Noble Gases Exam Questions

• Noble gases have a full outer electron shell / a stable electron configuration (2 for He, 8 for the others) [1]
• They have no tendency to lose, gain, or share electrons, so they do not form bonds with other atoms [1]

Examiner note: “They are stable” alone is worth 0 marks — you must explain WHY they are stable (full outer shell). The full outer shell means there is no driving force to form chemical bonds.

(a) Filling balloons / airships / weather balloons — because helium is less dense than air (provides lift) and is non-flammable (safer than hydrogen) [1]

(b) Advertising signs / neon lights — because neon glows red-orange when an electric current is passed through it [1]

(c) Filling light bulbs / welding — because argon is unreactive (inert), so it prevents the hot filament or metal from oxidising [1]

Examiner note: Each use is linked to a specific property: helium = low density + inert; neon = emits coloured light; argon = inert atmosphere. Argon is used over nitrogen in some applications because it is denser and provides better protection.

(a) Boiling point increases down Group 0 [1]

(b) Going down the group, the atoms get larger / have more electrons [1]. This means stronger van der Waals / intermolecular forces between atoms, so more energy is needed to separate them [1].

Examiner note: Noble gases exist as single atoms (monatomic). The only forces between them are weak van der Waals forces. Larger atoms with more electrons have stronger van der Waals forces, hence higher boiling points. This is the same trend as in the halogens.

(a) 2 [1]

(b) 2, 8 [1]

Examiner note: Helium has only 2 electrons (full first shell). Neon has 10 electrons arranged as 2, 8 (both shells full). Argon has 18 electrons: 2, 8, 8. In each case, the outer shell is complete — this is why they are unreactive.

• Hydrogen is highly flammable / explosive when mixed with air [1]
• Helium is chemically inert / unreactive, so it does not burn or explode [1]
• Although hydrogen is slightly less dense (providing more lift), the safety advantage of helium far outweighs the small difference in lift [1]

Examiner note: The Hindenburg disaster (1937) demonstrated the danger of hydrogen-filled airships. Helium has a density of 4 g/mol (vs 2 g/mol for H2), so it provides slightly less lift, but the safety benefit is critical. This is a good example of evaluating risks and benefits.

(a) Because they do not react with other elements, they cannot be detected by the usual chemical tests / they do not form compounds that could be identified [1]

(b) “Inert” means completely unreactive, but some noble gas compounds (e.g. xenon fluorides) have been made under extreme conditions, so “inert” was inaccurate [1]. “Noble” means they rarely react, similar to noble metals like gold and platinum, which is a more accurate description [1].

Examiner note: The discovery of XeF2 and other xenon compounds in the 1960s showed that noble gases are not truly inert — just very reluctant to react. The term “noble gases” (or Group 0 / Group 18) is now standard.