1. 1
   A hospital's nuclear medicine department uses two forms of the element iodine: iodine-127, which is stable, and iodine-131, which is radioactive and used in some treatments. Both forms have the same proton number (53) but different nucleon numbers.

   (a)

   What term describes these two different forms of the same element?

   [1 mark]

   • AIsotopes
   • BIsomers
   • CIons
   • DAllotropes

   (b)

   Iodine-127 has a nucleon number of 127 and iodine-131 has a nucleon number of 131, both with a proton number of 53. How many more neutrons does an atom of iodine-131 have compared with an atom of iodine-127?

   [1 mark]

   • A131
   • B2
   • C53
   • D4

   (c)

   Explain why iodine-127 and iodine-131 have identical chemical properties, even though one is radioactive and the other is not.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A geologist analyses a rock sample and finds it contains carbon atoms of two different types: carbon-12 and carbon-14, both with a proton number of 6.

   (a)

   What can be concluded about the number of protons in an atom of carbon-14 compared with an atom of carbon-12?

   [1 mark]

   • ACarbon-14 has 2 fewer protons than carbon-12
   • BCarbon-14 has 2 more protons than carbon-12
   • CThey have the same number of protons
   • DCarbon-14 has no protons at all

   (b)

   Given that carbon-12 has a nucleon number of 12 and carbon-14 has a nucleon number of 14, how many neutrons does an atom of carbon-14 contain?

   [1 mark]

   • A6
   • B8
   • C14
   • D20

   (c)

   Define the term isotopes, and state, using carbon-12 and carbon-14 as your example, one way in which the two isotopes are the same and one way in which they are different.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A metallurgical company analyses a sample of naturally occurring copper and finds it contains two isotopes: copper-63 (69.2% abundance) and copper-65 (30.8% abundance).

   (a)

   Explain what information the mass number (nucleon number) of each isotope gives you, and explain why the two copper isotopes have different masses despite being atoms of the same element.

   [3 marks]

   (b)

   The company's data shows that the sample of naturally occurring copper is 69.2% copper-63 and 30.8% copper-65. Calculate the relative atomic mass of this sample of copper, showing your working, and give your answer to one decimal place.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A nuclear power plant uses uranium fuel enriched to increase the proportion of the isotope uranium-235, while most naturally occurring uranium is the isotope uranium-238, both with a proton number of 92.

   (a)

   Explain fully what is meant by isotopes, describe how the atomic structure of uranium-235 and uranium-238 differs, explain why both isotopes have the same chemical reactivity, and outline why, despite this identical chemical behaviour, physical and nuclear processes can still be used to separate the two isotopes from one another during enrichment.

   [6 marks]

   (b)

   The power plant's quality control laboratory represents one sample of enriched uranium using the symbol $^{235}_{92}$U. A trainee scientist mistakenly claims that because uranium-235 and uranium-238 have different nucleon numbers, they must also have different numbers of protons and therefore different chemical properties. Evaluate whether the trainee's claim is correct, explaining fully the relationship between proton number, nucleon number and neutron number, and the relationship between electronic configuration and chemical properties.

   [6 marks]

   Total for question 4: 12 marks

End of questions