1. 1
   A nuclear medicine technician prepares a radioactive isotope of iodine for use in a hospital scan. Before administering it, the technician reviews the basic structure of the atom, including the positions, relative masses and relative charges of the subatomic particles it contains.

   (a)

   In which part of the atom are the protons and neutrons located?

   [1 mark]

   • AIn shells surrounding the atom
   • BOutside the atom
   • CSpread evenly throughout the whole atom
   • DIn the nucleus

   (b)

   What is the relative charge of an electron?

   [1 mark]

   • A+1
   • B0
   • C-1
   • D+2

   (c)

   Describe the structure of an atom in terms of the positions, relative masses and relative charges of protons, neutrons and electrons.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A scientist analyses two samples of chlorine gas from different sources using a mass spectrometer and finds that both samples contain a mixture of chlorine-35 and chlorine-37 atoms, but in slightly different proportions.

   (a)

   Chlorine-35 and chlorine-37 are described as isotopes of chlorine. What does this mean?

   [1 mark]

   • AThey have the same number of protons but different numbers of neutrons
   • BThey have the same number of neutrons but different numbers of protons
   • CThey have different numbers of protons and different numbers of neutrons
   • DThey have different numbers of electrons but the same number of protons and neutrons

   (b)

   How many neutrons are there in an atom of chlorine-37, given that chlorine has an atomic number of 17?

   [1 mark]

   • A17
   • B20
   • C37
   • D54

   (c)

   Explain why chlorine-35 and chlorine-37 are both atoms of the same element, chlorine, even though they have different mass numbers.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A mass spectrometer analysis of a sample of magnesium shows that it consists of three isotopes: magnesium-24 (79% abundance), magnesium-25 (10% abundance) and magnesium-26 (11% abundance).

   (a)

   Using magnesium as an example, explain what is meant by the terms atomic number and mass number.

   [3 marks]

   (b)

   Calculate the relative atomic mass (Ar) of this sample of magnesium, using the isotopic abundance data given, showing your working.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An archaeologist sends a sample of an ancient wooden artefact for carbon dating, a technique based on measuring the amount of the isotope carbon-14 remaining in the sample. Natural carbon is a mixture of three isotopes: carbon-12 (98.9% abundance), carbon-13 (1.1% abundance) and a negligible trace of carbon-14.

   (a)

   An archaeologist uses carbon dating, based on the isotope carbon-14, to estimate the age of an ancient wooden artefact. Describe fully the structure of an atom of carbon-12, stating the number, relative position, relative mass and relative charge of each type of subatomic particle it contains.

   [6 marks]

   (b)

   Explain why carbon-12, carbon-13 and carbon-14 are all classed as isotopes of the same element, why they have identical chemical properties, and calculate the relative atomic mass of carbon using the abundances given (treat the carbon-14 abundance as negligible and ignore it in the calculation).

   [6 marks]

   Total for question 4: 12 marks

End of questions