1. 1
   A lighting engineer is selecting gases to fill glass tubes for illuminated signs. She needs a gas that will glow with a distinctive colour when electricity passes through it, but will not react with the metal electrodes or the glass over the tube's lifetime. She is comparing neon, argon and krypton, all found in Group 0 of the periodic table.

   (a)

   A lighting engineer is choosing gases to fill different types of signage tubes. She is told that Group 0 elements are chosen because they do not react with the hot filament or electrodes inside the tube. Which term describes elements that do not readily take part in chemical reactions?

   [1 mark]

   • AReactive
   • BInert
   • CCorrosive
   • DVolatile

   (b)

   The engineer notes that neon, argon and krypton are all found in the same group of the periodic table. What is true of the number of electrons in the outer shell of every Group 0 element?

   [1 mark]

   • AIt is always 1
   • BIt is always 7
   • CIt is a full outer shell
   • DIt varies randomly between elements

   (c)

   Explain, in terms of electronic structure, why neon, argon and krypton are all unreactive and therefore suitable for use in the sign tubes.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A commercial diving company supplies its divers with breathing gas mixtures containing helium instead of nitrogen, because helium does not dissolve into body tissues in the same problematic way during deep dives. The company's technicians want to understand why helium, like the other Group 0 gases, is so unreactive and safe to breathe in these mixtures.

   (a)

   A deep-sea diving company fills its divers' breathing cylinders with a mixture of oxygen and helium instead of oxygen and nitrogen, because helium is far less likely to dissolve into the diver's blood in a way that causes problems on ascent. Helium is found in Group 0. Which of these best describes helium's position relative to the other noble gases?

   [1 mark]

   • AHelium has the highest relative atomic mass in the group
   • BHelium has 8 outer electrons like the other noble gases
   • CHelium is a halogen, not a noble gas
   • DHelium is at the top of Group 0, with the lowest relative atomic mass

   (b)

   The technicians also compare the boiling points of the noble gases used in different depths of diving equipment. Which statement correctly describes the trend in boiling point down Group 0?

   [1 mark]

   • ABoiling point increases going down the group
   • BBoiling point stays the same for all noble gases
   • CBoiling point decreases going down the group
   • DBoiling point changes randomly with no clear trend

   (c)

   The company observes that argon has a higher boiling point than helium. Explain why boiling point increases going down Group 0, referring to relative atomic mass.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A museum conservation team is designing sealed display cases for a collection of ancient bronze and iron artefacts. To prevent the metals from corroding further, the team considered several gases to fill the cases, including ordinary air, nitrogen and argon, before deciding to use argon.

   (a)

   A museum uses argon gas to fill the sealed display cases that protect ancient metal artefacts from corrosion. Explain why argon is a suitable gas to use for this purpose instead of ordinary air.

   [3 marks]

   (b)

   The conservation team also considered using nitrogen gas instead of argon, since nitrogen is cheaper to obtain in large quantities. Explain why nitrogen, although fairly unreactive, would be a less ideal choice than argon in terms of its electronic structure and typical reactivity, and describe one practical advantage argon-filled cases give the museum.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An electrical engineer at a national grid operator is investigating gases for use inside high-voltage switching equipment. The equipment must prevent electrical arcs from forming between components and must not corrode the metal parts inside the sealed unit over a 25-year operating lifetime. The engineer is comparing the properties of noble gases with other atmospheric gases to decide which would perform best.

   (a)

   A national grid operator is designing high-voltage circuit breakers that use sulfur hexafluoride gas to quench electrical arcs, and is considering whether noble gases such as argon could serve a similar insulating role in some components. Discuss, with reference to electronic structure, why noble gases are excellent electrical insulators and why they are widely used in situations where preventing unwanted chemical reactions or electrical discharge is important, giving at least one other real-world application of a noble gas.

   [6 marks]

   (b)

   The grid operator's engineer also needs to justify, for a safety report, why the specific choice of noble gas matters even though all Group 0 elements share a full outer shell. Explain how properties such as boiling point and relative atomic mass differ down Group 0, and evaluate why these physical property trends, rather than reactivity, would determine the engineer's final choice between helium, neon and argon for use at normal atmospheric pressure and typical UK ambient temperatures.

   [6 marks]

   Total for question 4: 12 marks

End of questions