Why are the Group 0 noble gases so unreactive, and how do their properties vary?
Group 0 the noble gases: their lack of reactivity explained by full outer shells, the trends in boiling point and density down the group, and their uses.
A focused answer to Edexcel GCSE Chemistry topic 6, covering why the Group 0 noble gases are unreactive in terms of their full outer shells, the trends in boiling point and density down the group, that they are monatomic gases, and their uses such as in lighting and inert atmospheres.
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What this dot point is asking
Edexcel wants you to explain why the Group 0 noble gases are unreactive in terms of their full outer shells, describe the trends in boiling point and density down the group, recall that they are monatomic gases, and give their uses. The inertness explanation and the boiling-point trend are the common marks.
Why the noble gases are unreactive
This stability is the reason every other group reacts to achieve a full outer shell like a noble gas: Group 1 loses an electron, Group 7 gains one, and so on. The noble gases already have it, so they stay unreacted. Because they do not gain, lose or share electrons, the noble gases do not form ions and almost never form compounds, which is why they were discovered late (they give no obvious chemical reactions) and why they are sometimes called the inert gases.
Physical properties and trends
The noble gases are colourless gases at room temperature and exist as single atoms (monatomic), not molecules, because they do not need to bond. Going down the group:
You can use these trends to predict a missing value by interpolating between two known data points.
Uses of the noble gases
Their inertness and physical properties make them useful:
- Helium has a very low density and is non-flammable, so it is used to fill balloons and airships.
- Argon is used to provide an inert atmosphere inside filament light bulbs (so the hot filament does not burn away) and in welding (to stop the hot metal reacting with air).
- Neon and the other noble gases are used in coloured lighting and signs, glowing characteristic colours when a current passes through them.
- Helium is also used in deep-sea diving gas mixtures and to cool the superconducting magnets in MRI scanners, because it stays a gas (or liquid) at very low temperatures and is unreactive.
In every case it is the lack of reactivity that matters: the noble gas surrounds or fills something without reacting with it, which would be impossible with a reactive gas such as oxygen.
Try this
Q1. Explain why the noble gases are unreactive. [1 mark]
- Cue. They have a full outer shell of electrons, so they have no tendency to gain, lose or share electrons.
Q2. State the trend in boiling point down Group 0. [1 mark]
- Cue. The boiling point increases down the group.
Q3. Give one use of argon and explain why its inertness is important for that use. [2 marks]
- Cue. In light bulbs (or welding); it does not react with the hot filament (or metal), so the filament does not burn away.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 20193 marksExplain why the noble gases in Group 0 are very unreactive, and state why this makes argon suitable for use inside filament light bulbs.Show worked answer →
A 3-mark unreactivity-and-use question.
The noble gases are unreactive because they have a full outer shell of electrons (1 mark), so they have no tendency to gain, lose or share electrons and do not need to react to become stable (1 mark). Argon is used in filament light bulbs because it is inert, so it does not react with the hot metal filament, which stops the filament burning away (1 mark).
Markers reward "full outer shell" as the reason for inertness and linking the use to argon not reacting with the filament.
Edexcel 20213 marksDescribe the trend in boiling point of the noble gases down Group 0, and use the data that helium has a boiling point of and argon to predict whether the boiling point of neon (between them) is closer to or .Show worked answer →
A 3-mark trend-and-prediction question.
The boiling point increases down Group 0 (1 mark). Neon lies between helium () and argon (), so its boiling point must be between these two values (1 mark). Of the two options, lies between and , so the boiling point of neon is closer to (1 mark, as is outside the range).
Markers reward the increasing trend and using it to interpolate a value between the two given data points.
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Sources & how we know this
- Pearson Edexcel GCSE (9-1) Chemistry (1CH0) specification — Pearson Edexcel (2016)