Explain why the noble gases are described as inert, and explain why boiling point increases down Group 0.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Noble gases are inert because they possess a complete outer electron shell, so they have no tendency to gain, lose or share electrons and therefore do not form bonds.
Boiling point rises down Group 0 because the atoms become larger, with more electron shells. The increased size gives rise to stronger London dispersion forces between atoms, requiring more energy to separate them and so the boiling point is higher.
Boiling point rises down Group 0 because the atoms become larger, with more electron shells. The increased size gives rise to stronger London dispersion forces between atoms, requiring more energy to separate them and so the boiling point is higher.
Examiner tips
- Use the term "full outer shell" to justify inertness. Show the link between larger size, more electrons and stronger London forces. Keep the answer concise – one sentence for each part.
- Mention that the increase is due to London dispersion forces, not dipole–dipole or hydrogen bonding.
Common mistakes
- Confusing inertness with lack of reactivity in all conditions. Forgetting to mention London dispersion forces as the cause of higher boiling points. Using vague phrases like "more stable" without explaining the electron configuration.
Mark scheme (4 marks)
- Noble gases are inert / unreactive because they have a full outer shell of electrons
- A full outer shell means noble gases do not need to gain, lose, or share electrons (to form bonds / compounds)
- Boiling point increases down Group 0 because the atoms get larger / have more electrons / more electron shells
- Larger atoms have stronger intermolecular forces (between atoms), so more energy is needed to overcome them / separate the atoms
Key terms in this question
inert · noble gases · boiling point