Explain why the noble gases in Group 0 of the periodic table are described as chemically inert, and describe the trend in boiling points of the noble gases as you go down Group 0, explaining why this trend occurs.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
The noble gases include helium, neon, argon, krypton and xenon. They are widely used in industry and everyday life, for example in lighting and as inert atmospheres for welding.
Model answer (5 marks)
Noble gases have a full outer electron shell – eight electrons for all except helium, which has two.
Because the outer shell is full, they neither need to gain, lose nor share electrons, so they do not form chemical bonds and are chemically inert.
Boiling points rise down Group 0: He < Ne < Ar < Kr < Xe.
As you go down the group the atoms become larger and contain more electrons.
The larger electron cloud gives stronger London dispersion (van der Waals) forces between atoms, requiring more energy to overcome them and therefore a higher boiling point.
Because the outer shell is full, they neither need to gain, lose nor share electrons, so they do not form chemical bonds and are chemically inert.
Boiling points rise down Group 0: He < Ne < Ar < Kr < Xe.
As you go down the group the atoms become larger and contain more electrons.
The larger electron cloud gives stronger London dispersion (van der Waals) forces between atoms, requiring more energy to overcome them and therefore a higher boiling point.
Examiner tips
- State that a full valence shell gives inertness; mention the 8‑electron rule. Explain the trend in boiling points by citing increasing London dispersion forces. Use the correct order of elements and the term ‘van der Waals forces’. Keep the answer concise – 5 marks only.
- common_mistakes
- :
- Saying the gases are inert because they have no bonds, without mentioning the full valence shell. Confusing the trend (e.g., claiming boiling points decrease). Using vague terms like ‘big atoms’ instead of ‘more electrons’ and ‘stronger dispersion forces’.
Mark scheme (5 marks)
- Noble gases have a full outer shell of electrons (eight electrons in the outer shell, or two for helium)
- Because the outer shell is full, noble gases do not need to gain, lose, or share electrons, so they do not form chemical bonds / do not react
- Boiling points increase as you go down Group 0 (from helium to xenon)
- As you go down the group, the atoms have more electrons / are larger
- More electrons means stronger intermolecular forces (London dispersion forces / van der Waals forces) between atoms, so more energy is needed to overcome them, giving a higher boiling point
Key terms in this question
noble gases · Group 0 · chemically inert · boiling point
Related
- All Edexcel A-Level Chemistry (9CH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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