable — the reason is a full outer shell of electrons
2
Saying noble gases have eight outer electrons — helium has two
3
Saying noble gases are diatomic or molecules — they are monatomic non-metals
4
Mixing up the direction of the trend in boiling point — it increases down the group
5
Describing helium as flammable — it is non-flammable
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